When quick-frozen vegetables are made, many types are frozen before packaging, which can reduce a lot of freezing time and improve product quality. In order to prevent the thin and brittle blade from being broken, it can be packed first and then frozen. In freezing, quick-frozen vegetables must be packed with suitable materials, which can reduce the sublimation of ice crystals. This sublimation will cause the color of the product to change, and the taste will also change. After burning, the taste will not be delicious, thus losing the brittleness, and some will also change the quality of the product.
The dry consumption of quick-frozen vegetables from the surface sublimation in unit time can be explained by the following formula W=β*F(Pg-Pr), where β is the coefficient of convective mass transfer, and (kg/m2*s*Pa )F is the surface area of ​​the food, (m2)Pg is the pressure of the water vapor on the surface of the food, (Pa)Pr is the pressure of the water vapor of the main body of the air, as can be seen from the above formula, for quick-frozen vegetables, it The values ​​of β and F are specified, and the dry consumption of sublimation is generally proportional to the difference in the pressure of water vapor. Therefore, in order to avoid dry consumption of the product, one must prevent the fluctuation of the temperature of the warehouse and cause the difference in the pressure of the water vapor to become larger; the second is to use a material with high air tightness for packaging.
It is necessary to select the material with the lowest possible water vapor and gas permeability and strong physical impact at low temperatures. With good materials, proper methods are also needed. If the sealing of the packaging bag is not good, the water vapor will move from the vegetable surface to the space. The larger the gap inside the bag, the higher the dry consumption of vegetables and the more oxidized. Therefore, the material should be close to the surface of the vegetables, and try to use vacuum packaging.
Frozen pea pods