- Pocket K No. 12: Delayed Ripening Technology
- Induced Ripening Agents and Their Effect on Fruit Quality of Banana
- Ethene (Ethylene)
- Uses of ethene (ethylene)
- Annual production of ethene (ethylene)
- Manufacture of ethene (ethylene)
- Ask an expert: Why do bananas ripen fruit?
- Fruit ripening and storage
- This Is the Secret to Storing Every Type of Fruit and Vegetable So They Last Longer
- Control of Ethylene in fruits & vegetables warehouses and cold stores
- Ethylene – The Ripening Hormone
- The Ethylene Effect
- Conventional Practices are Harmful for Fruits and Vegetables
- Why Ethylene Control!!!
- The Solution
- Fruits & Vegetables Producing Ethylene Or Sensitive To Ethylene
- Fruits Ripening Gas – Ethylene
- Ethylene Producing and Ethylene Sensitive Fruits & Vegetables
- Ethylene Producing Fruits & Vegetables
- NO Ethylene Emission, Not Sensitive
- Ethylene Sensitive Fruits & Vegetables
- Fruits & Vegetables That Produce Ethylene
- Fruits & Vegetables Sensitive To Ethylene
- Fruits & Vegetables that DO NOT Produce Ethylene Gas
- We may be partial, but we think fruit ripening is the noblest of all ethylene’s uses. We hope you find our ethylene fact sheet helpful and informative.
- Ethylene gas safe for ripening banana
- We Make Safety a Priority
- Other reasons why our ethylene generators and Ethy-Gen® II Ripening Concentrate are superior:
- There’s a reason that ripeners all across the world choose the ethylene application products of Catalytic Generators Australia. Our generators are the safest, our Ethy-Gen® II is the best, our customer service is quick and our products are easy to use. And that’s the simple truth. Give us a try today.
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Pocket K No. 12: Delayed Ripening Technology
Ripening is a normal phase in the maturation process of fruits and vegetables. Upon its onset, it only takes about a few days before the fruit or vegetable is considered inedible. This unavoidable process brings significant losses to both farmers and consumers alike.
Scientists have been working to delay fruit ripening so that farmers will have the flexibility in marketing their goods and ensure consumers of “fresh-from-the-garden” produce.
The Fruit Ripening Process
Ethylene is a natural plant hormone associated with growth, development, ripening and aging of many plants. This phytohormone is said to promote ripening in a variety of fruits including bananas, pineapples, tomatoes, mangoes, melons, and papayas. It is produced in varying quantities depending on the type of fruit. But when the concentration of ethylene reaches 0.1-1.0 ppm (parts per million), the ripening process in climacteric fruits is considered irreversible.
Climacteric fruits are usually harvested once they have reached maturity which then undergoes rapid ripening during transit and storage. Important tropical fruits such as banana, mango, papaya, pineapple and guava are examples of these fruits. Non-climacteric fruits do not ripen after harvest. Thus, in order to attain full ripeness and flavor, these fruits such as strawberries and oranges, are often harvested once they have fully ripened.
In tomatoes, it takes about 45-55 days for the fruit to reach full maturity. After which, it starts to undergo the ripening process. The production of ethylene within the fruit in turn signals the activity of different enzymes resulting in physiological changes such as change of color from green to red, softening of the fruit, and development of its distinct taste and aroma.
Normally, farmers pick their produce while they are still green. The ripening process is then induced by spraying the fruits or vegetables with ethylene gas when they reach their destination. For long hauls, fruits and vegetables are refrigerated to prevent damage and delay ripening.
However, there are drawbacks to these post harvest practices. Fruits that have been harvested prematurely may result in poor taste and quality despite appearing as fully ripened ones. Fruits transported for long periods under refrigeration also have the tendency to lose their quality.
Controlling the Ripening Process
There are several ways by which scientists can control the ripening process by genetic modification.
Regulation of Ethylene Production
The amount of ethylene produced can be controlled primarily by “switching off” or decreasing the production of ethylene in the fruit and there are several ways to do this. They include:
a. Suppression of ACC synthase gene expression.ACC (1-aminocyclopropane-1-carboxylic acid) synthase is the enzyme responsible for the conversion of S-adenosylmethionine (SAM) to ACC; the second to the last step in ethylene biosynthesis. Enzyme expression is hindered when an antisense (“mirror-image”) or truncated copy of the synthase gene is inserted into the plant’s genome.
b. Insertion of the ACC deaminase gene.The gene coding for the enzyme is obtained from Pseudomonas chlororaphis, a common nonpathogenic soil bacterium. It converts ACC to a different compound thereby reducing the amount of ACC available for ethylene production.
c. Insertion of the SAM hydrolase gene.This approach is similar to ACC deaminase wherein ethylene production is hindered when the amount of its precursor metabolite is reduced; in this case, SAM is converted to homoserine. The gene coding for the enzyme is obtained from E. coli T3 bacteriophage.
d. Suppression of ACC oxidase gene expression. ACC oxidase is the enzyme which catalyzes the oxidation of ACC to ethylene, the last step in the ethylene biosynthetic pathway. Through anti-sense technology, down regulation of the ACC oxidase gene results in the suppression of ethylene production, thereby delaying fruit ripening.
Control of Ethylene Perception
Since ethylene signals the onset of fruit ripening, delayed ripening on some plants can be achieved by modifying their ethylene receptors. The gene ETR1 is one example, and it has been shown to encode an ethylene binding protein. Plants with modified ETR1 lack the ability to respond to ethylene.
Suppression of Polygalacturonase Activity
Polygalacturonase (PG) is the enzyme responsible for the breakdown of pectin, the substance that maintains the integrity of plant cell walls. Pectin breakdown occurs at the start of the ripening process resulting in the softening of the fruit. To produce a fruit with DR trait using this method, scientists insert an anti-sense or a truncated copy of the PG gene into the plant’s genome resulting in a dramatic reduction of the amount of PG enzyme produced thereby delaying pectin degradation.
Advantages of DR Technology
The increased shelf life of products offers several advantages to both producers and consumers:
- Assurance of top quality fruits and vegetables on the market. Farmers can now wait for the fruits and vegetables to attain full maturity before they are plucked from their vines thereby allowing the fruits to exude full quality. Consumers will get value for their money.
- Widening of market opportunities for farmers as their produce can now be transported for longer periods of time, some of which would not even require refrigeration.
- Reduction in postharvest losses. DR fruits do not go soft easily compared to conventional ones and are therefore more resilient to damage during handling and transportation. This ensures a significant percentage of the harvested fruits to end up on the market shelves.
- Extension in shelf life as fruits or vegetables as they stay fresher and nutritious for longer periods. These fruits will not easily go “over the hill”.
Safety Aspects of DR Technology
The first ever GM crop approved for marketing was the Flavr-SavrTM tomato produced by Calgene, Inc. (U.S.) in 1994. After thoroughly studying DR technology and its products, US regulatory agencies concluded that the DR technology is safe, it produces tomatoes that have the same nutritional composition as the conventional ones and that show no difference in levels of allergens or toxins compared to normal fruit. In addition, field trials have shown that the DR tomatoes do not pose any threat to other plants nor to any non-target organisms.
Other DR tomatoes that followed thereafter have also been granted deregulated status by regulatory agencies in several countries including the U.S., Canada, and Mexico. In 1996, the UK’s food safety regulators also gave their thumbs up to a DR tomato developed by Zeneca Seeds but it is not currently being sold in supermarkets.
A European First
On February 5, 1996, branches of Safeway and Sainsbury’s supermarkets throughout the UK started to sell tomato pureé made from genetically-modified tomatoes. This was the first time that food made from a GM organism had been sold in Europe.
Labels on the cans clearly stated that the product had been made with GM tomatoes. Although there was no legal requirement to label the product, both supermarkets adopted an ‘open’ information policy from the start. For the inquisitive customer there was no shortage of information: leaflets were available describing the product, its benefits to the environment and consumer, the technology, and the regulatory processes through which the product had to pass.
According to the supermarkets, sales in around 80 stores in which supplies were initially available were brisk. Figures indicated that once they bought the product, shoppers came back for more. In November 1997, Safeway Stores announced that they had sold three quarters of a million cans of the product, and that average sales per store of the modified tomato purée exceeded those of the conventional equivalent. One reason might have been the price: the new purée cost 29 pence for 170 grams while the traditional form cost slightly more: 29 pence for a mere 142 grams.
Both supermarket chains pledged that the new product would always be offered alongside its old-fashioned counterpart. This move pleased consumer groups, which had no objection to the purée, provided that it was safe to eat and that consumers were always given a choice.
However, commercial pressures generated by public concern about GM foods early in 1999 forced Sainsbury’s to announce that it would withdraw the product from sale. Stocks were exhausted by July 1999.
Current Status of DR Technology
Delayed Ripening (DR) Technology has been applied for use in tomatoes, melons, and papaya. An interesting application of DR technology is in floriculture where experiments are underway to apply the technology to delay the withering of flowers.
In Southeast Asia, DR technology is being applied for use in papayas, a popular subsistence food and part of the general diet in the region. This technology could significantly increase the availability of this nutritious fruit to consumers and to small-scale and mostly resource-poor farmers in the region.
Regulatory approval of countries for crops with the DR trait.
|Crop||Countries||Type of Approval|
|Food, feed, cultivation
Food, feed, cultivation
Source: ISAAA GM Approval Database. http://www.isaaa.org/gmapprovaldatabase.
