Delhi's department of food safety held a meeting on artificial fruit ripening recently. K J R Burman, the state food safety commissioner, chaired the meeting, which was attended by K K Aggarwal, president, Heart Care Foundation of India; the Indian Agricultural Research Institute's (IARI) Ram Asrey; R K Sarin of Delhi's forensic department; S K Manocha of the Federation of Indian Chambers of Commerce and Industry (FICCI); Sanjay Rajput and J S Chauhan from Shriram Institute for Industrial Research (SIIR) and officials from the food safety department.
“To meet the demand, about 90 per cent of the fruit sold in the market nowadays have been ripened using artificial methods. Ripening agents allow many fruit to be picked prior to full ripening, which is useful, since ripened fruit 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,” a source, on condition of anonymity, stated.
He added that there are two kinds of fruit – climacteric fruit (such as papaya, bananas and mangoes) and non-climacteric fruit (such as grapes, jamun, kinnow, lemons and other varieties of citrus fruit). Explaining the difference between the two, he said, “Owing to the use of ethylene gas to accelerate the process, climacteric fruit are able to continue ripening after they have been picked. Non-climacteric fruit are those who ripen only on the plant, and thus, have shorter shelf lives if harvested when they are ripe.”
“Natural ripening of fruit occurs from the inner layer to the outer layer, while artificial ripening occurs from the surface to the inner areas. Therefore, naturally-ripened mangoes would be sweeter at the centre, while artificially-ripened ones would be sweeter on the surface,” the source explained.
Calcium carbide
Calcium carbide is also used to ripen fruit artificially. It reacts with water to produce acetylene, which acts as an artificial ripening agent.
The source said, “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 and acetylene gas. All these gases are toxic to the body.”
Iodine
Iodine is used to determine whether the fruit is ripening or rotting.
An experiment is conducted to determine whether the starch in the fruit has turned into sugar. If a drop of iodine (which is yellow) is put on a slightly rotten part (but not the skin) of an apple, it will turn dark blue or black, because starch is present in the sugar. If, upon application, the iodine takes two or three seconds to change colour, the process has begun, but is not complete. If it stays yellow, most of the starch has converted into sugar.
CIPC-treated potatoes
“Storage of potatoes at temperatures ranging between 10 and 12 degrees Centigrade with Chlorpropham (CIPC) treatment is helpful in providing consumers potatoes that do not taste sweet in summer and during the monsoon,” the source said.
Ethylene
The source stated that ethylene – which is also a gaseous plant hormone – was used by the ancient Egyptians to gash figs to enhance the ripening response. Another early example of the human utilisation of ethylene to stimulate fruit ripening is the ancient Chinese practice of burning incense in closed rooms with stored pears (ethylene is a by-product of the combustion of incense). He added that the ethylene produced by the injured fruit tissue triggers a broader ripening response.
“Strategies to minimise the exposure of the fruit to external sources of ethylene and treatments to manage the internal ethylene concentration are the keys to commercial optimisation of the shelf life and quality of many fruits,” the source said.
Low temperatures modulate the ripening of kiwifruit or bananas 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 the phenolphthalein test.
[In fact, the English expression, “One bad apple spoils the whole bunch” (which means, “The wrongdoings of one person can affect a whole group of people”) is said to be based on the effect of the ripening or rotting of an apple, which emits ethylene, which in turn accelerates the ripening and senescence of the fruit that is stored with it.]
Respiration
Respiration is the process of oxidative breakdown – also known as catabolism – of complex molecules into simpler molecules that yield energy, water and carbon dioxide and simpler molecules which are needed for other cellular biochemical reactions required for ripening.
The respiration rate per unit of fruit weight is (as a general rule) the highest in immature fruit, and it declines with age. Thus the respiration rate of fruit is an indicator of its overall metabolic activity level, the progression of ripening and the potential storage life of the fruit. A low respiration rate means that the energy reserves will take longer to be consumed, and the fruit can be stored for longer.
