From the heating point of view, microwave thawing actually heats up the frozen matter as a whole, and the temperature rises from deep freezing temperature (below-22 ℃) to near freezing point temperature (about-4℃). Therefore, microwave thawing should be microwave rewarming to be exact.
The microwave thawing of the industrial microwave thawing machine has the characteristics of the integral return temperature of the frozen material, small return temperature temperature gradient, that is, the temperature uniformity is good, the required time is short, and the temperature rise rate is easy to control and the like. The large-scale microwave thawing machine produced by the leader microwave equipment company makes the frozen material unfrozen to a more ideal state.
1.The large microwave freezer enables the frozen material to heat back as a whole, which reduces the temperature inhomogeneity between the antifreeze layers of the frozen products, and there is no recrystallizing phenomenon of the frozen products, such as that of the conventional thawing method.
2.The time required for the thawing process of the large-scale microwave thawing machine is short, and the microorganisms such as bacteria are not easy to propagate and grow. The large-scale microwave thawing machine is used to unfreeze the 4-5 cm thick frozen material, and only the time of less than 3 minutes is required at the working frequency of 2450Mhz, and the speed of the microwave thawing can be seen.
3.Large microwave freezer microwave heating has no thermal inertia. The temperature rise rate of frozen materials is controlled by microwave output power, or microwave energy supply rate, and is synchronous with each other.
4.The microwave back-temperature process of large-scale microwave thawing equipment is based on the principle of not only supplying enough energy to the material, but also balancing the energy supply rate with the energy-rate of the frozen product. No matter large or small microwave freezer, the energy supply rate and monitoring feedback are strictly controlled in the recovery process of microwave thawing machine.
Thaw refers to the soft and fresh state process before the frozen material is heated and thawed to the pre-freezing. In the domestic food factory, the thawing method of hot air or water bath is almost all used for the thawing of frozen materials. Commonly referred to as a conventional thawing method.
Conventional thawing is a conductive heating property on the surface of a material. The process is that the frozen product is melted by accepting the heat transferred by the hot medium (hot air or water) whose temperature is higher than that of the frozen product.
Disadvantages of conventional thawing:
- The normal thawing rate decreases with the progress of the thawing process, and the surface of the frozen material has been transformed into water prior to the ridging.
- The loss weight of nutrients in frozen materials is about 3% of the total weight.
- In order to avoid the surface ripening of frozen materials, the method of delaying the thawing process of frozen materials is adopted, which leads to the rapid growth and reproduction of bacteria, which affects the quality of frozen materials.
Thus it can be seen that the quality of material thawing has become an urgent problem to be solved by food science and technology workers.
European countries, such as the United States, Japan and the United Kingdom, France, Germany and Sweden, have widely used the tunnel-type industrial microwave heating and thawing equipment to heat the whole block of frozen fish, frozen meat and frozen fruits (such as cherry, strawberry), fruit juice, cocoa, and the like.
Domestic meat, poultry, fish, eggs, fruit processing plants choose 915MH or 2450MHz. the output power is from tens of kilowatts to hundreds of kilowatts. The working state of the equipment is divided into batch and continuous large microwave freezer, which makes microwave equipment a new thawing equipment to shorten thawing time, improve product quality and reduce processing loss.