New field of microwave sterilization technology - extended shelf life lactone tofu
Microwave sterilization , preservation is the use of the thermal effects of electromagnetic waves and biological effects under the action of the result . Mainly from the thermal effects of microwave sterilization rapid warming , rather than thermal effects of the use of microbial protein in vivo and physiologically active substances mutate, and loss of vitality or death. Therefore , microwave sterilization temperature lower than conventional methods . Conventional methods sterilization temperature to 100 degrees or more , the time to ten minutes to tens of minutes , while the microwave sterilization temperature is only between 70 to 90 degrees , for about a few minutes .
Deterioration is mainly to make soy protein in tofu bacterial decomposition of corruption sake.
There are two main metamorphic tofu reasons: First, the external bacteria stain , expressed as tofu surface sticky , smelly , common in unpackaged bare soy ; Another reason is that the process of pulp or container failed to get the bacteria or kill spores , bacterial growth in an environment suitable for breeding , causing a deterioration of soybean , common in packaged boxed lactone tofu .
In boxed lactone bean for example, to allow the condensation of the lactone tofu coagulant is added and the lactone has been heat sealed tank immersed in liquid milk to stay for about 20 minutes, but does not guarantee that kill bacteria and box spores. Because the tank water temperature is high, but the boxed tofu inside center and sterilization can not immediately reach the desired temperature ; secondly , tofu stay sink quite a long time , but the tofu center than the total time to achieve sterilization immersion total time is much shorter .
From boxed tofu sterilization temperature and time point of view, the center position of the surface to be later than that conventional water bath method of sterilization is not integrity , is not the same layered , often resulting in sterilization is not complete .
Microwave sterilization technique avoids the above-mentioned drawbacks. Because the microwave can penetrate into the heat of bean curd into the internal and external surface of the heating temperature was raised , and then curd achieve sterilization temperature while the inner and outer environments , such sterilization environment while , i.e. consistency favor complete sterilization and process control .
China Agricultural University, after years of research and test , design a set of operational processes and equipment , has enabled boxed lactone tofu fresh at room temperature for 3-5 days . According to the laboratory test data indicate that the test limit : 15 days storage at room temperature , the total number of 50 to 150 bacteria / g Coliforms 30 ~ 90 /100 grams. Have normal color, flavor , not sour , not sticky, no mildew .