| Pixian broad bean paste(PXBP)is an indispensable condiment in Sichuan cuisine,known as the soul of Sichuan cuisine.At present,PXBP is still dominated by traditional fermentation,and its salt content is generally high,up to 17%-22%.On the one hand,high salt environment will lead to a variety of salt tolerant microorganisms and enzyme activities decreased,making the fermentation cycle longer.On the other hand,long-term excessive salt intake will lead to cardiovascular disease and hypertension and other diseases.However,the existing domestic researches on PXBP mainly focus on the analysis of volatile components and the dynamic changes of microbial community.Although reducing the salt content of traditional PXBP has attracted the attention of relevant researchers,the research on sodium reduction of PXBP is relatively less.How to reduce the amount of salt while ensuring the pure flavor of PXBP is one of the key points in the modernization of traditional PXBP.In this study,salt substitutes,Nisin,and their combination were applied to PXBP to explore the effect of low sodium fermentation on the quality of PXBP fermentation process,in order to develop a low sodium and pure flavor PXBP.The main findings are as follows:(1)The effects of salt substitutes on the fermentation quality of PXBP were studied.Taking Na Cl 42.8%,sodium gluconate 3.5%,KCl 45.2%,L-histidine 1.5%,L-lysine 7.0% as salt substitutes,the effects of 10%,12% and 15% on physicochemical,hygienic and sensory quality of PXBP were investigated.The results showed that the change trend of physicochemical indexes in the three groups of low salt treatment group was similar to that of PXBP with 17% traditional salt in the control group.With the extension of fermentation time,the water content and pH gradually decreased,while the content of total acid and amino acid nitrogen gradually increased.It was found that the total acid content of PXBP with 10%addition was the highest during the fermentation process,and the sensory was accompanied by obvious sour and moldy taste.The highest total number of colonies was detected at the end of fermentation,which was significantly different from the other three groups(P < 0.05).On the contrary,the quality of PXBP prepared with 15% salt substitute was the best,and the salty property was significantly lower than that of traditional PXBP(P < 0.05),and the actual content of Na Cl was 55.59% lower than that of traditional PXBP.(2)Taking PXBP fermented with 17% salt as the control,the salt content was directly reduced to 10%,12% and 15%,and each group was added with 0.10 g/kg and 0.15 g/kg Nisin(based on the quality of rehydrated bean),respectively.The results showed that,compared with the control group,when the salt content was 10%,the PXBP prepared by adding 0.10g/kg Nisin could promote the formation of amino acid nitrogen in the low salinity environment,but the total acid content reached 2.17 g/100 g at the end of fermentation,which exceeded the national standard.At the same time,the highest total bacterial count was detected at the end of fermentation.The results also showed that under the premise of minimizing the salt content and ensuring the safety,when the salt content was 15%,adding0.15 g/kg Nisin synergistically made the sauce fermented sauce system reach the suitable environment for microbial growth.At this time,the quality of low sodium PXBP was better,and the actual content of Na Cl was 11.76% lower than that of traditional PXBP.(3)The effects of salt substitutes and Nisin on the quality of PXBP during fermentation were studied.On the basis of 15% salt substitute,0.10 g/kg and 0.15 g/kg Nisin were added respectively.The results showed that compared with PXBP with 17% salt,0.15 g/kg Nisin made the acidity in the sauce system controlled to a certain extent,and the product did not produce sour and musty taste.At the same time,the addition of 15% salt substitutes increased the formation rate of amino acid nitrogen and the consumption rate of reducing sugar,which was conducive to the formation of flavor.Therefore,the quality of PXBP was better when the addition of salt substitutes was 15% and Nisin was 0.15 g/kg,and the actual content of Na Cl was 55.59% lower than that of traditional PXBP.(4)Taking the traditional PXBP fermented with 17% salt as a control,comprehensively compared the differences in the physicochemical,hygienic,sensory and flavor qualities of the PXBP prepared by salt substitute,Nisin,the combination of salt substitute and Nisin in the fermentation process of the low-sodium PXBP.The results showed that,compared with the other three samples,PXBP prepared by the compound group was not only conducive to the formation of amino acid nitrogen,but also promoted the metabolism of lactic acid bacteria and other microorganisms to form lactic acid and other organic acids by reducing sugar,and the total number of colonies in the compound group was significantly lower than that in the control group(P < 0.05).In the sensory aspect,PXBP prepared by the compound group was closer to the unique red brown sauce color of the control group,and the sauce flavor was richer,and the salty taste was significantly lower than that of the control group(P < 0.05).Moreover,the total free amino acid content in the product of the compound group was higher,and the total organic acid content was lower than that of the control group.In addition to aldehydes and olefins,the volatile flavor compounds in the compound group were more abundant than those in the control group,and the content of key flavor compounds in the compound group was higher than that in the control group,especially the content of phenylethanol and 4-ethylphenol was about 4 times of that in the control group.(5)Pearson correlation analysis was used to analyze the internal relationship between key flavor compounds,free amino acids and organic acids in low-sodium PXBP fermented by salt substitutes and Nisin.The results show that the correlation between aldehydes and free amino acids in key aroma compounds is strong.The taste characteristics of free amino acids have a greater impact on key aroma compounds,and the specific performance is that most of the bitter amino acids and glutamic acid with umami characteristics are negatively correlated with alcohols.The sweet amino acids and aspartic acid with umami characteristics are positively correlated with alcohols and aldehydes.Oxalic acid,succinic acid,and fumaric acid are negatively correlated with free amino acids overall,while tartaric acid,malic acid,and lactic acid are positively correlated with free amino acids overall.Among the key aroma compounds,phenylethyl alcohol,3-methylthiopropanol,furfural,phenylacetaldehyde and ethyl nonanoate showed a significant positive correlation with lactic acid. |
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