Study On The Vacuum Freeze-drying And Quality Of The Bean Worm

Bean worm is a new special food and is welcomed by the vast number of consumers in recent years.It has rich nutritional and medicinal value.But,nowadays the processing and storage technology of bean worm is almost blank,which mainly by roughly cooking and frozening,thus leading to poor quality and storage period is also very short.Vacuum freeze drying technology is one of the best dehydrated method.It can retain original shape,color,etc.,and maximum nutrients.It and can also prolong the storage period of bean worm,greatly improve the processing and utilization value of bean worm.First,differential scanning calorimetry method was used in order to determin the eutectic point of bean worm,as well as the pre-freezing temperature.Secondly,single factor method was used to determin the optimum test range of bean worm.The blanching temperature and pre-freezing time were determined by freeze-dried success rate and the rehydration rate,drying chamber pressure was determined by drying time and the rehydration rate.And in the optimum range test,the measure standard of bean worm are drying time and the rehydration rate.The test was beginning by Box-Behnken experimental design and test,data was analyzed by using Design Expert 8.0.6 software.A mathematical model of the main influential factors on the rehydration rate and drying time was built in the end.Finally,the quality of bean worm in vacuum freeze drying and hot air drying was compared.The results were as follows:1.The eutectic point of bean worm is-19.9? and then the pre-freezing temperature of beam worm is-28?.2.Single factor test results show that:the best value of the blanching temperature is 60??70? and 80? respectively;the best value of the pre-freezing time is 4h?6 h and 8 h respectively;the best value of the drying chamber pressure is 31 Pa?57Pa and 85Pa respectively.3.Using Design Expert 8.0.6 software to analyze test data and built the regression mathematical model of blanching temperature(X1),pre-freezing dry time(X2)and drying chamber pressure(X3)on the rehydration rate(Y1)and drying time(Y2).By response surface analysis,the optimal parameters conditons of bean worm vacuum freeze drying:blanching temperature 65.15?,pre-freezing dry time 4h,drying chamber pressure 56.65 Pa,the predictive value of rehydration rate and drying time are 80.43%and 9.5h.According to actual situation,the following parameter were chosed:blanching temperature 65?,pre-freezing dry time of 4h,the drying chamber pressure 57 Pa,the actual measured rehydration rate is 81.29%and drying time 9.5h.4.The shrinkage rate of vacuum freeze drying is only 5%,while with the hot air drying,it is 54.92%.The rehydration rate of vacuum freeze drying is 81.29%,while with the hot air drying,it is 59.12%.The protein retention rate of vacuum freeze drying is 96.33%,while with the hot air drying,it is 77.37%.The coloration change value of vacuum freeze drying is 9.54,while with the hot air drying,it is 51.60.It is very clear through the above comparative analysis that bean worm with vacuum freeze drying can get high value and great quality than the hot air drying.