*Updated October 2018
Induced Ripening Agents and Their Effect on Fruit Quality of Banana
Ripening is a genetically programmed highly coordinated irreversible phenomenon which includes many biochemical changes including tissue softening, pigment changes, aroma and flavour volatile production, reduction in astringency, and many others. Banana is one of mostly consumed fruit crops in the world. Since banana is a climactic fruit, induced ripening is essential in commercial scale banana cultivation and distribution to assure good flavour, texture, and uniform peel colour. Ethylene gas, acetylene gas liberated from calcium carbide, and ethephon are some of the commercial ripening agents used successfully in the trade and they have been widely studied for their effectiveness on initiating and accelerating the ripening process and their effect on fruit quality and health related issues. Lauryl alcohol was also shown as a ripening agent for bananas. Most studies suggest that there is no difference in biochemical composition and sensory quality in bananas treated with chemicals that induce ripening from naturally ripened bananas. However volatile profiles of artificially ripened bananas were shown to be considerably different from naturally ripened bananas in some studies. This review discusses induced ripening agents and their effect on fruit quality of bananas.
1. Ripening Physiology
The life of a fruit can be divided into three phases: fruit set, fruit development, and fruit ripening. Fruit ripening is the initiation of fruit senescence which is a genetically programmed highly coordinated process of organ transformation from unripe to ripe stage to yield an attractive edible fruit . It is an irreversible phenomenon involving a series of biochemical, physiological, and organoleptic changes . These changes include changes in carbohydrate content, increment of sugar content, changes in colour, texture, aroma volatiles, flavour compounds, phenolic compounds, and organic acids.
Respiration is a process of breakdown of complex material in cells to simpler molecules giving energy and some specific molecules which are used in different cellular reactions. Thus respiration is a good indicator of cellular metabolic activity, and respiratory pattern is characteristic of the stages in the life cycle of a fruit such as development, ripening, and senescence . Fruit ripening is closely linked to ethylene, a phytohormone that can trigger initiation of ripening and senescence. Based on regulatory mechanisms leading to fruit ripening, fruits can be divided into two groups: climacteric and nonclimacteric fruits. Table 1 depicts classification of fruits as climacteric and non climacteric fruits. In climacteric fruits, as ripening proceeds there is a strong respiratory peak with high level of ethylene production. While in nonclimacteric fruits respiration rate is almost constant or shows a steady decline until senescence occurs, with little or no increase in ethylene production . Therefore, climacteric fruits are referred to as ethylene dependent fruits and they have the capability to ripen after the harvest, often with the help of exogenous ethylene. However it is generally claimed that nonclimacteric fruits ripen only if they remain attached to the parent plant . Respiratory pattern during ripening of several climacteric and non climacteric fruits are shown in the Figure 1.
Table 1 Classification of fruits as climacteric and nonclimacteric fruits (source ).
Respiratory pattern during ripening of climacteric and nonclimacteric fruits (source ).
The relationship between ethylene and fruit ripening has been studied for many decades. Although climacteric fruits are considered as ethylene dependent, it has been shown that in climacteric fruits some ripening changes occur independently of ethylene; also there are some changes in nonclimacteric fruits which are ethylene dependent. There are two systems of ethylene biosynthesis. System 1 represents ethylene biosynthesis during the preclimacteric stage of climacteric fruits as well as during the whole ripening process of nonclimacteric fruits. This is responsible for very low levels of ethylene production and is regulated in an autoinhibitory manner. System 2 operates during the ripening of climacteric fruit and is an autostimulated process which is responsible for high levels of ethylene production .
The ethylene biosynthesis pathway in higher plants has been well studied. Briefly, ethylene is synthesized from methionine. First methionine is converted to S-adenosyl-L methionine (SAM) which is catalyzed by SAM synthetase. Then SAM is converted to 1-aminocyclopropane-1-carboxylic acid (ACC). This conversion is catalyzed by the enzyme ACC synthase and then ACC is converted to ethylene catalyzed by ACC oxidase. Methionine is regenerated from ACC through the Yang cycle . Figure 2 shows the mechanism of ethylene biosynthesis from methionine.
The mechanism of ethylene biosynthesis from methionine.
The Arabidopsis model system was used to study the mechanism involved in ethylene perception and signal transduction. However, more efforts in understanding the ethylene response during fruit ripening have focused on the characterization of tomato homologs. In summary, ethylene is perceived by receptors (ETR) in endoplasmic reticulum (ER). Ethylene receptors are multigene families encoding two types of closely related proteins, one subfamily with a histidine kinase domain and the other subfamily with a serine/threonine kinase function . The receptors are negative regulators and in the absence of ethylene, constitutive Triple Response (CTR1) gets activated. CTR1 suppresses the ethylene response via inactivation of Ethylene Insensitive 2 (EIN2) . This activates a transcriptional cascade, involving Ethylene Insensitive 3 (EIN3)/Ethylene Insensitive 3 like 1 (EIL1) as the primary transcription factor and then ERFs, which in turn regulate genes underlying ripening related behavior .
2. Changes during Ripening
Compositional and structural changes occur during ripening leads to the fruit being desirable and edible. Among these changes, textural change is very important and a major event in fruit ripening. These textural changes differ with species where some fruits such as banana, mango, and papaya undergo substantial softening and fruits such as apple normally exhibit less softening. Textural changes and fruit softening are due to depolymerization and solubilization of cell wall components and loss of cell structure . Change in turgor pressure and degradation of cell wall polysaccharides and enzymatic degradation of starch are determinant mechanisms of fruit softening. Cell wall polysaccharides such as pectin, cellulose, and hemicellulose undergo solubilization, deesterification, and depolymerization during ripening . Cell wall degrading enzymes, such as pectin methylesterase, polygalacturonase, β-galactosidase, endo-1,4-β-d-glucanase, and many others, are involved in this mechanism. Further loss of neutral sugars and galacturonic acid followed by solubilization of the remaining sugar residues and oligosaccharides are also included in cell wall modifications . According to gene expression analysis it has been revealed that ethylene directly regulates the transcription of both a softening-related PpPG gene that encodes an α-L-arabinofuranosidase/β-xylosidase (PpARF/XYL) and an expansin (PpExp3) . In some fruits such as bananas which contain high level of starch in the fruit flesh, enzymatic hydrolysis of starch is a major factor in fruit softening. In citrus fruit, softening is mainly associated with change in turgor pressure, a process associated with the postharvest dehydration and/or loss of dry matter .
Colour development is an important maturity index of many fruits and associated with ripening. In many cases the colour change during fruit ripening is due to the unmasking of preexisting pigments by degradation of chlorophylls and synthesis of anthocyanins and carotenoids . Carotenoid biosynthesis during ripening has been studied using tomato plant as a model. Carotenoids are derived from terpenoids and are synthesized in fruit at a high rate during the transition from chloroplast to chromoplast . Anthocyanins are responsible for orange, red, pink, blue and purple colours in fruits and can be classified in to two groups as flavonoids and phenolic compounds . They are synthesized in the cytosol and localised in vacuoles and synthesized via the phenylpropanoid pathway. Two classes of genes are required for anthocyanin biosynthesis, the structural genes encoding the enzymes that directly participate in the formation of anthocyanins and other flavonoids and the regulatory genes that control the transcription of structural genes . It has been reported that ethylene is involved in regulation of genes related to anthocyanin biosynthesis .
Many fruits emit volatile compounds which are responsible for flavour and aroma of the certain fruit. The metabolism of fatty acids and branched amino acids act as precursors of aroma volatiles in fruit . Aroma and flavour volatile profile of fruits mainly consist mainly of esters, alcohols, aldehydes, ketones, and terpenes. Many studies have been done to explain the association between volatile synthesis and ethylene production. Ethylene treatments can enhance the aroma volatile production in mangoes and honeydew melons . Further showed that aroma production is reduced when ethylene biosynthesis is inhibited by using aminoethoxyvinylglycine (AVG) or 1-methylcyclopropane (1-MCP) indicating that aroma synthesis is correlated with ethylene production and action in fruits.
Astringency which arises due to tannins in fruits shows a decreasing trend during ripening of many fruits. It is reported that astringency depends on the molecular structure of tannin which determines cross linking with proteins and glycoproteins . Therefore tannins give astringent taste when they are dissolved in saliva. An increase in the molecular weight of tannin by polymerization which occurs during ripening causes a lack of astringency due to the insolubility of tannins .
3. Introduction to Banana
Banana (Musa spp.) is one of the most widely cultivated and widely consumed fruit crops in the world. It is said to be as one of the earliest fruit crops which is cultivated at the beginning of the civilization. Bananas are native to South East Asia and it is cultivated in over 130 countries throughout the tropical and subtropical regions of the world . It is recorded as the fourth largest food crop of the world after rice, wheat, and maize . The annual world production of bananas is around 114 million metric tons from an area of 5.6 million ha (FAO 2018). From this total banana production about 50% is consumed in cooked form which is often term plantains while the rest is dessert types . Brazil, India, and Philippines are the principal countries in terms of production of bananas.
