Fruits must be picked when immature because they will not ripen naturally. However, there are instances when this is inevitable, such as during a storm or unavoidable circumstances. Researchers were conducted at UP Los Baños have shown that immature fruits can somehow be made to ripen with the aid of a chemical, ETHREL.

Procedure:

Bananas
1. Fill with water up to ½ a kerosene can (balde). Dissolve 10 tbsp. ethrel in this water.
2. Pour more water gradually until the can is full (19 liters) and stir well while pouring.
3. Transfer one-half of this to another container.
4. Immerse the bananas in the mixture for 5 minutes, then let it dry in the air. These will ripen in 5 days.
5. If the mixture will be used again cover it and store in a cool place.

This can be used up to 15 days provided the fruits being immersed are clean and dry before they are immersed.
It was seen by the researchers that if the fruits are immersed in ethrel on the fourth to the seventh day (4th-7th) after harvest, the bananas ripen in 2-3 days.

Tomatoes
1. For immature tomatoes, 90% of 21 day-old fruits ripen in 10 days after putting them in ethrel. Some of these did not turn red.
2. If the ethrel solution is weak, tomatoes do not ripen well.
3. If the tomatoes are less than 21 days tomatoes are not edible.

Calcium chloride and ethrel:
Less ethrel is needed to ripen bananas, compared to calcium carbide. It requires 20 grams carbide for every liter of water.

Source: Agricultural & Industrial Life