Study On Preservation Technology Of Sweet Potato Leaves Pickles Fermented By Lactic Acid Bacteria

Lactic acid bacteria fermentation of sweet potato leaves can prolong the sweet potato industry chain and improve the added value of sweet potato by-products.After fermentation,it can not only retain the nutritional components of sweet potato leaves,but also use the function of lactic acid bacteria to increase the flavor of sweet potato leaf sauerkraut.However,the subsequent preservation process has not been studied.The preserved pickled cabbage is prone to quality problems such as corruption and deterioration,which can not form a complete product sales chain and is difficult to meet the market demand.The shelf life of fermented products is the key factor restricting their market circulation,so different preservation processes are needed to meet different supply needs.Large supermarkets with cold chain supply equipment can adopt the preservation method of pasteurization and refrigeration,small and medium-sized supermarkets without refrigeration equipment can adopt the preservation method of placing at room temperature after adding additives.The two preservation methods can meet the needs of different suppliers.In this study,the shelf life of sweet potato leaf sauerkraut under two preservation technologies was studied with fermented sweet potato leaf sauerkraut as raw materials.In the study,the key preservation steps and quality changes of sweet potato leaf sauerkraut were analyzed and studied.The specific contents are as follows:(1)The quality changes of sweet potato leaf sauerkraut after four preservation methods were analyzed,take p H value,lactic acid content,nitrite content,lactic acid bacteria number,yeast number,Escherichia coli number,total bacteria number and sensory evaluation as indicators.The results showed that the preservation quality at 4℃after sterilization at 80℃-15min was the best,and it could be preserved for 90 days under this condition.(2)It shows that some quality changes will lead to other quality changes at the same time.The contribution value of principal component is obtained through principal component analysis.The first principal component can represent the physical and chemical indexes of sauerkraut,and the second principal component mainly includes the microbial indexes of sauerkraut.(3)Through single factor screening test,the types of preservatives added were determined as follows:potassium sorbate,sodium dehydroacetate,sodium benzoate and sodium diacetate.The type and concentration range of preservatives were determined by single factor test,and the best formula of anti-corrosion compound was determined by response surface optimization test:The addition amount of potassium sorbate is 0.32g/Kg,the addition amount of sodium dehydroacetate is 0.32 g/Kg,and the addition amount of sodium benzoate is 0.34 g/Kg,the colony number of sweet potato leaf sauerkraut under this compound was 3.59902 lg(CFU/m L),the predicted value is close to the actual value after verification test.This formula can be used as the antiseptic and bacteriostatic formula of sweet potato leaf pickled cabbage.(4)By comparing the changes of color and texture of sweet potato leaf sauerkraut after adding different kinds and concentrations of color protectants,select the appropriate concentration of sodium D-isoascorbate and citric acid to carry out the response surface optimization test,and take the brightness L~*value as the response value to obtain the best color protection formula.The addition amount of sodium D-isoascorbate and citric acid was 0.17%and 0.08%,respectively.The brightness L~*value of sweet potato leaf sauerkraut was 37.8907,after the validation test,the actual value is close to the predicted value,and the formula is reliable.(5)The best anti-corrosion and color protection formula was applied to sweet potato leaf sauerkraut.By analyzing the correlation between physical and chemical indexes and sensory scores under storage at 4℃,27℃and 37℃,sensory score was selected as the key factor.The shelf-life prediction model of sweet potato leaf sauerkraut sensory quality was established by combining the first-order kinetic equation with Arrhenius equation,predict the shelf life of sweet potato leaf sauerkraut at different temperatures.The establishment of this model can accurately predict the shelf life at different storage temperatures after adding anti-corrosion and color protection agent.