Study On Vacuum Packaging Technology And Shelf Life Prediction Model Of Sweet Corn

Sweet corn has been favored by more and more consumers because of rich nutrition and delicious flavor.The deterioration of sensory quality and the loss of nutritional components during storage,transportation and sales will directly affect the edible and sales value of products.Vacuum packaging technology is the key to improving its storage quality and prolonging its shelf life.On the basis of discussing the mechanism of quality change of sweet corn,the key indexes that can characterize the deterioration of this product were determined.According to the comparison and analysis of the changing trend of key indexes of vacuum-packed sweet corn during storage under different material thicknesses and sterilization time,the optimum thickness of vacuum packaging bag and the optimum time of high-pressure steam sterilization were determined.The relationship between product quality and the storage temperature was discussed through constant temperature accelerated tests,and the shelf life prediction model of products was established.Gompertz model was used to fit the growth dynamics of microorganisms in vacuum-packed sweet corn during storage,and the growth dynamics models of microorganisms at different temperatures were obtained.On this basis,the shelf life prediction model was established.The main research contents are as follows:(1)Taking sweet corn as the research object,it is vacuum packed with a vacuumizing time of 20 s,sealing time of 1.2 s and sealing cooling time of 1.8 s.Different material thicknesses and sterilization times were selected to study the quality changes of vacuum-packed sweet corn.It was found that the sensory and nutritional quality of sweet corn packaged in a 120 μm vacuum bag and sterilized for 10 min after storage at 23℃ for 49 days was better than other treatment groups.Considering the changes of various indexes during storage,120 μm vacuum bag and sterilization for 10 min can slow down the browning degree of corn kernels.It also can keep the contents of ascorbic acid and soluble sugar at a relatively high level,thus effectively maintaining the original edible quality and appearance quality of sweet corn.(2)On the basis of the mechanism of quality change of sweet corn,the key indexes used to evaluate the quality of vacuum-packed sweet corn were determined as color,hardness,soluble protein,soluble sugar and ascorbic acid.On this basis,the quality change rules of vacuum-packed sweet corn at 23℃,33℃ and 43℃ were studied.The results showed that with the extension of storage time,the kernel of sweet corn browned,the kernel hardness increased,the soluble protein content of sweet corn increased at first and then decreased,and the soluble sugar and ascorbic acid content decreased with the extension of storage time.With the increase in storage temperature,the change rate of soluble protein,soluble sugar and ascorbic acid increased correspondingly.At 23℃,the nutrients such as soluble protein,soluble sugar and ascorbic acid decreased slowly.After 80 days of storage,the color difference of sweet corn was0.8,water content was 74.8 g/100 g,ascorbic acid was 15 mg/100 g,the soluble protein was4.3 mg/g,soluble sugar was 51 mg/g and soluble solids was 10%,which were all better than those at 33℃ and 43℃.It can be seen that the control of ambient temperature is very important in the storage process.Low temperature can effectively keep the nutritional components of sweet corn.It is suggested that vacuum-packed sweet corn should be stored in a cool and lowtemperature environment.On the basis of Arrhenius’ theory,a shelf life prediction model was established based on the color change of sweet corn,and the predicted shelf life of vacuumpacked sweet corn at 20℃ was about 252 days.(3)The quantity changes of microorganisms in vacuum-packed sweet corn during storage at 23℃,33℃ and 43℃ were measured,and the growth dynamics was fitted by the Gompertz model,and the growth dynamics models of microorganisms at different temperatures were obtained,which could well fit the growth of microorganisms in vacuum-packed sweet corn.In addition,the quadratic model of microbial growth was obtained by using the square root model,and the fitting results showed that the quadratic model can well describe the relationship between temperature,maximum specific growth rate and delay period.Finally,the shelf life prediction model of vacuum-packed sweet corn at 23℃ ～ 43℃ was established.