Excerpts of a meeting on Artificial Fruit Ripening held at Department of Food Safety, Government of Delhi

The meeting was chaired by Sh. K J R Burman, Secretary cum Commissioner Food Safety, Delhi Government and was attended by Dr. KK Aggarwal, President Heart Care Foundation of India; Dr. Ram Asrey from IARI, Dr. R.K. Sarin from Forensic Dept Delhi Government, Dr. S.K. Manocha from FICCI, Dr. Sanjay Rajput and Dr. J.S. Chauhan from SIIR apart from officials from Department of Food Safety.

·        To meet demands, 90% of the fruits in the market today are using artificial ripening methods.

·        Ripening agents allow many fruits to be picked prior to full ripening, which is useful, since ripened fruits do not ship well. For example, bananas are picked when green and artificially ripened after shipment after being treated with ethylene. Catalytic generators are used to produce ethylene gas simply and safely. Ethylene sensors can be used to precisely control the amount of gas.

·        Climacteric fruits (papaya, banana and mango) are able to continue ripening after being picked, a process accelerated by ethylene gas. 

·        Non-climacteric fruits can ripen only on the plant and thus have a short shelf life if harvested when they are ripe. Examples are grapes, jamun, kinnu, lemon and citrus fruits.

·        Calcium carbide is also used for ripening fruits artificially.  Calcium carbide reacts with water to produce acetylene, which acts as an artificial ripening agent.  Industrial-grade calcium carbide may contain traces of arsenic and phosphorus, which makes it a human health concern. The use of this chemical for this purpose is illegal in India. Calcium carbide releases phosphine gas, arsine gas, acetylene gas and all of them are toxic to the body.

·        Natural ripening of fruits occurs from inner to outer layer, while artificial ripening starts from the surface to the inner areas. Therefore, naturally ripened mango will be sweeter in the center and the artificially ripened fruit will be sweeter on the surface.

·        Iodine can be used to determine whether fruit is ripening or rotting by demonstrating if the starch in the fruit has turned into sugar. For example, a drop of iodine on a slightly rotten part (not the skin) of an apple will turn a dark-blue or black color, since starch is present. If the iodine is applied and takes 2–3 seconds to turn blue/black, then the process has begun but is not yet complete. If the iodine stays yellow, then most of the starch has been converted to sugar.

·        Storage of potatoes at 10–12°C with CIPC treatment is helpful in providing the consumers potatoes, which are not sweet in taste, during the summer and rainy seasons.

·        Ethylene is also a gaseous plant hormone. Early examples of the human utilization of ethylene to enhance fruit ripening include the ancient Egyptian practice of gashing figs to enhance ripening responses. 

The ethylene produced by the injured fruit tissue triggers a broader ripening response.  Similarly, the ancient Chinese practice of burning incense in closed rooms with stored pears (ethylene is released as an incense combustion by-product) stimulates ripening of the fruit.  

The idiom ‘one bad apple spoils the barrel’ is based upon the effect of one apple ripening (or rotting) and emitting ethylene which accelerates the ripening and senescense of apples stored with it. Another idiom is ‘Kharbuje ko dekh kar kharbuja rang badalta hai’.

·        Strategies to minimize fruit exposure to external sources of ethylene and treatments for managing the internal ethylene concentration are the key to commercial optimization of storage life and eating quality of many fruits. 

·        Respiration is a process of oxidative breakdown (catabolism) of complex molecules into simpler molecules, yielding energy, water, carbon dioxide and simpler molecules needed for other cellular biochemical reactions required for ripening.  The respiration rate per unit of fruit weight is (as a general rule) highest in immature fruit, with the respiration rate declining with age.  Thus respiration rate of fruit is an indicator of overall metabolic activity level, progression of ripening and potential storage life of the fruit (i.e. a low respiration rate means that the energy reserves will take longer to be consumed and the fruit can be stored for longer). 

Some fruits show a significant variation to the pattern of declining respiration rate during their ripening. They exhibit a distinct increase in respiration rates (a respiratory climacteric) of varying intensity and duration, commensurate with ripening.  Fruit that exhibit this characteristic increase in respiration rate are classified as ‘climacteric’ whereas fruits that follow the pattern of steadily declining respiration rate through ripening are classified as ‘non-climacteric’.

   

To find out whether a fruit is respiring or not, one can either use a respirometer which can measure the carbon dioxide outcome or one can put a fruit in a polythene bag and tighten it and look for presence of vapors on the surface after one hour.

·        Low temperature modulates the ripening of kiwifruit or banana in an ethylene-independent manner, suggesting that fruit ripening is inducible by either ethylene or low temperature signals.

·        Ethylene gas ripening can be detected by phenolphthalein test.

·        Arsine and phosphine gas can be deposited on the surface of the fruit.

·        Other natural ripening methods are by putting them in rice, straw (bhusa), wheat etc.

·        Everyone should know that gases produced by ripening can worsen or cause asthma in children.

·        Gama radiation technology is used in fruits either for disinfection or delaying the ripening process so that they can be exported.