Bananas grow in a large range of environments and can produce food all year round. In Sri Lanka, nearly 60,000 ha (20,000ha and 40,000ha in wet zone and dry and intermediate zones respectively) of land is under banana cultivation. It covers about 54% of the total fruit lands. 13,000ha is used to cultivate plantain (for curries) and other 47,000ha is used to cultivate dessert type . There were twenty-nine banana cultivars and two wild species in Sri Lanka . According to a case study in Sri Lankan crop sector currently there are 55 local cultivars in Sri Lanka. Some plantain types of bananas identified in Sri Lanka include Alukesel (ABB), Mondan (ABB), ElaMondan, Atamuru, and Kithala. The most popular dessert type bananas in Sri Lanka are Embul or Ambul (Mysore AAB), kolikuttu (Silk AAB), Anamalu (Gros Michel AAA), Binkehel (Dwarf AAA), Rathambala (AAA), and Ambon (AAA) . According to the Department of Agriculture, many banana varieties grow freely all over Sri Lanka, all year round. They are cultivated in large, medium, and small-scale orchards, and in home gardens. According to Agricultural statistics in Sri Lanka, 2015, the total production of banana is nearly 530, 124 MT annually.
4. Induced Ripening of Bananas
Fruit ripening is a combination of physiological, biochemical, and molecular processes leading to changes in pigments, sugar content, acid content, flavour, aroma, texture, etc. Since banana is a climacteric fruit it is usually harvested at the preclimacteric stage and for commercial purposes artificially ripened. Artificial ripening enables traders to minimize losses during transportations as well to timely release the product at desired ripening stage. Bananas can be artificially ripened using different ripening agents.
4.1. Ethylene Gas
The most popular method practiced in developed countries is application of ethylene gas in ripening rooms. Modern banana ripening rooms are designed with techniques to control temperature, humidity, and ethylene gas concentration and they are equipped with proper ventilation and exhausting systems. Banana combs are properly packed and kept in these rooms and then ethylene is supplied at proper temperature and humidity. Mostly “catalytic generators” are used to generate ethylene in commercial ripening rooms. The concentration of ethylene required for different commodities to enhance ripening is different.
However early in the banana history many researchers tested ethylene as an induced ripening agent. Von Loesecke commented that some scientists showed that ripening of bananas can be induced by exposing them to vapour of apples, which was confirmed when it was shown that ripening of bananas can be accelerated using the vapour that had previously passed through ripe bananas. Finally, it was concluded that exogenous ethylene treatment can induce ripening of bananas with increased rate of respiration and increased level of endogenous ethylene . Burg and Burg reported that low ethylene concentration as 0.1ppm is effective in accelerating the ripening of bananas. Dominguez and Vendrell showed that exogenous ethylene, 100ppm treatment for 12 hours, can immediately increase the endogenous ethylene and CO2 production similar to respiratory climacteric. Further this study showed that increment in respiration depends on time of treatment whereas 12-hour treatment was slightly effective than 6 hours treatment. Lohani noted 11-fold decrease in fruit firmness which occurred within two days after exogenous ethylene treatment. Further it was recorded that ethylene treatment regulated up the activity of four cell wall hydrolases, pectin methyl esterase, polygalacturonase, pectate lyase, and cellulose in “Dwarf Cavendish” bananas.
Calcium carbide when hydrolysed produces acetylene which is an ethylene analogue. Mostly in developing countries including Sri Lanka, calcium carbide is widely used for artificial ripening of bananas, though it is prohibited by the government regulations. Hartshorn conducted a series of experiments to identify effects of acetylene on ripening process of bananas. It was shown in this study that acetylene emits from calcium carbide can enhance banana ripening as treated fruits were uniformly yellow with good flavour, medium starch content, and comparatively soft texture after 120 hours while control samples were remain unripe after same period of time. According to Burg and Burg acetylene has a lower biological activity than ethylene and it was reported in this study that concentration of acetylene should be 2.8 ml/L to enhance ripening of bananas. However Thompson and Seymour reported that bananas do not respond to acetylene at 0.01ml/L while the treatment with acetylene in 1 ml/L led to indistinguishable colour and soluble solids content compared to those ripened by exposure to ethylene at same concentration. Further it was shown in this study that there is no significant difference in sensory attributes between bananas treated with ethylene and acetylene at 1ml/L when they are compared at same stage of ripeness.
However, calcium carbide is not generally recognized as safe and prohibited in Sri Lanka as in most countries under Section 26 of the food (labelling and miscellaneous) regulation of 1993. Calcium carbide is considered as hazardous due to several reasons. Commercial calcium carbide contains traces of arsenic and phosphorous hydride and acetylene emitted from commercial calcium may also contain up to 3 ppm arsenic and up to 95 ppm phosphorous hydride . Arsenic and phosphorous hydride can be poisonous to humans and cause vomiting, diarrhoea with or without blood, burning sensation of the chest and abdomen, thirst, weakness, difficulty in swallowing, irritation or burning in the eyes and skin, permanent aye damage, and so on . Exposure to acetylene gas can cause headache, vertigo, dizziness, delirium, seizure, and even coma .
Ethephon (2-chloroethylphosphonic acid), an ethylene releasing compound, is categorized as noncarcinogenic to humans by IARC (International Agency for Research on Cancer). It penetrates into the fruit and decomposes to ethylene and has been shown to hasten ripening of several fruits including bananas, apples, tomatoes, mango, peaches, citrus fruits, and guava . Pendharkar treated bananas with different concentrations of ethephon. Here it was found out that different concentrations of ethephon significantly influence chemical changes during ripening and 1000 ppm was found as the best concentration of ethephon for early ripening. Nair and Singh showed that prestorage treatments of mangoes (Mangifera indica L., cv. Kensington Pride) with ethephon (500 mg/L) for five minutes increased TSS, TSS/acid ratio, and sugars and reduces chilling injury. Adane compared ethephon treatment and traditional kerosene smoke treatment and their effect on ripening of “Cavendish” bananas, where it was shown that ethephon treated fruits demonstrated higher sensory quality. Apart from being used to initiate ripening, ethephon has been recorded as plant growth regulator which can be used to increase fruit size, induce flowering, enhance colour, and induce flower abscission .
It has been reported that health related studies on ethephon has shown that it has hepatotoxic potential. Ethephon is an organophosphorus compound and it has been reported to get rapidly absorbed in the gut. There is a possibility of converting ethephon into ethylene oxide, then to ethanediol and hydroxyethyl-glutathione and mercapturic acid. Further it has been studied that it can inhibit the growth Streptomyces and their antibiotic production
4.4. Other Ripening Agents
Ethylene glycol is C2H6O2 and commonly used as a coolant and antifreeze. Goonatilake experiments on the effectiveness of ethylene glycol as a fruit ripening agent have reported that when diluted with water, various fruits will ripen faster in colder climactic conditions. According to Stahler and Pont bananas can be artificially ripened by using alkyl alcohol containing between 6 and 14 carbon atoms. Further, it has been reported, in this patent, that lauryl alcohol is preferred to ripen green bananas and treatment with 0.01% by the weight of bananas can change bananas to completely yellow within 48 hours without any loss of palatability.
One of the traditional methods used in Sri Lanka, as well as in many other countries, is smoking. In Sri Lankan traditional practice, bananas are laid in a pit, covered with banana leaves or a sheet cover and smoke, generated from burning of semidried leaves, is directed into the pit. In some countries kerosene burners are used to generate smoke in commercial scale banana ripening. Smoke is known to accelerate ripening due to the presence of acetylene, ethylene, and other unsaturated compounds which can enhance ripening .
Some other ripening agents are ethanol, methanol, propylene, and methyl jasmonate . Ethylene is also emitted from fruit that have already initiated to ripen and can be used to enhance ripening of other fruits. Ethylene production can be stimulated by mechanically wounding the fruit. Here ethylene production is directly proportional to wound dimensions .
5. Effect of Induced Ripening Agents on Quality of Bananas
Lustre compared physicochemical changes occurring during natural ripening and acetylene induced ripening in “Saba” bananas. Here it was shown that acetylene affects the rate of chemical changes during ripening; nevertheless it did not significantly affect the final levels of sugar and starch content in the ripe pulp. Another study which was conducted to examine comparative effect of acetylene and ethylene gas on banana ripening showed that fruits treated with acetylene at 1ml/L exhibited the similar colour score and soluble solids content in fruits treated with ethylene gas. However in this study it was further recorded that sensory quality is the same in the fruits treated with ethylene gas and acetylene gas when compared at same stage of ripeness . Similar research was conducted by Sarananda where effect of acetylene liberated from calcium carbide on ripening of “Embul” (Musa acuminata, AAB) banana. It was clearly exhibited in this study that naturally ripened fruits have excellent sensory quality with flesh colour, flavour, taste, and overall acceptability compared to calcium carbide treated fruits at the stage of fully yellow (Colour Index-6). Nevertheless it was shown that calcium carbide treated fruits achieved the same sensory quality when they were kept for one day more after reaching the fully yellow stage.
According to Adane smoking bananas caused deep yellow colour with black spots on the peel with over softening while ethephon treatment gave uniform yellow colour in the peel at the end of the ripening period. As well Islam et al., 2018, showed that bananas treated with kerosene smoke have significantly low levels of vitamin C. Further in this study it was revealed that calcium carbide treated bananas shows high level of sulphur and trace amount of arsenic and phosphorous.
