Research On Quality Change And Shelf Life Prediction Model Of Hongfang Fermented Bean Curd During Storage

Fermented bean curd is one of the main fermented soybean products with traditional characteristics in China,which is very popular with consumers.In the production and storage process of fermented bean curd,it is easy to produce biogenic amines.Biogenic amines are a kind of nitrogenous compound with toxicological effects.High doses can damage health and even endanger life.In recent years,with the enhancement of consumer health consciousness,people have paid more attention to the quality and safety of fermented bean curd.However,because of the incomplete cold chain system of storage and transportation,it is easy to provide conditions for microbial reproduction and biogenic amines biosynthesis,resulting in spoiling,unstable product quality and uneven shelf life.Therefore,in order to explore the quality change and shelf life prediction model of fermented bean curd during storage periods,the following three aspects were studied:(1)Determined the optimal ultrasound-assisted perchloric acid extraction conditions(extraction temperature 50?,extraction power 50w,extraction time 20 min).With dansyl chloride as the derivative agent,we determined the types and contents of biogenic amines in commercially available red bean curd by HPLC.The method was convenient,rapid and accurate.Six biogenic amines derivatives were isolated within 30 minutes,and the separation effect and linear relationship were good.The recovery rate was 89.06%? 96.21%,and the RSD of precision and reproducibility was less than 3%.Four biogenic amines were detected in red bean curd,including putrescine,cadaverine,tyramine and histamine.The content of putrescine and cadaverine was higher,and the content of tyramine was lower.PCA analysis showed that the biogenic amines content of fermented bean curd stored at low temperature was significantly different from that at room temperature or high temperature.(2)Fermented bean curd was stored at different temperatures(4?,25?,37?),and the changes of each index were significant.With the increase of the storage temperature and the extension of the storage period,the sensory quality of the fermented bean curd changed:the surface color was oxidized and dull,and the smell was obvious peculiar.The total acid content and the aerobic plate count were increasing.The moisture content did not change significantly.The content of amino acid nitrogen and water-soluble protein increased significantly at high storage temperature.The response values of electronic nose of fermented bean curd at different storage temperatures were also significantly different by LDA method.During the storage period,the coliforms of fermented bean curd were all less than 30 MPN/100g,which indicated that samples were not contaminated by coliforms.The sensory score,total acid content and aerobic plate count were significantly correlated with each other(P<0.01).In addition,they were all significantly correlated with the storage periods(P<0.01).Temperature had a significant effect on the quality of fermented.Low storage temperature was beneficial to maintain the stability of products.(3)Pearson correlation analysis showed that total acid and tyramine had the highest correlation with sensory score among the quality indexes of fermented bean curd,and total acid was in line with the first-order kinetic model,while tyramine was in line with the zero-order kinetic model.The shelf life prediction model of red bean curd was established by combining the Arrhenius equation,and the activation energy Ea in the total acid and tyramine prediction models were 45978.63 KJ/mol and 48364.86 KJ/mol,respectively.The pre-index factor K0 were 856834.45 and 16535166.93,respectively.The results of model verification showed that the relative error between the predicted value and the actual value is less than 10%,and the model prediction was reliable.The shelf life of fermented bean curd could be predicted according to the total acid and tyramine.In this paper,HPLC was used to determine the types and content of biogenic amines in red bean curd sold in Xi'an.The effects of different storage conditions on the quality and biogenic amines content of fermented bean curd were studied.The correlation between sensory score,microbial index,physicochemical index and biogenic amines content was analyzed.Key indexes were screened,and the shelf life model of fermented bean curd was constructed by combining kinetic equation and Arrhenius equation.It provided some research basis for reasonable storage and quality control of fermented bean curd.