Changes Of Flavor Substances And AFB1 Safety Assessment During The After-ripening Period Of Pixian Soybean Paste

As China's geography signs products,pixian soybean paste(PSP)has been a favorable option of customers with a long history as a protein source and an essential ingredient in China,especially in Sichuan province.Several steps are involved in the preparation of PSP.To manufacture PSP-meju,which called primary fermentation,broad bean(Vicia faba L.)is prepared by soaking,steaming,and subsequent mixed with wheat flour(Triticum aestivum L.)and 10-12 % w/v salt inoculated with Aspergillus oryzae for about 2-3 months.The DBJ-meju is then added upon with brine(20% w/v salt)and cut red pepper(approx.1-2 cm),and then fermented for several months or years depend on the temperature,weather,environment,flavor and taste characteristics,even marketing,called post fer mentation,which endowed with unique characteristics of the PSP.The suites of post fermentation manufacturing processes and microbial consortia significantly influence the qualitative characteristics of fermented PSP products with profound alterations in the metabolite and enzyme compositions governing their physicochemical properties.In this study,the contents of organic acid and amino acid of PSP in different fermentation periods were studied by the high performance liquid chromatography(HPLC)and 30+ amino acid automatic analyzer,respectively.And the quality characteristics and change regularity of PSP after the fermentation period were evaluated in order to provide theoretical basis for the determination of post-fermentation management.In addition,the traditional fermentation production of PSP was in a relatively rough environment which is easy to produce fungal toxins,such as aflatoxin B1(AFB1).It damages the liver of human,resulting in a disorder metabolic system.And it seriously affects people's health.So it is very vital significance to provide scientific support for the safety management and to provide reliable basis for food safety risk assessmentThe organic acid content from 1 month to 2 years were analyzed by HPLC.The results show that the optimal chromatographic conditions were determined.An Agilent Venusil MP C18(4.6mm×250mm)column was used to separate the organic acids.The mobile phase was a mixture of 0.01mol/L(NH4)2HPO4 and methanol solution at a flow rate of 0.8ml/min.The column temperature and UV detection wavelength were set as 30°and 220 nm,respectively.It was found that the organic acid content of PSP was decreased from 19.01g/kg to the lowest of 14.81g/kg.Subsequently,the organic acid content began to increase,reaching a peak of 48.79g/kg at the end of 9 months,and finally to a gradual level.The content of acetic acid,lactic acid and citric acid varied greatly at each stage.The amino acid content was measured and analyzed by 30+ amino acid automatic analyzer,and the flavor effect of different fermentation period was evaluated.The results showed that the content of amino acid nitrogen in PSP was increased with the fermentation time prolonged and then drop.The highest content was 0.422g/100 g in the 9 months after the fermentation,then decreased to 0.361 g/100 g in the first year after fermentation,and finally reached 0.375 g/100 g in the second year after fermentation,and then leveled off.The average content of 5 kinds of amino acids,respectively: Glutamic(3.06 mg/g),Proline(2.42 mg/g),Aspartic(2.05 mg/g),L-Asparagine(1.76 mg/g)and Arginine(1.15 mg/g),they accounted for the sum of 55.01% of the total amino acids of PSP.The amino acids with the greatest change in the content of the latter fermentation were Aspartic,L-Asparagine,Alanine,Lysine and Proline.They displays delicious and sweetness.The color,aroma,taste and body of PSP during different post-fermentation period can be used as one of the basis for the evaluation of the post-fermentation stage of PSP.The pollution of AFB1 in PSP from 296 batches were collected and detected from different seasons by ELSA.The results show that the average concentration of AFB1 was 3.011?g/kg and relevance rate was 94.60%.During the spring and summer season,the average concentration of the samples was 3.566?g/kg and the qualified rate was 92.74%.The average concentration of the autumn and winter seasons was 3.057?g/kg and the qualified rate was 96.47%.It can be seen from this that the production season has a significant effect on the AFB1 in PSP.