Gandhi compared natural ripening agents including apple, pear, and tomato with calcium carbide. In this study it was revealed that apple is an effective ripening agent compared to calcium carbide and other tested natural agents and it contributed to the highest sensory acceptability. However calcium carbide treated fruits exhibited the least organoleptic quality compared to naturally ripened and ethephon treated bananas in . Further in this study, the best physicochemical quality attributes such as total sugar, vitamin C, titratable acidity, pH, and total soluble solids were recorded in naturally ripened banana compared to artificially ripened bananas, whereas controversial results were obtained by Kulkarni et al., 2011, which showed that sensory quality and other physicochemical quality attributes were excellent in ethephon (500-1000 ppm) treated bananas compared to naturally ripened fruits at the day of storage. Reference compared ripening techniques such as ethephon, smoking, and keeping in low density polyethylene plastic, in Teff straw, and in banana leaves. The results supported that smoking enhance faster ripening but led to least marketability, 28.67% at day of storage when other treatments reported more than 83% of marketability. The reduction of marketability of smoked bananas was due to blackening and over softening.
Effect of induced ripening agents including calcium carbide, potash, and leaves of Irvingia gabonensis and Jatropha curcas leaves on nutritional and mineral composition of bananas was studied by Sogo-Temi et al. . They reported that the chemical ripening agents tested contributed to lower levels of protein compared to biological ripening agents. Also levels of Pb, Cu, Zn, and Mn were higher in calcium carbide treated fruits than other ripening agents.
Hakim found that nutritional value of ethephon treated bananas is less than untreated samples where ascorbic acid content, β-carotene content, and mineral content were less in quantities.
Reference compared aroma compounds in naturally ripened and ethylene treated ripened banana (Musa acuminata). According to the data obtained by this study total aromatic concentration was higher in naturally ripened bananas (60 437 μg/kg) compared to that (55,243 μg/kg) of ethylene treated bananas. Most of ester compounds including n-butyl acetate, isopentyl isobutanoate, 2-pentyl formate, 2-cyclohexanol acetate, ethyl isobutanoate, and 2-pentenyl butanoate were detected in significantly higher levels in naturally ripened bananas compared to ethylene treated samples. The same study showed that there was a significant difference in sucrose level as it was 98.40 g/kg in naturally ripened banana and 89.40 g/kg in ethylene treated bananas. As well total polyphenols content were reported as significantly different in the two types where naturally ripened bananas had 24.90 GAE, mg/L while ethylene treated bananas had 25.10 GAE, mg/L level of total polyphenols.
The banana ripening process can be enhanced using artificial ripening agents such as ethylene gas, ethephon, acetylene (emitted from calcium carbide), ethylene glycol, and alkyl alcohols (containing 6-14 carbon atoms such as lauryl alcohol). Smoke generated from burning green leaves or kerosene burners are also used as traditional methods in banana ripening. Many studies on the effect of different ripening agents on fruit quality appear to show that naturally ripened bananas exhibit better sensory characteristics compared to treated fruits.
The numerical data supporting this review article are from previously reported studies and data sets, which have been cited, and are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that there are no conflicts of interest regarding the publication of this paper.
Ethene (ethylene) is the most important organic chemical, by tonnage, that is manufactured. It is the building block for a vast range of chemicals from plastics to antifreeze solutions and solvents.
Figure 1 On the site at Grangemouth in Scotland, ethene is produced by steam cracking of naphtha.
By kind permission of INEOS Manufacturing Scotland.
Uses of ethene (ethylene)
The principal uses of ethene are to produce:
- ethylbenzene and hence phenylethene and poly(phenylethene)
- chloroethene (vinyl chloride) and hence poly(chloroethene), i.e. poly(vinylchloride), PVC
- ethylbenzene and hence phenylethene and poly(phenylethene) polystyrene
b) other chemicals
- epoxyethane and hence the diols, such as ethane-1,2-diol
The manufacture of polymers is the main use of ethene. Poly(ethene) accounts for about 60% of the world demand for ethene (HDPE 28%, LLDPE 18%, LDPE 14%), while dichloro-1,2-ethane, the precursor for chloroethene and thence PVC, accounts for a further 11%. Ethylbenzene, the route to poly(phenylethene), uses another 5%1.
About 16% of ethene is used worldwide to make epoxyethane (ethylene oxide).
Annual production of ethene (ethylene)
|World||134 million tonnes1|
|Asia Pacific||50 million tonnes1|
|U.S.||25 million tonnes2|
|Europe||20 million tonnes3|
|Middle East||20 million tonnes1|
1. Calculated from data, Nexant and ChemVision. Estimated data for 2014
2. 2015 Guide to the Business of Chemistry, American Chemistry Council 2016. Data for 2014
3. Petrochemicals Europe 2016. Data for 2015
Much of the ethene produced in the Middle East comes from Saudi Arabia, 17 million tonnes a year, with one refinery producing over 2 million tonnes a year, the 4th largest ethene production plant in the world.
Manufacture of ethene (ethylene)
Ethene is produced from the cracking of fractions obtained from distillation of natural gas and oil.
The processes are:
a)the steam cracking of ethane and propane (from natural gas and from crude oil)
b) the steam cracking of naphtha from crude oil
c) the catalytic cracking of gas oil from crude oil. The choice of feedstock depends on availability, price
(which can vary considerably), and what other products from cracking are needed.
The vast majority of ethene is produced by steam cracking. Some crackers are capable of producing 3 600 tonnes of ethene a day.
Figure 2 Distribution of ethene by pipeline across Europe.
Within Europe, the ethene that is not needed at the site at which it is produced is fed into pipelines which connect other chemical plants and refineries (Figure 2).
A new wave of crackers is being built in the United States to take advantage of a large supply of ethane and other hydrocarbon gases from fracking. The US produces about 25 million tonnes of ethene a year. In 2010, about 9 million tonnes came from ethane and another 4 million from propane. By 2015 the amount from ethane had increased to 10 million tonnes and by 2020 it is expected to rise to about 140 million tonnes from ethane and 50 from propane, a direct result of the growth in fracking. In 2016 the first shipments of ethene from fracking fields in the US were being processed in refinmeries in Europe.
Figure 3 The first shipment of ethane from shale gas from the US to Europe, was delivered to the petrochemical plant at Rafnes in Norway in March 2016 and the first to Grangemouth in Scotland the following September. The first shipments of propane will be delivered in 2017. The ethane, which has been stored at 283K, is used as a fuel and is also cracked to produce ethene and other alkenes. Using propane as the feedstock, a higher proportion of propene is obtained. The Dragon, photographed here, is the largest gas tanker in the world, holding 27,500 m3 of gas.
With kind permission of Ineos
New plants based on bioethanol produced from sugar cane are in operation and are also being constructed in Brazil. High yields of bio-based ethene are obtained by dehydrating ethanol vapour using a catalyst containing a mixture of magnesium oxide, alumina and silica at 600-750 K:
The ethene is used principally to produce bio-based poly(ethene).
Date last amended: 4th January 2017
Apples are a fruit we tend to take for granted. With so many great varieties to choose from, how could we ever tire of them? They bear a host of fascinating names, like Jonagold, Granny Smith, Elstar and Pink Lady. They sport a rich variety of hues – some green, some red, some brightly mixed. It’s no surprise that the apple is the most popular fruit, way ahead of its delicious fruity rivals such as bananas, oranges and mandarins. In this post we’ll mention a few things about apple nutrition and explain to you what apples have to do with the gas, ethylene!
Apples produce a gas called ethylene on ripening. People are often shocked to hear this as it does sound somewhat mysterious and unappetizing but have no fear; ethylene is a natural plant hormone that sets off the ripening process. And, amazingly, any other fruits that are stored in close proximity to apples will ripen more quickly! You need to pay attention to this: if your fruits ripen faster they will subsequently tend to spoil sooner. Apples aren’t the only fruits that emit ethylene in this manner – apricots, pears and bananas also produce this plant hormone, as do some vegetables e.g. potatoes.
Many fruits and vegetables wouldn’t ripen without ethylene
Bananas have to travel a long distance before they arrive on our supermarket shelves. They are harvested whilst they are still green so that molds will not affect them during transit. After shipment, before they reach the shops, they are then artificially ripened by exposure to ethylene, which also promotes a more appetizing appearance. This is how our shop-bought bananas acquire their customary yellow color and how our tomatoes become a beautiful glowing red – in their unripened state, neither tend to sell very well.
How to take advantage of this ripening effect
You can use the positive ripening effects of ethylene yourself. At room temperature, place your unripe fruit or vegetables in a sealed container or bag together with an apple (or other ethylene-producing fruit or vegetable). This will accelerate the natural ripening process. Don’t worry that you’ll then have to eat all your ripened fruit and vegetables in a hurry, before they spoil; simply store them in a Liebherr BioFresh compartment. Despite having hastened the ripening process, you will still have plenty of time to enjoy your fruit and veggies at your leisure. You can find out all about storage lives and about which fruits/vegetables are best suited to BioFresh storage by referring to our BioFresh storage data or by downloading our BioFresh app. And, should you find that the ripening process has advanced a little too far, and that your apples are looking a little worse for wear, do not despair – they will still be absolutely perfect for making a great applesauce!
Apples need to be stored in a cool, dry place and can be kept for up to 50 days in a refrigerator. In a Liebherr BioFresh compartment they can be stored for up to 80 days. But, when storing apples, there is one, not-so-insignificant thing that you need to be aware of: Apples produce a gas called ethylene, a natural plant hormone that sets off the ripening process. And, amazingly, any other fruits that are stored in close proximity to apples will ripen more quickly!
