What type of chemistry is occurring as fruit ripens

Even when people are not officially performing experiments, they are still acting like scientists—making observations and developing theories. In this project, we investigate whether storing a green banana by itself in a closed bag to trap ethylene ripens faster than a banana left on the counter.

We also look at whether storing the banana with another piece of ruit apple or orange affects the ripening time. The banana left on the counter is very important because it is our experimental control. Other factors affecting ripening can also be investigated using this same type of procedure.

Try ripening different fruits like avocados or pears instead of bananas. Or you could try using different places of storing the b anana like a colder basement or a warmer windowsill. See if the type of bag—paper or plastic—affects the results.

Make observations—the bananas should all have a similar appearance. Set aside one banana. 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. The receptors are negative regulators and in the absence of ethylene, constitutive Triple Response CTR1 gets activated.

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 [ 12 ].

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 [ 13 ]. 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 [ 14 ].

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. 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 [ 16 ].

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 [ 4 ].

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 [ 17 ]. 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 [ 18 ].

It has been reported that ethylene is involved in regulation of genes related to anthocyanin biosynthesis [ 19 ]. 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 [ 20 ].

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 [ 21 , 22 ].

Further [ 23 , 24 ] 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 [ 25 ]. 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 [ 26 ]. Banana Musa spp.

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 countries throughout the tropical and subtropical regions of the world [ 27 ]. It is recorded as the fourth largest food crop of the world after rice, wheat, and maize [ 28 ]. The annual world production of bananas is around million metric tons from an area of 5.

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, ha 20,ha and 40,ha in wet zone and dry and intermediate zones respectively of land is under banana cultivation. There were twenty-nine banana cultivars and two wild species in Sri Lanka [ 31 ].

According to a case study in Sri Lankan crop sector [ 32 ] currently there are 55 local cultivars in Sri Lanka. 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, , the total production of banana is nearly , MT annually. 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. 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.

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 [ 34 ] 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 [ 35 , 36 ]. Burg and Burg [ 37 ] reported that low ethylene concentration as 0. Dominguez and Vendrell [ 36 ] showed that exogenous ethylene, ppm treatment for 12 hours, can immediately increase the endogenous ethylene and CO 2 production similar to respiratory climacteric. Further this study showed that increment in respiration depends on time of treatment whereas hour treatment was slightly effective than 6 hours treatment.

Lohani [ 38 ] noted fold decrease in fruit firmness which occurred within two days after exogenous ethylene treatment. 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 [ 39 ] 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 hours while control samples were remain unripe after same period of time. According to Burg and Burg [ 37 ] acetylene has a lower biological activity than ethylene and it was reported in this study that concentration of acetylene should be 2.

However Thompson and Seymour [ 40 ] reported that bananas do not respond to acetylene at 0. However, calcium carbide is not generally recognized as safe [ 41 ] and prohibited in Sri Lanka as in most countries under Section 26 of the food labelling and miscellaneous regulation of Calcium carbide is considered as hazardous due to several reasons.

Commercial calcium carbide contains traces of arsenic and phosphorous hydride [ 42 , 43 ] and acetylene emitted from commercial calcium may also contain up to 3 ppm arsenic and up to 95 ppm phosphorous hydride [ 42 , 44 ]. 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 [ 42 ].

Exposure to acetylene gas can cause headache, vertigo, dizziness, delirium, seizure, and even coma [ 43 ]. 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 [ 45 ] and has been shown to hasten ripening of several fruits including bananas, apples, tomatoes, mango, peaches, citrus fruits, and guava [ 46 — 48 ]. Pendharkar [ 49 ] treated bananas with different concentrations of ethephon. Here it was found out that different concentrations of ethephon significantly influence chemical changes during ripening and ppm was found as the best concentration of ethephon for early ripening.

Nair and Singh [ 50 ] showed that prestorage treatments of mangoes Mangifera indica L. 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 [ 48 ]. 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. The cause of fruit ripening is a natural form of a chemical synthesized to make PVC polyvinyl chloride piping and plastic bags—namely, a gaseous plant hormone called ethylene. For thousands of years, people have used various techniques to boost ethylene production even if they did not quite know it.

Ancient Egyptian harvesters slashed open the figs they collected to stimulate ripening, and Chinese farmers would leave pears in closed rooms with incense burning. Later research showed that wounding and high temperatures trigger plants to produce ethylene. In Russian scientist Dimitry Neljubow showed that ethylene could affect plant growth after he identified it as the active ingredient in vapors leaking from a gas main. The vapors were causing surrounding plants to grow abnormally.

Three decades later, researchers found that plants not only responded to ethylene, but they could produce their own, and production of the gas increased when the scientists cut injured the fruit with a knife. Researchers later discovered that plants produce ethylene in many tissues in response to cues beyond the stress from heat and injury. It is made during certain developmental conditions to signal seeds to germinate, prompt leaves to change colors, and trigger flower petals to die.

For this, Edinburgh Sensors are the market leaders with over forty years of experience developing highly sensitive, rapid response near-infrared sensors for detection of hydrocarbon gases and CO 2. There are two versions of the Gascard NG available. It can be purchased either as the stand-alone card or as the Boxed Gascard 11 , that contains the Gascard NG card inside but in a pre-built housing to minimise installation and set-up time. For example, The Gascard can detect CO 2 concentrations in the range of 0 — ppm.

Another powerful feature of the Gascard NG is that, by using RS communications, the Gascard can be integrated with other control or data logging devices easily and there is also with the option for onboard LAN support where required. This means it is relatively straightforward to set up feedback systems to constantly monitor, log and adjust the atmosphere around the fruit, ensuring the produce is always at its best.

With the ability to reduce waste — ripening fruit may overripen other nearby fruit — optimise ripening at the time of sale and improve product quality, Edinburgh Sensors instruments offer cost-efficient and high-quality devices for online monitoring of CO 2 levels. We hope you have enjoyed learning more about how our range of products can help in the process of fruit ripening.