“To meet the demand, about 90 per cent of the fruit sold in the market nowadays have been ripened using artificial methods. Ripening agents allow many fruit to be picked prior to full ripening, which is useful, since ripened fruit 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,” a source, on condition of anonymity, stated.
He added that there are two kinds of fruit – climacteric fruit (such as papaya, bananas and mangoes) and non-climacteric fruit (such as grapes, jamun, kinnow, lemons and other varieties of citrus fruit). Explaining the difference between the two, he said, “Owing to the use of ethylene gas to accelerate the process, climacteric fruit are able to continue ripening after they have been picked. Non-climacteric fruit are those who ripen only on the plant, and thus, have shorter shelf lives if harvested when they are ripe.”
“Natural ripening of fruit occurs from the inner layer to the outer layer, while artificial ripening occurs from the surface to the inner areas. Therefore, naturally-ripened mangoes would be sweeter at the centre, while artificially-ripened ones would be sweeter on the surface,” the source explained.
Calcium carbide
Calcium carbide is also used to ripen fruit artificially. It reacts with water to produce acetylene, which acts as an artificial ripening agent.
The source said, “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 and acetylene gas. All these gases are toxic to the body.”
Iodine
Iodine is used to determine whether the fruit is ripening or rotting.
An experiment is conducted to determine whether the starch in the fruit has turned into sugar. If a drop of iodine (which is yellow) is put on a slightly rotten part (but not the skin) of an apple, it will turn dark blue or black, because starch is present in the sugar. If, upon application, the iodine takes two or three seconds to change colour, the process has begun, but is not complete. If it stays yellow, most of the starch has converted into sugar.
CIPC-treated potatoes
“Storage of potatoes at temperatures ranging between 10 and 12 degrees Centigrade with Chlorpropham (CIPC) treatment is helpful in providing consumers potatoes that do not taste sweet in summer and during the monsoon,” the source said.
Ethylene
The source stated that ethylene – which is also a gaseous plant hormone – was used by the ancient Egyptians to gash figs to enhance the ripening response. Another early example of the human utilisation of ethylene to stimulate fruit ripening is the ancient Chinese practice of burning incense in closed rooms with stored pears (ethylene is a by-product of the combustion of incense). He added that the ethylene produced by the injured fruit tissue triggers a broader ripening response.
“Strategies to minimise the exposure of the fruit to external sources of ethylene and treatments to manage the internal ethylene concentration are the keys to commercial optimisation of the shelf life and quality of many fruits,” the source said.
Low temperatures modulate the ripening of kiwifruit or bananas 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 the phenolphthalein test.
[In fact, the English expression, “One bad apple spoils the whole bunch” (which means, “The wrongdoings of one person can affect a whole group of people”) is said to be based on the effect of the ripening or rotting of an apple, which emits ethylene, which in turn accelerates the ripening and senescence of the fruit that is stored with it.]
Respiration
Respiration is the process of oxidative breakdown – also known as catabolism – of complex molecules into simpler molecules that yield energy, water and carbon dioxide and simpler molecules which are needed for other cellular biochemical reactions required for ripening.
The respiration rate per unit of fruit weight is (as a general rule) the highest in immature fruit, and it declines with age. Thus the respiration rate of fruit is an indicator of its overall metabolic activity level, the progression of ripening and the potential storage life of the fruit. A low respiration rate means that the energy reserves will take longer to be consumed, and the fruit can be stored for longer.
Some fruit 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 (an instrument that measures the carbon dioxide outcome) or put a fruit in a polythene bag, tighten it and look for the presence of vapours on its surface after one hour.
Notes
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 either cause or worsen asthma in children.
Gamma radiation technology is used in fruit, either to disinfect them or delay their ripening process, so that they can be exported.
To find out whether a fruit is respiring or not, one can either use a respirometer (an instrument that measures the carbon dioxide outcome) or put a fruit in a polythene bag, tighten it and look for the presence of vapours on its surface after one hour.
Notes
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 either cause or worsen asthma in children.
Gamma radiation technology is used in fruit, either to disinfect them or delay their ripening process, so that they can be exported.