Apples contain hardly any protein or fat, and so the energy they deliver comes more-or-less exclusively from carbohydrates. A medium-sized apple (100 g) has about 50 kcal, which corresponds to about 2% of the daily energy requirements for a predominantly sedentary adult, making the apple an ideal snack for in-between meals. Thanks to its mix of easily digestible sugars, in the form of fructose and glucose, an apple readily staves off dips in energy levels between main meals.
Ask an expert: Why do bananas ripen fruit?
A reader question delves into the secret life of fruit hormones. By AG STAFF • November 7, 2013 • Reading Time: < 1 Sharing Post Tags ask an expertfoodfruitsreader question Why do bananas ripen other fruit? (Photo: Getty Images) Advertisement
QUESTION: Why do bananas ripen other fruit?
Andrew Burns, Surry Hills, NSW
Dr Mala Gamage, CSIRO food scientist, says:
As they ripen, bananas, apples, kiwi fruit, tomatoes, figs, pears and some other fruits release a gaseous plant hormone known as ethylene. These ‘climacteric’ fruit, as they are called, will respond to ethylene in their environment and begin the ripening process. As they do so, they ripen other fruit (and perish flowers) around them.
Bananas are medium-level producers of ethylene compared with kiwi fruit, for example, which produce more. But because bananas are large, and often you’ll have a bunch of them in your fruit bowl, they can appear to be the cause of other fruits ripening.
Ethylene gas is also used commercially to ripen bananas.
If you have a question for an expert, email it to [email protected]
Fruit ripening and storage
Fruit that continues to ripen..
Climacteric fruits continue to ripen after being picked due to a process accelerated by a gaseous plant hormone called ethylene. Bananas, apples, kiwi fruit, figs, pears, mangoes, peaches, plums, tomatoes, avocadoes and some other fruits respond to ethylene in their environment and begin the ripening process.
Non-climacteric fruit produce little or no ethylene gas and therefore do not ripen once picked; these fruits include citrus fruits, raspberries, blueberries, strawberries, watermelons, cherries, grapes and grapefruit.
Bananas are very sensitive fruits – they react quickly to extreme temperatures! Green bananas, or any unripe fruit for that matter, is a test of faith. You assume that they’ll soon turn yellow and be ripe enough to eat. …
Ripening fruit gives off ethylene gas, and putting the fruit in a paper bag traps the gas near the fruit, causing it to ripen faster. Place bananas in a brown paper bag and close loosely. Ethylene will build up and circulate within the bag, speeding up the ripening process. Check now and again so you can take them out at your desired ripeness. This usually takes about 3 days depending on room temperature. To ripen the bananas faster, place a ripe fruit such as an apple or tomato in the bag as well.
If you store bananas in the fridge they will turn black! However the flesh inside will remain good to eat – they just don’t look too nice! Remember to only refrigerate bananas once they are ripe. Occasionally this discolouration can happen to our bananas on very cold delivery days, although we do our utmost to keep them warm by wrapping them in blankets – exposure to extreme cold even for a short period, may turn the bananas dark grey in colour.
To keep a bunch of bananas fresh for longer, wrap the stems in some plastic wrap. Re-cover the bananas with the wrap after removing one. This method prevents ethylene gas, produced naturally in the ripening process, from reaching other parts of the fruit and prematurely ripening it.
This Is the Secret to Storing Every Type of Fruit and Vegetable So They Last Longer
Fact: The United States throws away 150,000 tons of food daily. And on average, around $1,500 worth of food is wasted per year in each household. Out of everything edible we waste, fruits and vegetables account for 39 percent of America’s total.
The good news is that a few simple tricks could have a massive impact on the environment (and on our grocery expenses) to reduce the amount of fresh produce we toss every day.
Step one in wasting less produce is remembering that storing fruits and vegetables too closely together is a common mistake that can lead to food going bad. Build-up of the chemical compound ethylene gas will cause them to go off, so apples, melons, apricots, bananas, tomatoes, avocados, peaches, pears, nectarines, plums, figs, and other fruits and vegetables should be kept separate as these produce the most ethylene.
RELATED: We Put 3 Hacks for Ripening Fruit Faster to the Test—Here’s What Worked
The experts at Space Station helped us pull together this handy guide for storing fresh foods smarter—because the longer your produce, meat, and more lasts, the less you trash and repurchase.
Netting for lemons, oranges, and limes is very dangerous to sea life and birds, so these types of fruits should always be bought loose. You can keep them out at room temperature, but once citrus fruits are past peak ripeness, storing them in the fridge will help them last longer (same goes for tomatoes and avocados). If your citrus starts to turn, you can slice the fruit up and freeze it: frozen citrus is great as ice cubes for drinks.
RELATED: The Major Mistake You’re Making With Citrus Fruits—Plus How to Buy and Store Them
Wash and dry loose leafy salad greens in a salad spinner, then wrap them loosely in paper towels and store in a food storage container to keep the leaves from going soggy.
Onions and Potatoes
Onions, potatoes, and shallots should be stored in a cool dark place to keep them fresh, like a basket in a cupboard or a cellar. Avoid storing these products in plastic bags as this encourages spoilage. Once cut, onions should be stored in a resealable bag in the fridge where they will last for around a week or stored in a container and kept in the freezer.
Wash cucumbers as soon as you bring them home from the grocery store. Make sure they’re thoroughly dry as excess water will spoil them, then wrap each in a cloth or towel to prevent sogginess. Store in the fridge in a reusable vegetable bag.
Apples and Bananas
If you won’t be eating them immediately, buy bananas when they’re still slightly green and store them away from other fruits in the fruit bowl (they release high amounts of ethylene gas, which as mentioned can cause other fruits to go off more quickly). Consider using a banana tree to keep them separated and minimize bruising. Keep apples in an uncovered fruit bowl on the countertop and make sure to store them out of direct sunlight.
A great hack for storing fresh basil and herbs is to chop the leaves in a food processor and place into an ice cube tray with a little olive oil and store in the freezer. When basil is needed for a dish, just pop in a ready-made ice cube.
Meat and Fish
Storing meat and fish in containers in the freezer will save money and food waste. Keep them well-organized (first in, first out) with labels that clearly state the date the items were frozen, as frozen meat should be eaten within three to six months.
RELATED: How to Store Fruits and Vegetables
Control of Ethylene in fruits & vegetables warehouses and cold stores
This article explains the repercussions of having high concentrations of ethylene in warehouses and cold stores. Industries that are involved in handling and storage of fruits and vegetables are severely affected monetarily by Ethylene. High concentration of ethylene causes premature aging and rotting of fruits and vegetables and wilting of flowers and leafy vegetables – thus lowering its shelf life…
Conventional methods (adopted by most warehouses and cold stores) of lowering temperature and humidity and using gases like nitrogen and sulphur increase the shelf life but have several disadvantages viz-a-via changing the natural properties of fruits and vegetables. Refrigeration and humidity control even small amount of ethylene gas during storage is enough to hasten the process of decay of fresh produce. This makes ethylene control absolutely necessary in the cold chain.
slows the decay but is not enough to halt the production of ethylene gas in cold stores and warehouses.
Thus the most practical solution is ethylene control and removal in the cold chain. Ethylene removal is a natural process that does not affect the properties of fruit. This article discusses at length how ethylene control through adsorption and chemisorption can ensure that fruits and vegetables retain its “naturalness”. These can be ripened as per demand without bearing traces of toxic gases.
Ethylene – The Ripening Hormone
Ethylene gas (C2H4) is an odorless, colorless gas that exists in nature and which is triggered at maturity in climacteric fruits. . Ethylene, also known as the ‘death or ripening hormone’ plays a regulatory role in many processes of plant growth, development and eventually death.
Fruits are either ethylene producers or absorbers. Apples, bananas, melons, pears and peaches are ethylene producers. Tomatoes are moderate ethylene producers. Broccoli, cabbage, cauliflower, etc., are ethylene sensitive.
So, by the rule of the thumb it is preferable to avoid storing ethylene producing fruits with ethylene absorbing ones. Ventilating the storage area also serves the purpose but just to an extent.
Apples are ethylene producers while cauliflower is ethylene sensitive.
Cold Storage are classified in the following 3 categories:
- Cold storage for storage of fresh horticulture product which does not require pre-cooling
- Multi-commodity cold storage for short term and long term storage of fresh horticulture products, which require pre-cooling and varying storage
- Control Atmosphere storage (CA)
Ethylene Generation & Sensitivity Chart for Some Common Fruits and Vegetables
VH = very high; H = high; M = medium; L = low; VL = very low
Perishable Commodities (Fruits & Vegetables)
|Ethylene Generation||Ethylene Sensitivity|
The Ethylene Effect
The overall effect of Ethylene is to hasten ripening, aging and eventually spoilage.
Some bad effects of ethylene on some common fruits and vegetables are:
- Apples: scald
- Eggplant: brown spots
- Bananas: decay
- Potatoes: sprouting
- Grapes: mold Onions/ garlic: odor
- Broccoli: yellowing
- Carrots: bitterness
- Carnations: sleepiness
- Green leafy vegetables: loss of color
Presence of ethylene in amounts ranging from a few parts per billion (ppb) to a few parts per million (ppm) can reduce plant vigour, decrease life of various plant parts and reduce stock quality.
0.1 ppm is commonly considered the threshold level for ethylene action on plants.
Conventional Practices are Harmful for Fruits and Vegetables
Any closed environment, such as truck trailer, shipping container, warehouses and cold rooms, will have a similar effect resulting in increased concentration of Ethylene.
