Technology for ripening fruits as important as marketing them

“How many times, have the bright red colour of the apples or the golden colored mangoes attracted you to buying them from the shelves?“For all that gloss and glitter: in reality the bright colour can contain lethal toxins dangerous for human health. The method used for ripening fruits must be given due care by farmers and traders as it decides the end use of the fruits — those consuming it,” says Dr. M. Selvarajan, Professor and Head, Department of fruit crops, Horticultural college and research institute, Periyakulam, Tamil Nadu.

“Lack of easier and rapid methods for uniform ripening poses a major problem in the fruit industry. Almost all methods of ripening, either conventional or the modern chemical methods, come with their own merits and demerits,” he explains.

Technologies

There are several technologies and methods available today for farmers for proper ripening.Normally the number of days taken for edible ripening varies for different fruits and prevailing climatic conditions.For instance, it takes about 5 to 6 days for mangoes and 6 to 7 days for sapotas to ripen. Under natural conditions, ethylene, a ripening hormone produced by the plant plays a major physiological role in the ripening process.

A simple technology practiced in households to trigger ripening is to keep un-ripened and ripened fruits together inside an air tight container.Since the already ripened fruits release ethylene, ripening will be faster. Another method is to place the fruits intended for ripening inside an air tight room and induce ripening through smoking inside smoke chambers.

Smoking chamber

Smoke emanates acetylene gas. Several fruit traders follow this technique to achieve uniform ripening especially in banana and mango.

“But the major drawback of this method is that the fruits do not attain uniform colour and flavour. In addition the persistence of smoke odour on the product impairs its quality,” adds Dr. Selvarajan.

In yet another practice some farmers dip unripe mature fruits in 0.1 per cent ethrel solution (1 ml of ethrel solution in 1 litre of water) and wipe it dry. 

The fruits are then spread over a newspaper without touching each other and a thin cotton cloth is covered over this. The fruits ripen in two days.Spreading unripe fruits as layers over paddy husk or wheat straw for a week to ripen is another alternative.

But these conventional methods possess some disadvantages like longer duration for ripening, high degree of spoilage due to excessive handling and lack of uniformity in colour development. About one-fourth of the fruits are spoilt by these methods, according to him.

In one of the simple and harmless techniques, 10 ml of ethrel and 2 gm of sodium hydroxide pellets are mixed in five litres of water taken in a wide mouthed vessel.

Ripening time

This vessel is placed inside the ripening chamber near the fruits and the room is sealed air tight. About a third of the room is filled with fruits leaving the remaining area for air circulation. Ripening of fruits takes place in about 12 to 24 hours. 

“In order to reduce the cost of chemical, some ethylene releasing fruits such as papaya and banana can also kept in the same room. Since ethrel is a plant hormone and hastens the ripening process by the release of ethylene in the atmosphere this practice may be the safest method,” explains Dr. S.P. Thamaraiselvi, Assistant Professor of the Institute.

Dangerous effect

Today many growers and traders use calcium carbide that emits acetylene gas. Fruits ripened using calcium carbide are carcinogenic and should not be consumed. Farmers and traders should become more aware about the dangerous effects in using the chemical.

“At our institute we are guiding farmers desirous of exporting their products using ethylene gas filled in pressurized cans for fruit ripening in 24-48 hours,” says Dr. Selvarajan.

For more information contact Dr. M. Selvarajan, Professor and Head, Department of fruit crops, Horticultural college and research institute, Periyakulam, Tamil Nadu, email: smselva8@gmail.com, mobile: 9003027732, phone: 04546-231726.

Courtesy : The Hindu