Study On Koji-Making Process Of Soy Sauce With Multi-Strain And Its Impact On Soy Sauce Flavor

Soy sauce koji-making is one of the key links in the soy sauce brewing process. Not only does the quality of koji directly determine the formation rate of amino acid and the utilization rate of total nitrogen, but also it affects formation of the soy sauce volatile flavour compounds. Chinese soy sauce industry generally uses AS3.042Aspergillus oryzae as the main strains in the process of koji-making. This species has some good characteristics, such as fast growth rate, large amount production of spore, rich enzyme system,non-toxigenic amd so on. However, compared to the multi-strain koji-making, the enzyme of the single-strain koji is poor, so it can not fully break down raw materials of protein and starch. Due to the above causes, the utilization rate of total nitrogen is low, and the product flavor is not enough.Considering the above defects of the single-strain koji-making fermentation, the study uses that AS3.042Aspergillus oryzae respectively mixes with AS3.350Aspergillus Nige, AS3.972Monascus and Rhizopus chinensis to make koji, the main contents and conclusions are as follows:1Study on the influence of enzyme activity in multi-strain separate koji-making. The coditions of respective single-strain koji-making:using Aspergillus oryzae, Aspergillus Niger, Rhizopus chinensis and Monascus as strains, soybean meal, wheat bran as raw material, temperature:33℃. The results show that:in the42h soy sauce koji of Aspergillus oryzae, the neutral protease vitality is3030u/g, the activity of acid protease and glucoamylase enzyme respectively is457u/g,860u/g; in the48h Aspergillus Niger soy sauce koji, the neutral, acid protease activity respectively is1536.59u/g and679u/g, the glucoamylase enzyme activity is589.91u/g; in the48h soy sauce koji of Rhizopus chinensis, the activity of neutral, acid protease and the glucoamylase enzyme respectively is1536.59u/g,679u/g and1084u/g; in the48h soy sauce koji oi Monascus, the neutral,acid protease vitality and the glucoamylase enzyme activity respectively is1272.59u/g,457.18u/g and589.91u/g. Aspergillus Niger koji-making can better make up the activity weak defects of Aspergillus oryzae acid protease and glucoamylase enzyme.2Comparison of technology with multi-strain koji-making and single-strain koji-making. In the3:lmixed soy sauce koji of Aspergillus oryzae and Aspergillus Niger, the activity of neutral, acid protease and the glucoamylase enzyme respectively is1865u/g,615u/g and950u/g;42h Aspergillus oryzae soy sauce koji and48h Aspergillus Niger soy sauce koji are mixed with a3-1mix ratio, in the mixed soy sauce koji, neutral, acid protease activity and the glucoamylase enzyme activity respectively is2284u/g,648u/g and1046u/g. In conclusion, the single-strain koji-making technology, its activity of mixed koji is higher.3Using electrophoresis to study differences of enzymes. TCA/acetone precipitation is used for extraction and purification, SDS-PAGE is used to obtain extracellular enzyme spectrum. The study found that:in Aspergillus oryzae soy sauce koji, enzyme content is abundant at the molecular weight of about25kD,30kD,50kD; in Aspergillus Niger soy sauce koji, enzyme content is abundant at the molecular weight of about20kD,45kD. When determining the best end time of koji-making, the time is consistent with electrophoresis method and enzyme activity method. Comparision of enzyme activity and types of the1day koji (28-32h) and the2day koji (36-42h). The result shows that no matter determination of the enzyme activity or electrophoresis analysis, comparison on enzyme activity, enzyme system of the richness and content of extracellular protein, the2day koji is better.4The influence of mixed koji-making on physical and chemical index of soy sauce. This study examines three technology of mixed fermentation:(1) Aspergillus oryzae single koji-making fermentation (2) Aspergillus oryzae soy sauce koji and Aspergillus Niger soy are mixed with a3-1mix ratio (3) adding8%the red yeast rice in the fermentation period. It turned out that:in (1) technology, formation rate of amino acid and the utilization rate of total nitrogen is40%,53%; compared with (1) technology, formation rate of amino acid and the utilization rate of total nitrogen are separately increased by25%,15.28%in (2) technology and5%,3.64%in (3) technology. Especially in (3) technology, red index was raised from5.04to6.07. Therefore, mixed koji-making can effectively improve the utilization ratio of raw material and adding red yeast rice can enhance the colour and lustre of the soy sauce.5GC/MS of soy sauce koji-making. With HS-SPME-GC/MS extraction, using3-Octanol as internal standard, determination of soy sauce volatile flavor component type and content through the qualitative and quantitative. It turned out that:66kinds of flavor substances are detected in Aspergillus oryzae single koji-making fermentation, the content of Alcohols, phenols and heterocyclic compound separately is raisee to1.74ug/L,629.7ug/L in the20th day soy sauce. Aspergillus oryzae and Aspergillus Niger mixed fermentation, the content of Alcohols, phenols and heterocyclic compound separately is1529.07ug/L,21.09ug/L,7.39ug/L in the25th day soy sauce,94kinds of flavor substances are detected. Adding the red yeast rice technology, the content of Alcohols, phenols and heterocyclic compound separately is92.43ug/L,12.03ug/L,0.78ug/L in the20th day soy sauce. Above data shows that mixed koji-making will be able to enrich soy sauce flavor composition, improve content of soy sauce characteristic flavor.