RIPENING OF FRUITS
During ripening, the starch in the fruit breaks down to form sugar. The fruit skin changes colour, going from green to a bright red (apples & tomatoes) or yellow (mangoes, bananas and lemons). These changes attract birds and animals, who love to eat the sweet flesh. They throw away the seeds, which fall on the ground and germinate.
The ripening of a fruit depends on the season. For example, we get mangoes only in summer and apples only in winter. The plant can detect changes in season by changes in temperature and humidity. It then produces ethylene which spreads across the plant. When ethylene reaches the fruit, it sends a signal to all the cells in the fruit. The cells then make enzymes that break starch into sugar. The cells in the skin start making pigments which give the fruit its colour.
When a fruit ripens, it still has a lot of acid. But there is so much sugar in it, that it masks the sour taste of the acid!
ARTIFICIAL RIPENING
Ripe fruits cannot be stored and transported for a long time. Hence farmers in fruit orchards pluck the fruits raw. The natural ethylene in the fruits makes them ripen, so that they are ready to eat by the time you buy them.
Sometimes the fruits are not yet ripe when they are ready to be sold. Hence they have to be artificially ripened. Fruits are kept in hay-lined wooden boxes called crates. These crates are stacked on shelves and a wood fire is lit below them. The smoke contains ethylene and acetylenes gases, which induce ripening.
Sometimes, fruits are placed in a room in which ethylene gas or acetylene gas is introduced. In another method, calcium carbide (CaC2) is applied over fruits. It reacts with moisture to form acetylene.
Calcium Carbide is a chemical compound which is mainly used for welding purposes. The commercially produced calcium carbide is grayish white in color. The color varies depending on the grade. The main use of calcium carbide is in the production of acetylene. REASONS FOR USING CALCIUM CARBIDE
Mostly calcium carbide is used to ripen fruits like mangoes, bananas and papayas. Traders prefer calcium carbide because the cost of 1 kg of calcium carbide is Rs.30 and it can ripen 10 tonnes of fruits. Usually the traders keep small packets of the chemical near the pile of bananas or the boxes of mangoes. The boxes are kept in dark rooms for one to two days.The chemical reaction takes place due to the moisture content present in the fruit and acetylene gas is produced which enhances the ripening of fruits.
The disadvantages of artificial ripening
1. Calcium carbide is a carcinogenic chemical compound. It causes many short term and long term health problems.
2. The short term exposure to the chemical causes diarrhoea, irritation in the eyes, headache, dizziness and thirst.
3. The chronic exposure to the chemical results in mouth ulcers, food poisoning and even cancer.
4. Calcium Carbide is also hazardous for people who handle it. The chemical can cause severe seizures and blisters when it is touched with wet hands.
5. The artificially ripened fruits are toxic and also tasteless though they have a very appealing color.
6. The organic composition and the nutritional value of the fruit is also lost when it is artificially ripened.
2. The short term exposure to the chemical causes diarrhoea, irritation in the eyes, headache, dizziness and thirst.
3. The chronic exposure to the chemical results in mouth ulcers, food poisoning and even cancer.
4. Calcium Carbide is also hazardous for people who handle it. The chemical can cause severe seizures and blisters when it is touched with wet hands.
5. The artificially ripened fruits are toxic and also tasteless though they have a very appealing color.
6. The organic composition and the nutritional value of the fruit is also lost when it is artificially ripened.
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