2, collapse (disintegration) temperature The collapse t […]
2, collapse (disintegration) temperature
The collapse temperature of food is also called disintegration temperature. It refers to the temperature at the IQF Freezing and sublimation stage. As the temperature rises, the product loses its rigidity and begins to become sticky. The temperature is similar to the collapse, melting or foaming phenomenon of landslide. Collapse in the process will seriously affect the quality of the product. Therefore, it is necessary to prevent the occurrence of collapse during the IQF Freezing of the food material. The collapse is mainly related to the product process and the nature of the material itself. Different freeze-drying parameters have an impact on the occurrence of collapse.
For example, Zuo Jianguo and others used freeze-drying microscopy to study the effects of cooling rate, sublimation pressure and solution mass fraction on the collapse temperature of the dry layer during the freeze-drying process. The results show that for 10% For the sucrose/water binary solution, the cooling rate has no obvious effect on the collapse temperature; while for the 10% t-butanol/10% sucrose/water ternary solution, the collapse temperature decreases significantly with the increase of the cooling rate; the pressure versus the collapse temperature The effect is not significant; the solution mass fraction is different, and the collapse temperature slightly changes.
However, the optimization process can reduce the occurrence of collapse. Dong Huilong explored the factors affecting the collapse of papaya freeze-dried chips. The results show that the blanching pretreatment and hardening pretreatment can slow down the collapse of freeze-dried products, and the freezing rate has no effect on product quality. Large, but insufficient freezing time will cause the freeze-dried product to collapse.
The collapse temperature is also affected by the physical properties of the food material itself. Some food disintegration temperatures are higher than the eutectic point temperature. When the IQF Freezing operation is performed, the product temperature is controlled to be lower than the eutectic point temperature; some foods have a disintegration temperature lower than that. The eutectic point temperature should be closely monitored for the disintegration temperature during the IQF Freezing operation. At present, the measurement of collapse temperature is difficult and needs to be measured by means of a freeze-drying microscope. In recent years, many studies have used IQF Freezing protectants to avoid product collapse, in order to achieve energy saving and protection of product morphology. Hamoudi optimized the formulation of the freeze-dried protectant of Geotrichum candidum, and Zeng Xiaoqun optimized the Lactobacillus casei. The best formula for dry protectants.