While formalin, a chemical seriously harmful to people, is routinely used to preserve mangoes, fish, fruit and vegetables, Bangladeshi scientist Dr Mubarak Ahmad Khan has found an alternative.

After long research, the chief scientific officer of the Bangladesh Atomic Energy Commission found that chitosan, made naturally from discarded shrimp shells, can replace formalin in food preservation. It is cheap and harmless to people. He has already used it successfully on various fruits and vegetables; next it will be tested on fish, followed by commercial use.

After three years of research, chitosan kept mangoes fresh for two to three weeks, litchi for 12 to 13 days, pineapple for 10 to 12 days, frozen bitter gourd for about 18 days and tomatoes for 21 days, without changing quality, shape, colour or taste.

Chitosan can be produced from local raw materials. One taka's worth is enough for a kilogram of mangoes commercially, and 40 paisa for vegetables. A kilogram of shrimp gives 60 grams of shell, and six kilograms of shell make a kilogram of chitosan at a cost of 20,000 taka, against 100,000 taka for chemically made chitosan in India. The shells are washed in 3 per cent sodium hydroxide (caustic soda) to make chitin, which is converted to chitosan by gamma irradiation, a food-safe process approved by the World Health Organization (WHO) and the US Food and Drug Administration (FDA). No other chemicals are used, so it does not pollute.

The discovery was presented at a meeting at the Prime Minister's Office, and a 13-member committee of secretaries, directors general, BUET chemical engineers and Dhaka University professors was formed. Other research institutes have been asked to verify it, and work on fish has been approved.

According to the report, Bangladesh's shrimp output yields about 15,000 tonnes of shell a year, enough for 250 tonnes of chitosan, which scientists consider sufficient for food preservation. Dr Mubarak said he is considering patenting the process.

Source: Staff Correspondent, The Agro News. First published in Bengali on The Agro News.