Preserve foodstuffs properly

Food storage is the method of preserving food products for the future from the attack and damage of various pathogens. The main objective of effective food preservation is to preserve as much of the original properties and nutritional value of the food as possible. Traditional methods and techniques are still used in Bangladesh to preserve and prevent spoilage of foodstuffs. Among these, the use of salt, smoke, sugar, vinegar, and drying are significant. Modern food preservation methods have enabled the preservation of many types of food.

The main methods of food preservation include sun drying, application of heat, extreme cold storage of food, use of various chemicals and application of radioactive radiation. The method of preserving food by drying it in the sun is very old and it is widely used in preserving fish, fruits, grains, vegetables, meat etc. in Bangladesh. The method of drying and preserving fish and meat is believed to have been used since ancient times.

Even about 100 years ago, dry vegetables were sold. In Chittagong, Cox's Bazar, St. Martin's Island, Sonadia and many coastal areas of Bangladesh, fish are regularly dried and stored. Large quantities of fish are dried each year for local consumption and export. Among the fruits, the tradition of drying mangoes and plums still exists. Freezing methods of food preservation are generally limited to cities. Although this is one of the most convenient ways to preserve food, this method does not destroy microorganisms, nor can their growth be completely prevented.
Vegetables, meat, milk, fish, eggs, butter and other perishables are usually stored in refrigerators for daily use in households. Decomposition is largely halted by extreme cold, but fermentative action continues in uncooked food. Currently there are many private and government cold storage facilities across the country. They are playing an important role in the preservation of different varieties of potatoes.

The method of preserving food by canning through the use of high heat is expensive but does not have the effect of microorganisms and ferments. Food containers are tightly sealed to protect against bacterial contamination. Several organizations in the country are now preserving and marketing fish, meat, vegetables, fruits, soft drinks etc. in this way. Pickling is one of the most common methods of inhibiting microbial growth by using acetic acid, a component of vinegar. A variety of pickles are prepared in Bangladesh at household and institutional level with the addition of vinegar, mustard oil and some spices.

Various chemicals have been used in food preservation for centuries. Commonly used agents include sodium chloride, sodium and potassium nitrate, sodium salicylate, benzoic acid, ascorbic acid, vinegar, alcohol, etc. A very thick sugar solution is widely used in Bangladesh for making jellies and jams. Salt has been used in food preservation since ancient times. Along with salt preservation, sun, heat and smoke are also used. Table salt is mainly used in this country to preserve hilsa fish.
Irradiation preservation is the process of preserving food by applying safe levels and scientific methods of radiation release, which inhibits the attack and growth of pests and microorganisms and thus increases the shelf life of preserved food. According to an estimate by the Food and Agriculture Organization of the United Nations, about one-fifth of the world's food crops are affected by insects, microorganisms and other pests. In many developing countries where high temperatures and high humidity prevail, the loss reaches close to 50 percent.

The nutritional value of certain foods can be improved by using irradiation processes. Bangladesh Atomic Energy Commission's Institute of Food and Radiation Biology conducts research on increasing the life span of various types of foods. The government of Bangladesh has already granted unconditional approval for 13 irradiated food items declared fit for human consumption, including potato, onion, wheat flour, spices, chicken meat, fish and fish products, frozen shrimp, rice products, various pulses, papaya and mango.

Food and Radiation Biology is the responsible national organization for the implementation of food irradiation application technology for sterilization of food and agricultural products and their quality improvement. Research on the application of radiation to food is mainly carried out with a suitable gamma radiation source installed in food and radiation biology institutes.

Post-harvest losses of stored food grains are as high as 10-25 percent in Bangladesh. Insect and fungal attack during storage is partly responsible for this. Post-harvest losses are largely dependent on proper threshing, cleaning, drying and storage. Drying is the removal of excess water by keeping the right amount of water in the grain. In Bangladesh, food grains are sun-dried in the traditional way. Sun drying of agricultural produce is the most widely followed method in the country.

The primary goal of storage is to prevent deterioration of grain quality. The work is done indirectly rather than directly by humidity control, free air circulation and prevention of germs, insects and rodents. Farmers in Bangladesh store food grains to meet their food needs and use them as seeds. The grain stored can be roughly 10-100 percent of the total production. Cereals are stored in containers. The vessels used for this purpose in Bangladesh include matka, jute sack etc. Large quantities of grain are stored in traditional storage systems.

80% of the total grain production is stored in rural areas and this is done through traditional storage systems. Traditional techniques are rooted in cultural norms and are passed down through generations. The size and capacity of the barn is determined by the type of feed and the amount of grain. About eight types of storage systems are used at the farm level in Bangladesh. These include medium and large-sized rectangular containers made of cane or bamboo, medium-capacity containers made of bamboo, and dole or small-capacity containers made of bamboo. The most commonly used items made of bamboo are doles and fences.

Bagged grain is stored in barns. These are known as ordinary barns. At the regional level there are central barns in the rural and urban areas. Local and central storages are mainly used as short-term storage of food grains. These food grains are collected from farmers during harvest season or brought from other local and central storages. They also store imported grains for dispatch to other local depots, central depots and ration shops. Silos are used to store food grains, especially wheat, as a food security measure in times of emergency in the country.

The use of high temperature dryers used in developed countries is not economically viable in Bangladesh. Due to abundant solar radiation in all parts of the country, sun drying is widespread here. The solar-dryer trend appears to be both promising, environmentally sound and pollution free. Application of mechanical dryers/solar thermal sterilizers for limited quantities of seeds and batch-type drying and storage methods for large quantities of seeds may be feasible for Bangladesh.

The writer is Columnist , Official of Southeast University, Dhaka