Study On Preparation And Storage Stability Of Complex Jiaosu

According to Plant Enzyme(QB/T 5323-2018),the light industry standard of the People’s Republic of China,edible plant Jiaosu refers to the products that contains specific biological active ingredients and can be used for human consumption.It takes plants that can be used for food processing as the main raw materials for microbial fermentation with or without auxiliary materials.At present,the development level of edible plant Jiaosu in our country is at its primary stage,and edible plant Jiaosu have great development space and research value in our country.In particular,the complex Jiaosu based on multiple raw materials and complex strain fermentation is more in line with the current market demand.In addition,yeast and lactic acid bacteria have a synergistic effect during fermentation,and the co-fermentation technology is more conducive to improve the quality of Jiaosu products.Therefore,in this study,the Pichia kluyveri and Lactobacillus plantarum were sequentially inoculated into the mixed juice composed of banana,broccoli and wolfberry to prepare complex Jiaosu.The quality and storage stability of complex Jiaosu were comprehensively analyzed.The main research contents of this paper are as follows:1.Firstly,the co-fermentation process was determined.In brief,6.00 log CFU/m L Pichia kluyveri was inoculated into the juice and the fermentation time was 24 h,then 7.00 log CFU/m L Lactobacillus plantarum was inoculated and the co-fermentation time was 8 d.The physicochemical properties,bioactive components,antioxidant capacity and taste of complex Jiaosu were studied.The results showed that the superoxide dismutase(SOD)activity increased by 30.24 times and the content of total phenol increased by 1.07 times after co-fermentation.The contents of lactic acid,protocatechuic acid and chlorogenic acid increased,while the contents of caffeic acid and malic acid decreased.The ABTS radical scavenging ability and hydroxyl radical scavenging activity were increased by 1.93 folds and0.50 folds,respectively.The gamma-aminobutyric acid(GABA)concentration also has a significant increase during fermentation.In addition,electronic tongue analysis showed that the main taste characteristics of complex Jiaosu were sour and sweet taste.2.In order to study the influence of co-fermentation technology on flavor characteristics of complex Jiaosu,the GC-MS,ROAV and electronic nose analysis were used to systematically analyse the differences of flavor characteristics of single fermentation(Pichia kluyveri fermentation(PKF),Lactobacillus plantarum fermentation(LPF))and co-fermentation(CFLP).The results showed that 127 volatile compounds of 8 classes were identified in all samples.The total amount of esters,acids and alcohols increased significantly in all samples,while the total amount of aldehydes and ketones decreased significantly.In addition,CFLP samples had the highest level of esters and the highest overall aroma intensity.Besides,there were some new aromatic compounds(such as eugenol)during co-fermentation.The results of odor activity value(ROAV)showed that ethyl acetate,isoamyl acetate and isoamyl alcohol had the highest contribution to the flavor characteristics of CFLP samples,and the ROAV were 544.42,571.94 and 676.02,respectively.Different samples were also well distinguished in the electronic nose PCA results,and there was little difference between CFLP and LPF samples.3.The storage stability(4℃,25℃,and 37℃)of complex Jiaosu after pasteurization was studied.The p H and TA of complex Jiaosu stored at 4℃ showed the highest stability,and the p H value was 3.41 after 56 d of storage.Ascorbic acid decreased by 22.07%,30.28% and36.38% during storage.SOD activity also showed a downward trend to varying degrees,and ascorbic acid had a certain protective effect on it.The color difference ΔE and sensory scores decreased most slowly at 4℃.In addition,combined with the Arrhenius equation and zero-order kinetic reaction,the shelf life model of the complex Jiaosu was established.In addition,the shelf life of complex Jiaosu was predicted to be 184 d at room temperature.Then the shelf life model was verified at different temperatures,and the relative errors of predicted and measured values were both below 5%.Therefore,this model can accurately predict the shelf life of the complex Jiaosu.