First, the effect of cooling medium temperature. Under […]
First, the effect of cooling medium temperature. Under the process conditions of IQF Freezing Machine , the lower the temperature of the cooling medium, the faster the product freezes under the same conditions. At present, according to the specific situation in China, most of the ammonia is used as a refrigerant, and the evaporation temperature is generally selected between -35 and -45 °C. Under the IQF process, if a forced air continuous freeze is used, the temperature of the cooling medium is also related to the frosting speed of the evaporator. That is, when the evaporating frost layer reaches a certain thickness, the temperature of the cooling medium is correspondingly increased due to a decrease in the heat transfer effect. Therefore, in order to ensure the quality of the frozen, it should be done in time to defrost.
Second, the effect of air flow rate
Under the IQF Freezing process, the air flow rate is the main factor affecting the value of the exothermic coefficient. Therefore, an appropriate increase in the air flow rate can increase the degree of freezing end. For example, the common green beans freeze in the static air of -30°C, which takes about 2 hours. At the same temperature, the air flow rate increases to 4.5-5 m/s, and the freezing time is only 10 minutes.
Under certain conditions, the change between the freezing speed and the air flow rate is not linear, so the air flow rate should be comprehensively determined from an economic point of view.
Third, the effect of freezing termination temperature
The freezing termination temperature is lower than the storage temperature (-18 ° C), which is beneficial to maintain the structure under rapid freezing. If the freezing termination temperature is higher than -18 °C, the unfrozen water inside the vegetable tissue will generate large ice crystals, which will result in the destruction of the tissue structure and the increase of juice loss during thawing, which will affect the nutritional value and flavor of the product. If you are interested in learning more about freezing IQF, please click gf-machine