At the latter part of post-harvest, artificial ripening by using ethylene is general practice as it ensures that the produce reaches the consumers (retail outlets) with a degree of ripeness, which brings out its best in terms of taste, color, texture and nutritional value. One of the most common examples is the ‘forced’ ripening of bananas during high demand periods.
However these conventional methods adopted by most warehouses and cold stores of lowering the temperature and humidity and using gases like nitrogen and sulphur increase the shelf life but have several disadvantages.
- It uses toxic gases
- It is dangerous for human health
- It changes the natural properties of fruit as well
Refrigeration and humidity control slows decay but is not enough to halt the production of ethylene gas in cold stores and warehouse. Even small amount of ethylene gas during storage is enough to hasten the process of decay of fresh produce. This makes ethylene control absolutely necessary in the cold chain.
Why Ethylene Control!!!
Advantage of Ethylene Control
- Extends the life cycle of the fruit/ vegetable after plucking
- Warehouse owners can easily preserve freshness and reduces spoilage of fruits and vegetables
- They are able to meet increasing demands of non-seasonal fruits and vegetables
The three main application areas are:
- controlled atmosphere storage
- fruit/vegetables ripening rooms
- shipping / transportation of the horticultural produce
These are described briefly in the following.
Controlled Atmosphere Storage (CA) – The concept of controlled atmosphere (CA) storage of horticultural products is based on the control of two major factors affecting plant aging
- reduction of respiration rates during
- delay of ethylene-triggered changes leading to senescence.
CA storage involves the use of:
- increased levels of carbon dioxide (CO2)
- decreased levels of oxygen (O2) in the atmosphere
- low storage temperatures and lastly
- preventing of the buildup of internally-generated ethylene to threshold levels which could trigger changes leading to senescence and death
Controlling ethylene gas will maintain the quality and extend the life of horticultural products, allowing them to be stored for a much longer period of time. While refrigeration and humidity control will slow ripening and decay, they will not halt ethylene control.
Ripening Rooms – The general practice is picking Fruits and vegetables when it is “green” so that there is ample time between harvesting and distribution. The “green” produce is allowed to ripen – some naturally, but much is helped along by exposure to elevated levels of ethylene. However it is necessary to ensure the following:
- Ripening rooms in buildings separate from traditional cold storage buildings or CA storage
- If the ripening room must be located in the storage area, several precautions should be taken:
- Ethylene should by vented from the ripening room to the outside after the exposure period is
- Exhaust fans (capable of moving 6 to 8 room volumes per hr.) will allow ethylene level to be reduced to approximately 1% of the
However because of temperature and humidity concerns, makeup (dilution) air is typically drawn from the refrigerated area surrounding the ripening room. Even after venting, the ethylene levels may still be high enough to continue the ripening process and cause damage to product. Thus a “re-circulating air scrubber (Air & Gas Purification System)”, with a special media should be employed to reduce the ethylene concentration below threshold levels.
Shipping of Produce – Even small amounts of ethylene gas during shipping and storage causes fresh produce to deteriorate faster.
Controlling ethylene levels preserves freshness
The latest technology from Bry-Air, EcoScrub Air & Gas Purification System extends shelf life, minimizes loss due to decay, ensures off season availability and eliminates harmful preservation practices that use Nitrogen and Sulphur gas. Fruits and vegetables retain their “naturalness: These can be ripened as per demand without bearing traces of toxic gases.
Fruits & Vegetables Producing Ethylene Or Sensitive To Ethylene
We all know that one bad fruit in the box spoils the whole box of fruits. Only one apple, banana, kiwifruit, mango or guava can spoil the other fruits placed nearby. Why it is so? What causes fruits and vegetables to rot? The reason is the ethylene gas released by fruits and vegetables which is a ripening gas. It should be noted that the ethylene gas is used to ripen raw fruits. You should know what fruits and vegetables emit ethylene gas, and which give off most.
Find a list of fruits and vegetables that produce ethylene gas and the foods which are sensitive to ethylene.
Ethylene Producing Fruits
Fruits Ripening Gas – Ethylene
The natural question is what is ethylene gas, how it is used and is it safe for humans. Ethylene is a hydrocarbon gas (C2H4, molecular weight 28.05), flammable, odorless, harmless and tasteless . It is a type of plant hormone, known as senescence hormone released by fruits and vegetables. In the plant, it is produced by the aging tissues and nodes of stems. It is obtained from petroleum and natural gas.
Effect of Ethylene on Fruit Ripening?
You may be interested to know how does the presence of ethylene affect fruit ripening. The effect of ethylene (senescence hormone) is to promote ripening of fruits to make them softer and sweeter. The ethylene, therefore, is a natural ripening agent. Ethylene is a plant hormone resulting from metabolism, whose role is to ripen the fruits. It should be noted that if you do not monitor ripening carefully, your fruit may rot as the quicker ripening is actually a form of accelerated aging that will decrease the product quality and shelf life.
In some countries, growers use calcium carbide for ripening fruit. The calcium carbide produces acetylene gas when it comes in contact with moisture. The acetylene gas is also a ripening agent similar to ethylene gas.
Following are the effects of ethylene gas on the fruits and vegetables:
- Apples lose crunchiness
- Fresh produce and flower decay, wilt
- Leafy vegetables and eggplants spotting
- Yellowing of cucumbers, broccoli and Brussels sprouts
- Rind of citrus breaks down
e can use this knowledge on ethylene to extend the life of fruits and vegetables and prevent their spoilage.
Both fruits and vegetables release ethylene gas, however, fruits produce more ethylene than vegetables do. While some fruits and vegetables are high ethylene producers, others are more sensitive to it.
Ethylene is used to control the ripening process of fruits by introducing this gas into a controlled environment. When ethylene producing foods are kept in close proximity with ethylene-sensitive foods, the gas will speed up the ripening process of the other produce.
How To Prevent Food Spoilage
So you can speed up the ripening process of an unripe fruit by putting an ethylene producing food near to it, for example, by putting an unripe avocado with an apple in a bag.
- The action of ethylene slows down at lower temperatures, so the fruit does not respond well to externally supplied ethylene. that is why you can store your fruits in fridge to slow down their ripening process.
- Some fruits and vegetables are sensitive to the ethylene gas, so keep such produce away from ethylene producers as they deteriorate quickly and decay prematurely in high- ethylene environment. The degree of damage depends upon the concentration of ethylene, the temperature and duration of exposure .
- High ethylene producing fruits should be kept away from other fruits and vegetables. Store fruits and vegetables separately, because fruits release more ethylene gas than vegetables, which can spoil the veggies. Keep leafy vegetables and lettuce away from fruits. Therefore, store ethylene emitting produce such as apples, avocados, bananas, melons, peaches, pears, tomatoes, etc. separately from broccoli, cabbage, cauliflower, leafy greens, lettuce, etc. as these are ethylene sensitive.
- Do not store spinach, kale or similar leafy vegetables near apples, bananas or peaches, otherwise they will turn yellow quickly and limp .
- Keep away your ripe foods from ethylene-producing foods to last longer.
- Storing potatoes with apples naturally inhibit sprouting in potatoes. The potato industry introduce trace amounts of ethylene into potato storage boxes to delay the sprouting process significantly .
- Keep Onions & Potatoes Separated as both can release moisture that will cause each other to spoil faster. Store them separately in a dry, cool and airy place. Many people have given ethylene as the reason for storing onions and potatoes separately, but that is not true; both potatoes and onions do not produce ethylene gas, only potato is sensitive to this gas .
- Remove and discard the older rotten fruits so that your other fruits and vegetables last longer with full nutritional benefits.
- Citrus fruits do not ripen further after they are picked so they have long self-life.
- Note that tomatoes are not artificially reddened by ethylene. The normal tomato ripening process can be accelerated by externally applied ethylene .
Ethylene Producing and Ethylene Sensitive Fruits & Vegetables
The following chart gives a list of foods which are high emitters of ethylene and foods that are sensitive to ethylene. Looking at the list of foods, you can make an intelligent combination of produce for storing them without spoilage.
Ethylene Producing Fruits & Vegetables
|Fruits & Vegetables|| Ethylene
|Avocados, unripe||Low||Yes, Very|
|Kiwi, unripe||Low||Yes, Very|
|Melons, Honey Dew||Medium||Yes|
NO Ethylene Emission, Not Sensitive
|Fruits & Vegetables|| Ethylene
Ethylene Sensitive Fruits & Vegetables
|Fruits & Vegetables|| Ethylene
|Avocados, unripe||Low||Yes, Very|
Fruits & Vegetables That Produce Ethylene
Some fruits and vegetables emit more ethylene at a much higher rate than others. The question is which foods emit the ethylene gas most?
Apples, Apricots, ripe Avocados, Cantaloupe, Guavas, Mangoes, Nectarines, Papayas, Peaches, Pears, Plums, Prunes, Quinces and ripe Tomatoes are high to medium ethylene producing fruits; while Berries (Blackberries, Blueberries, Cherries, Raspberries, Strawberries), Cucumbers, Figs, Grapefruit, Grapes, Lemons, Limes, Lychees, Okra, Oranges, Pineapples and Tangerines produce only a small amount of ethylene gas.
The following fruits and vegetables are ethylene emitting fruits and they themselves are sensitive to it.
Apples, Apricot, Avocado (ripe & unripe), Bananas (green), Cantaloupe, Cucumber, Fig, Grapes, Guava, Kiwi, (ripe & unripe), Mango, Honey Dew Melon, Okra, Papaya, Peach, Pear, Plum, Prune, Quince, Tomato (Green) produce ethylene and they are sensitive to ethylene gas.
