Cold storage

There are wide variety of foods and vegetables, which are grown in the country, which requires very specific temperature and humidity. The world over there has been a considerable development in post-harvest management practices of various horticulture crops. And there have been many technological innovations on cold chain to increase the self-life of horticulture products. At present there are about 3400 odd cold storages with an installed capacity of just over 10 million tonne in the country. The majority of cold storages are in the private sector accounting for about 91% of the installed capacity. The share of the cooperative sector is about 7% and that of the public sector is just over 1% of the total capacity of about 8 million tonnes that had been created in the potato growing states only. The term precooling refers to the rapid removal of field heat from the produce immediately after the harvest. Precolling is the first post harvest operation in the cold chain. Produce are living organisms that even after harvesting have an active metabolism. In addition, respiration, heat and respiratory gases and certain metabolic products such as carbonic acid, ethylene gases are released during the storage with undesirable consequences to the quality. It is found that a delay of one hour to start precooling of grapes after the harvest reduces the shelf life of grapes by a few days. In general, precooling is necessitated due to following reasons.

1. Products are perishable in nature and more so at high ambient temperature.

2. Products are seasonal but demand is continuous.

3. Increased awareness among the consumers for quality product.

4. If products are to be exported they have to be precooled, firstly to increase the shelf life and secondly to meet the international standard for quality.

5. The high ambient temperature causes the following effects.

6. Higher metabolic activity results in product ripening or ageing.

7. Increased moisture loss results in product drying and shrivelling

8. Increased growth of microorganisms causing decay of the products.

All these undesirable effects are temperature dependent, higher the temperature larger the damage and culminates in product quality degradation and shortening of shelf life. Therefore, by quick and uniform cooling after harvesting and subsequent maintaining of the products at optimum temperature the metabolic process is largely inactivated and the produce is brought to a dormant condition. Hence produce can be stored for a longer period of time without losing its freshness. Products can be precooled by any one of the following methods.

1. Vacuum cooling

2. Hydro cooling

3. Hydrair cooling

4. Forced cooling

Each of the above methods has its own advantages, disadvantages, suitability or otherwise to a particular product. It is found that invariably or otherwise to a particular product. It is found that invariably forced air-cooling or wet air-cooling can be used for precooling of all types of products as it offers the following advantages.

1 Simple and cheap.

2 Relatively short precooling time as produce is cooled rapidly through direct contact with cold humid air.

3 Minimum moisture loss because high relative humidity cold air passes over the fresh produce.

Produce retains original colour, taste, flavour and quality.

4 No frost formation.

5 Small installed cooling capacity for precooling with lower energy consumption.

1. It can be used as a forced air cooler, hydrocooler or hydraircooler.

2. It is modular in nature.

3. 5 tons of produce per batch and 2 to 3 batches per day can be processed.

4. It is compact.

5. Rapid cooling, precooling time is only 3 hours.

6. Humid air-no moisture loss.

7. Thermal storage facility to meet the instantaneous peak load in the beginning.

1. Need to carryout precooling within 2 hours of harvest.

2. Small medium farms and co-operative societies may not have facility in the near vicinity of the farm for carrying precooling process.

3. Fruits, vegetables and flowers are seasonal hence the requirement of precooling may shift from one place to another.

Under above Indian conditions a need for mobile precooler having a capacity of 1 metric ton of produce per batch which can be located/relocated from farm to farm and one place to other depending upon the harvest plan and needs of small/medium farm or co-operative society. The precooled produce can be transported to nearest cold storage under preserved condition.

Cold storage technology

In recent years there has been great improvement in the technology of refrigeration. Controlled atmospheric storage has come to stay. In India traditionally ammonia and freyon have been used as refrigeration. The latter is responsible for the degradation of ozone layer and its use is under great pressure from those who are concerned over the environment. The cold storages set up in 1980’s are mostly having de-fuser cooling system that consumes more power in comparison with gravity or pin coiled cooling system. New technology like prefeb sandwich insulated panels may have to be adopted for the construction of new units that could help in better efficiencies with low maintenance costs and substantially less time taken in construction. Normally cold storages are using vapour compression refrigerator system.

Ag.
Technologies
(Hi-Tech Agriculture)