How is ice cream produced by refrigeration equipment
Ice cream is a frozen dairy product. Its physical structure is a complex physical and chemical system. Air bubbles are dispersed in a continuous liquid with ice crystal. The liquid contains fat particles, milk protein, insoluble salt, lactose crystal, gum stabilizer and sucrose, lactose, soluble salt, such three-phase system composed of gas, liquid and solid phase. It can be seen as follows A partially frothy foam containing 40%-50% volume air.
The function of refrigeration equipment
The production process of ice cream mainly includes the inspection of raw materials, mixing and sterilization of ingredients, homogenization, cooling and aging, freezing, molding and filling, quick freezing, hardening and storage. These processes must be completed in accordance with certain technical conditions, otherwise, the products of good quality cannot be produced. We know that refrigeration equipment plays a crucial role in the production and storage of ice cream. But what kind of process need refrigeration equipment and what requirements do each process have for refrigeration equipment?
Cooling and aging
Aging is to refrigerate the mixture at a low temperature of 2-4 ℃ for a certain time, which is called "mature" or "ripening". The essence of the method is the hydration of fat, protein and stabilizer. The stability can absorb water sufficiently to increase the viscosity of the material liquid, which is beneficial to the increase of expansion rate during freezing and mixing. The aging time is related to the temperature of the liquid, the composition of raw materials and the variety of stabilizer. Generally, it takes 4-24 hours at 2-4 ℃. Attention should be paid to avoid contamination of impurities during aging. The aging cylinder must be sterilized and sterilized in advance to ensure the hygienic quality of the product.
The microstructure of ice cream
The freezing process is to freeze the mixture under forced stirring, so that the air is evenly distributed in all mixtures in extremely small bubble state. A part of water becomes the micro crystallization of ice. The ice cream mixture is affected by the refrigerant and the temperature decreases, the viscosity increases, and the thickness gradually becomes semi-solid state, that is, the freezing state; because of the continuous mixing and cooling of the mixer, The air gradually mixed in the freezing time and space, which makes the volume expand, and makes the ice cream reach a beautiful organization and perfect shape. The freezing temperature is -2-4 ℃, the freezing time of intermittent coagulator is 15-20 minutes, the discharging temperature of ice cream is generally -3-5 ℃, the inlet and outlet of continuous coagulator is continuous, the ice cream discharge temperature is about-5-6 ℃, and the expansion rate must be checked frequently for continuous freezing, so as to control the proper inlet and outlet and mixed air.
Quick freezing, hardening and storage
The frozen ice cream is soft ice cream without hardening. If it is poured into the container and then hardened, it will become hard ice cream. The former has more shops on the spot, while the latter has a large output.
The purpose of quick freezing and hardening is to freeze the ice cream (-3-5 ℃) from the freezing machine at low temperature (-23 ℃) quickly, to fix the tissue state of ice cream, and to complete the formation of very small ice crystal process in ice cream, so as to maintain the proper hardness of the structure, ensure the quality of ice cream, and facilitate the sale and storage and transportation. The quick freezing storage (-23~-25 ℃) or the tunnel (-35~-40 ℃) can be used for quick freezing and hardening.
Generally, the hardening time is 10-12h in the quick freezing training. If the tunnel is adopted, it will be much shorter, only 30-50 points will be required. The factors influencing hardening include the shape and size of the packaging container, the temperature of the quick freezing chamber and the circulation state of the air, the position of the indoor products, the composition and expansion rate of ice cream. Ice cream products after hardening shall be stored in low temperature refrigerators before sale, with storage temperature of -20 ℃.