Fruits & Vegetables Sensitive To Ethylene
The following fruits and vegetables are highly sensitive to ethylene gas, but they themselves do not emit ethylene.
Asparagus, Basil, Beets, Bok Choy, Broccoli, Brussels Sprouts, Cabbage, Chinese, Cabbage, early, Carrots, bunched, Cauliflower, Celery, Eggplant, Elderberries, Green Beans, Green Peas, Herbs, Leeks, Lettuce, Mushrooms, Parsnips, Peppers, hot chili, Persimmons, Pomegranates, Potatoes, Pumpkins, Radishes, spring, Rutabagas, Salad Mixes, Sprouts, Squashes, summer, Squashes, winter, Sweet Potatoes, Turnips, Watermelon, etc.do not produce ethylene but they are highly sensitive to it.
Fruits & Vegetables that DO NOT Produce Ethylene Gas
Artichokes, Cherries sweet, Chicory, Coconuts, Corn, sweet, Cranberries, Garlic, Ginger, Kohlrabi, Onions, Peppers sweet, Pomegranates, Rhubarb, etc. do not emit ethylene and are not sensitive to it.
Oranges produce very small amount of ethylene gas and are not sensitive to this gas.
How to tell if the mango is ripe?
1. Lelièvre, et al., Ethylene and fruit ripening,pdf
2. Ethylene – Wikipedia, the free encyclopedia
3. Curry, E.A. and M.E. Patterson. 1993. Controlling ethylene biosynthesis with natural compounds. Proc. Wash. State Hort. Soc.: 312-313.
4. Spoiled Rotten—How to Store Fruits and Vegetables,
5. Bob Mueller, Using Ethylne, Potato Grower Magazine, August 2013 Issue Published online: Aug 04, 2013.
6. Engineering ToolBox! Fruits and Vegetables – Optimal Storage Conditions, www.engineeringtoolbox.com/fruits-vegetables-storage-conditions-d_710.html
7. California Fresh Market Advisory Board, Informational Bulletin No. 12, June 1, 1976.
mohan1948 October 16, 2016 7:06 PM Thanks a lot. Well researched and extensive. Content of your article far exceeds the matter I have been gathering from various sources during the last ten years. Kudos and keep it up. P. Mehta October 17, 2016 7:13 AM Thanks for your comments and appreciation. Joe Smith May 12, 2017 9:33 AM Is it ok to store squash next to onions? P. Mehta May 12, 2017 11:03 AM High humidity is the worst enemy for squash, so storing squash with onions can damage squash due to the release of moisture from onions. Unknown May 13, 2017 1:56 PM Thank you for your time and work on very thorough and comprehensive list. Trish September 04, 2017 12:04 AM This page (whole site really) is Great!! I was just hoping for a list of ethylene producing produce, i did not expect to find such a complete reference. Thank you so much!
Ethylene is an important, natural plant hormone.
It regulates the ripening and senescence (aging) of plants. Ethylene is normally produced in small quantities by most fruits and vegetables. However, climacteric fruits, like bananas, avocados and tomatoes create larger amounts of ethylene and this release of ethylene starts several actions like increased respiration, more ethylene production, and changes in color, aroma, and flavor. Fortunately, the onset of this internal ethylene production can be controlled. The ability of fresh produce companies and distribution centers to apply ethylene allows the promotion of predicable ripening times and more uniform ripening…the result is better quality and consumer eating experience.
Ethylene is Generally Recognized as Safe (GRAS)
by the United States Food and Drug Administration (FDA). Given the numerous amounts of food substances, the FDA does not categorize every one. Salt, pepper and vinegar are examples. These, along with ethylene, all are within the category of food substances that, when used for the purposes indicated, in accordance with good manufacturing practice, are regarded by the FDA as generally recognized as safe (GRAS) for such uses.
Calcium Carbide is NOT safe for ripening.
Calcium Carbide is used in some countries as source of acetylene gas, which is an artificial ripening agent. However, acetylene is not nearly as effective for ripening as is ethylene, and acetylene is not a natural plant hormone like ethylene. Also, calcium carbide may contain traces of arsenic and phosphorus, both highly toxic to humans, and so the use of this chemical for ripening is dangerous and illegal in most countries.
Ethylene has been found not harmful or toxic to humans in the concentrations found in ripening rooms (100-150 ppm).
In fact, ethylene was used medically as a anesthetic in concentrations significantly greater than that found in a ripening room. However, ethylene is often targeted as the reason for difficulty in breathing in ripening rooms; what can affect some people is usually either:
- Carbon Dioxide (CO2,) levels: CO2, is produced by the ripening fruit in the room and levels increase over time, or
- Oxygen levels: The oxygen in the room when loaded is taken in by the ripening fruit. This sometimes will make breathing in a ripening room difficult.
The increased CO2, and decreased oxygen levels are the main reasons for venting the ripening room.
Ethylene action slows at lower temperatures.
At their minimum temperature levels, fruit is basically inactive and does not respond well to externally supplied ethylene.
Ethylene will penetrate most substances.
In fact, it will permeate through produce cardboard shipping boxes, wood and even concrete walls.
Ethylene is harmful to many fruits, vegetables, and floral items.
While ethylene is invaluable due to its ability to initiate the ripening process in several fruits, it can also be very harmful to many fruits, vegetables, flowers, and plants by accelerating the aging process and decreasing the product quality and shelf life. The degree of damage depends upon the concentration of ethylene, length of exposure time, and product temperature. If ethylene damage is suspected, testing for ethylene levels should be performed (here are some ways to test). This will indicate if one of the steps below should be followed:
- Ethylene producing items (such as apples, avocados, bananas, melons, peaches, pears, and tomatoes) should be stored separately from ethylene-sensitive ones (broccoli, cabbage, cauliflower, leafy greens, lettuce, etc.). Also, ethylene is emitted by engines. Propane, diesel, and gasoline powered engines all produce ethylene in amounts large enough to cause damage to the ethylene-sensitive produce items mentioned
- Ventilate the storage area, preferably to the outside of the warehouse, on a continuous or regular basis to purge the air of any ethylene
- Remove ethylene with ethylene absorbing filters. These have been proven in reducing and maintaining low ethylene levels
Ethylene is explosive at high concentrations.
At 27,000 ppm, just a spark can ignite ethylene and cause a deadly explosion. We have an entire section of our web site devoted to the explosions that can result from excessive ethylene: ethylene explosions. However, when using our products as directed, reaching the explosive level is not possible. The explosive level is about 200 times greater than the level necessary to initiate ripening. Always use our generators in ripening rooms that are 1600 ft3 or larger (45 m3).
Ethylene is used to ‘degreen’ citrus.
This is a natural process that triggers pigment changes: the loss of green peel color by removing the chlorophyll, which allows the orange or yellow to fully cover the entire peel. No loss of flavor is caused; this is merely a continuation of the natural plant process.
I hear that ethylene is explosive. How can I be sure that I’m safe from this danger?
Yes, ethylene is very explosive. At concentrations above 27,000 part per million (ppm), just a spark can cause it to explode. There have been several instances of explosions in ripening rooms where cylinders were in use…we have compiled a list of ethylene explosions.
However, the ripening process of most fruits can be initiated by ethylene at concentrations as low as 50 ppm, or less than 1% of the explosive level, and most operators ripen with 1,000 ppm or less. Catalytic Generators are the safest commercial form of ripening; they produce small, controlled amounts of ethylene and when used as directed, they cannot produce explosive amounts of ethylene. That is why so many fresh produce companies use our generators rather than gas cylinders.
When using our generator and Ethy-Gen® II Ripening Concentrate in rooms that are 1,600 ft3 (45 m3) or larger, there is NO CHANCE OF ETHYLENE EXPLOSION. The United Kingdom takes the threat of explosion from cylinders very seriously. The UK’s Health and Safety Executive/Local Authorities Enforcement Liaison Committee (HELA) has posted a circular on their web site explaining that generators are the preferred options for ethylene application and that the “use of cylinders of pure ethylene should be vigorously discouraged.” For more details, please click here.
Is ethylene really necessary for banana ripening? Won’t they ripen on their own?
Bananas are harvested mature but very green in order to survive the trip from the growing regions to destinations across the world. Along with a rise in pulp temperature, an external ethylene application will trigger the proper ripening process to begin, which includes the fruit producing internal ethylene. This natural process results in uniform, controlled and predictable ripening. Without this exposure to external ethylene, bananas will eventually soften, but the change in color will not be uniform and the peel will be dull, pale yellow, and unattractive.
I’m a student…how can I do an experiment with ethylene for ripening? Do you sell your products to end users?
Please see this page for more information: Ethylene / Ripening Experiment
The following are common questions about the use of ethylene gas in the ripening process. The material is reprinted from a fact sheet1 that has been available to the industry for many years.
What is the effect of ethylene on fruit ripening?
Ethylene can promote ripening in tomatoes, bananas, citrus, pineapples, dates, persimmons, pears, apples, melons, mangos, avocados, papayas and jujubes – a clear indication that the action of ethylene is general and widespread amongst a number of fruits. It is clear that ethylene is a ripening hormone – a chemical substance produced by fruits with the specific biological phenomenon of accelerating the normal process of fruit maturation and senescence.
What do you mean ‘promote’ the ripening process?
