Compared with developed countries, the development of quick-frozen food in our country started very late. Although the development speed is very fast now, with an annual growth rate of more than 25%, the annual per capita consumption of quick-frozen food in our country is only one tenth of that in developed countries. With the continuous growth of the income level of our residents and the continuous acceleration of the pace of life, IQF Freezing food has great room for development. With the development of food quick-freezing industry and quick-freezing food industry, quick-freezing equipment has now become an indispensable food processing equipment.
First of all, what are the factors that affect the quick freezing of food?
Under the condition that the food freezing speed is 5-50mm thick per hour, the quantity and size of ice crystals generated in the food freezing process can be ensured to be basically unchanged, and the crystal grains are relatively fine, so that the reversibility of preservation is achieved. Factors Affecting Quick Freezing of Food;
- Cooling medium temperature: The freezing speed and freezing point of food are directly proportional to the temperature difference Δt of cooling medium. The lower the temperature of the cooling medium, the faster the freezing speed.
- Impact of frozen goods on the wind: the surface area of the wind, the wind speed and the circulation rate of the cold wind affect the freezing speed: tests show that it takes 120 minutes for green beans to be placed in a -30 degree cooling medium at 0 wind speed and only 10 minutes at 4.5m/s wind speed.
- Influence of latent heat and enthalpy difference: 80kcal cold is required for 1kg of water to be reduced from 80 degrees to 0 degrees, and 80kcal cold is also required for changing from 0 degrees of water to 0 degrees of ice. It can be seen that latent heat of crystallization requires more cooling capacity. Similarly, when the enthalpy difference is large, such as the purchase temperature is high, it requires not only a large amount of cold energy but also a long freezing time.
- Influence of food composition: Foods with high thermal conductivity freeze faster than foods with low thermal conductivity. If plastic film is applied on the surface of foods, it will not only conduct heat slowly, but also hinder the wind. Such as water thermal conductivity of 0.604w/mk, fat thermal conductivity of 0.15, plastic film thermal conductivity of 0.028, wind thermal conductivity of 0.066.
- The influence of food thickness: the sum of squares of food thickness is directly proportional to the quick freezing time. The thicker the food, the longer the quick freezing time.
From the factors affecting the quick freezing of food, we can know that the temperature of the cooling medium rises and fluctuates, reducing Δ t, because the quick freezing warehouse has a large quantity of food and relatively high temperature food. The Quick Freezing Equipment keeps the indoor temperature almost unchanged. As static food is placed in the quick-freezing warehouse, the wind is not uniform and even the wind speed is reduced. Static unidirectional blowing hinders the crystallization speed of the frozen product center, i.e. the windblown part. The surface area of each monomer in the quick-freezing equipment tunnel is large and uniform, and freezing is accelerated due to the change of wind direction. As the food entering the quick-freezing warehouse reaches latent heat at the same time, it is necessary to suddenly and greatly increase the cooling capacity to face the crystallization process, resulting in temperature rise and prolonged crystallization time.