저온진공열전달을 이용한 예냉 및 해동에 관한 실험적 연구

Abstract

To maintain the freshness of agricultural products, because of stand away between producer and its consumer, we need refrigeration system that can supply to consumer at cold chain as soon as gathering at the place of production.

General refrigeration system consists of refrigeration chamber or low temperature store. But the vacuum technology to cool down the products have the merits its rapid cooling down interval and saved refrigerator system.

Pre-cooling system suggests possibility get low pre-cooled temperature, suitable for fishes, meat, vegetables, fruit etc. Pre-cooling system have the advantage in quality maintenance through rapid refrigeration of ferment directly generate heat. Vacuum pre-cooling system's principle is that water saturated temperature is lowered according to the vacuum pressure established in the storage chamber, the temperature of products will be lowered consequently, due to the latent heat of evaporation of stored products. To establish appropriate vacuum in vacuum stored chamber, the rotary type vacuum pump was used to establish the desired vacuum pressure in the stored chamber, then water-driven gas suction ejector was used to maintain its vacuum pressure.

A number of thawing methods in current use have several disadvantages in melting time, discoloration and damage due to oxidation from the presence of warm air, weight loss caused by drying, partial cooking of the food extremities due to excess heat and high floor space requirements, capital costs and running cost.

These damages to efficient processing are, it is claimed, either eliminated or improved by the vacuum thawing.

An experimental study on the pre-cooling for the sprouted beans and cabbage and melting for hair tail and yellow-croaker by the low temperature vacuum system were carried out.

The cabbage cooling time with this pre-cooling vacuum system took about 60 minutes to reach from 23.2 (℃) to 4.5 (℃) at 5 (mmHg abs.). In case of sprouted beans took about 60 minutes to reach from 17.9 (℃) to 1.0 (℃) at 5 (mmHg abs.).

The quality for the cabbage and sprouted beans before and after experiments were in good condition with small weight loss.

The yellow croaker melting time with this low temperature vacuum melting system took about 170 minutes to reach from -10.3 (℃) to -0.8 (℃) at 20 (mmHg abs.). In case of hair tail took about 220 minutes to reach from -12.2 (℃) to 0.0 (℃) at 20 (mmHg abs.).

The quality for the yellow croaker and hair tail before and after experiments were in good condition with small weight loss.

The vacuum pre-cooling and melting system have the merit to compare with present systems in their short intervals to cooling down and to melt without any quality losses.