Using tomatoes as an example, the life of a tomato fruit begins with fertilization of the flower ovules. After fertilization, the young fruit goes through a short period of cell division which is then followed by a rapid period of growth as these cells enlarge. During the final stages of growth and development, the tomato fruit reaches its full size and is now mature. This period of growth and development, from fertilization to development of the mature fruit, requires about 45-55 days, depending on the cultivar and the season. During the growth and development period, there are many chemical and physical changes occurring that have an impact on fruit quality and ripening behavior after harvest. Ripening is the final stage of the maturation process when the fruit changes color, and develops the flavor, texture and aroma that makes up what we define as optimum eating quality. The biological agent that initiates this ripening process after the fruit is mature is naturally produced ethylene – this simple plant hormone described and understood over 40 years ago. While there are other factors involved in this “triggering” of the ripening process by ethylene, it is essentially a universal ripening hormone. When this internal concentration of naturally produced ethylene increases to about 0.1 – 1.0 ppm, the ripening process is irreversibly initiated. The process may be slowed, but it cannot be reversed once it is truly under way. So, here is the key point: additional and externally applied ethylene, provided prior to the time that the naturally produced internal concentration reaches the required 0.1 – 1.0 ppm level, will trigger or initiate – “promote” if you will – this natural ripening process at an earlier time.
Doesn’t this still amount to an ‘artificial’ process?
No! The additional externally applied ethylene (the “gassing” so frequently referred to in the popular press) merely accelerates the normal ripening process. Numerous studies have shown that there are no important biochemical, chemical, or physiological differences between fruit ripened where the naturally produced ethylene has been the triggering mechanism or where additionally externally applied ethylene has triggered the process in the mature but unripe fruit.
Nevertheless, doesn’t the use of ethylene still allow the trade to ‘cheat’ the consumer with an inferior product?
For example, tomato fruit are not and cannot be “artificially reddened” by ethylene. The normal tomato ripening process, which includes pigment changes – the loss of green chlorophyll and conversion of carotenoids into red lycopene pigments – can be accelerated and brought about earlier by externally applied ethylene, but this is a normal process. In fact, some of the components of nutritional quality, such as Vitamin C content, benefit because of the fact that the fruits will be consumed after a shorter time interval from harvest as a result of ethylene treatments and hence, the initial level will not have degraded as far as the longer, un-accelerated process.
What are the factors that result in the poor quality tomatoes we often see on the market?
Although many factors could be listed, there are four which play the dominant role in determining the quality of tomato fruits presented to the customer in the retail store:
- Maturity at time of harvest
- Storage temperature during shipping and handling (this is probably the most common cause; tomatoes are often shipped or stored at improper temperatures, which causes severe taste loss…never allow tomato pulp temperature to go below 55°F!)
- Physical damage
1 – Source: California Fresh Market Advisory Board, Informational Bulletin No. 12, June 1, 1976.
Ethylene gas safe for ripening banana
LUCKNOW: Putting an end to the ambiguity over artificial ripening of bananas, the Food Safety and Standards Authority of India (FSSAI) has, in a letter issued to state governments, clarified that the use of ethylene gas to ripen bananas is safe. Also nipping in the bud the controversy over whose decision is supreme – the FSSAI or ministry of agriculture – the notification says that the decision has been arrived at “in consultation with the ministry of agriculture.”
Interestingly, the clarification letter, issued by assistant director general, PFA, Dhir Singh, to the state FDA is silent on the root of the problem — ethephon, the pesticide that produces ethylene gas.
Chief executive officer, FSSAI, VN Gaur, said: “There was some confusion over the use of ethylene gas for artificially ripening bananas. Now, we have set guidelines saying that controlled exposure of fruit to the gas is safe. Ethaphon, however, is a pesticide and over exposure of fruits to any pesticide is harmful.”
According to the norms prescribed in the notification, for the artificial ripening to be “legal”, unripe bananas must be exposed to ethylene gas “in low concentration exogenously to trigger their ripening.” Further, the authority clarifies that this procedure is considered safe “when used in concentration of 10-100ppm (0.001% to 0.01%) depending upon the crop, variety and maturity in the chambers at 18 to 24 degrees Celsius with 90% to 95% ReH (relative humidity).”
Significantly, while the clarification should bring cheer to traders as well as state FDA, it is not the end of the road for the problems yet. This time though, the cause of the troubles is that most artificial ripening setups available in Uttar Pradesh do not meet standards laid down by FSSAI in its current dictum. Under such circumstances, the state FDA will be well within its rights to continue cracking down on those flouting the prescribed norms. After these clear instructions, adulterators will now find it difficult to escape penal action.
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We Make Safety a Priority
When it comes to your livelihood, you don’t have time for costly mistakes. That’s why safety and consistency matter, and it’s why we’ve made them the hallmarks of our business. We strive to produce the high-quality ethylene generators and concentrate that used to be impossible to find. Your livelihood is important, but your safety takes precedence.
Choose a product that ripens fruit and preserves life – choose Catalytic Generators Australia
Ethylene application used to be unpredictable and dangerous, not to mention cumbersome. But over 40 years ago, Catalytic Generators created a way to do it better. We let you make ethylene, as needed, in your ripening room, versus storing large amounts of it in pressurized, bulky and hard-to-handle cylinders.
Our generators and Ethy-Gen® II make fruit ripening easier and safer!
Unlike compressed ethylene cylinders, there is absolutely no chance of ethylene explosion when using any of our generators as directed. However, a G-sized ethylene cylinder contains enough ethylene to reach the lower explosive limit (LEL) in most ripening rooms; in rooms that are 43 m3 or larger, you make ethylene as needed with our equipment and do it at such low concentrations that there is no concern of ethylene explosion.
Nitrogen / Carbon Dioxide mixed with Ethylene (“Ripe Gas,” “BANARG®” etc.)
These products are typically around 4% Ethylene with a 96% balance of an inert gas. It usually contains a large amount of Nitrogen to reduce the explosion possibility, but the inert gas quantity then requires an enormous amount of the gas mixture to be introduced to the ripening room in order to achieve proper ethylene ppm level. Sometimes the mix is made with Carbon Dioxide (CO2), which is a deterrent to the ripening process; rooms have to be vented to reduce CO2 levels, so using an ethylene product that releases more CO2 into the room is not very good practice.
Regardless of the inert used, this is usually a very expensive product when compared to ethylene from our Catalytic Generator. We will be glad to show you a cost comparison, so please contact us.
Don’t use Calcium Carbide to ripen fruit!
Several countries use Calcium Carbide as an artificial ripening agent. This is a dangerous and deadly process; when wet, the Calcium Carbide reacts with the water and produces acetylene gas, which mimics ethylene action and is used as an artificial ripening agent. However, acetylene is not nearly as effective as ethylene (much more must be used for it to be effective) and acetylene is not a natural plant hormone like ethylene. Also, this Calcium Carbide process will likely give off traces of arsenic and phosphorus, both highly toxic to humans. Furthermore, since so much acetylene is needed to mimic the ethylene action, this just intensifies the amount of toxic chemicals that are also introduced to the fruit. Consumption of fruits ripened with Calcium Carbide causes sever health problems; therefore, the use of this Calcium Carbide for ripening is illegal in most countries. Use only ethylene, the natural plant hormone & ripening agent!
Here are some reference articles on the dangers and illegality of using Calcium Carbide for ripening:
4 Food Safety and Standards Prohibition and Restriction on Sales Regulation 2011 and FAQ
Use of Banned Chemicals for Ripening Fruits
Consumers, beware of artificially ripened mangoes – The Hindu
SAFETY and EASE OF USE are why so many fresh produce companies across the world use our generators rather than gas cylinders, other ethylene application systems or Calcium Carbide. There are documented cases of explosions in ripening rooms where cylinders were in use. View our page on ethylene explosions.
Other reasons why our ethylene generators and Ethy-Gen® II Ripening Concentrate are superior:
The “use of cylinders of pure ethylene should be vigorously discouraged”.
The UK’s Health and Safety Executive/Local Authorities Enforcement Liaison Committee (HELA) explains that generators are the preferred options for ethylene application and that the “use of cylinders of pure ethylene should be vigorously discouraged.” For more information please click here.
Our Ethy-Gen® II Ripening Concentrate is the only ethylene ripening liquid that has passed the stringent standards of both the US-EPA and UK-CRD. So you can be sure of the purity and safety of what comes out of the ethylene generator when you only pour in Ethy-Gen® II!!
Ethy-Gen® II Ripening Concentrate is a visible product
This makes it easy to track inventory and reorder accordingly. With cylinders, how does the ripener know if there is 60% or 6% gas left in the cylinder? Likewise, how do you know that you are really buying a completely full cylinder? Without actually weighing the cylinder, you don’t… its guesswork. You can look at the pressure gauge and get an idea, but since you can see Ethy-Gen® II, you know you’ll have ethylene.
The Centralized Ripening System-CRSTM
The CRS requires less attention than cylinders, thanks to a large supply of Ethy-Gen® II connected to the system. This container will last over 4 times longer than a G cylinder of ethylene! Also, our system makes it easy to change containers, with quick disconnect fittings.
Our generators are listed by Underwriter’s Laboratories (UL®) or TÜV SÜD America, meaning that they have found our equipment to be safe from any foreseeable risk of fire, electrical shock, and related hazards, when used as directed. Catalytic Generators is the only ethylene generator company with products certified by both UL and TÜV.