The Effects Of Different Solid Concentrations Fermentation On Physicochemical Properties And Sensory Evaluation Of High-salt And Liquid-state Soy Sauce

Soy sauce is one of the traditional fermented foods, which is also an important condiment of our Chinese and Southeast Asian, even worldwide people. China is a country of big production and consumption of soy sauce, with the annual output of about 7,000,000 tons and an annual growth rate of approximately 10%. Currently on the market, High-salt and diluted-state fermentation has become the main mode of production of high-quality, high-grade soy sauce, but it has some disadvantages such as long fermentation period and low capacity utilization. With the improvement of the concept of life, low consumption and energy as environmentally friendly production methods become the development direction of society. In recent years, due to the higher equipment utilization, less energy consumption and water waste of high solid concentrations fermentation when compared to low solid concentrations fermentation, it has become a research hotspot and now is widely used in the treatment of beer and alcoholic fermentation and so on. Still, the effect of different solid concentration on high-salt and diluted-state soy sauce has not been reported yet.This paper systematically studied the effects of different solid concentrations on high-salt and diluted-state soy sauce, including the traditional solid concentrations, 30% and 33%, and the higher ones,37% and 41%.Changes in microorganisms, antioxidant capability and the formation and release of soy sauce taste substances were comprehensively monitored during the fermentation. Meanwhile, the correlation between water activity and microorganisms as well as the differences in the aroma substance and utilization rate of protein were analyzed, and the key taste and aroma substance were identified. All of these researches were aimed to providing a theoretical basis and guidance for the application of high solid concentrations fermentation in high-salt and diluted-state soy sauce.Changes in microorganisms and the correlation between microorganisms and water activity were analyzed during different solid concentrations fermentation. With the increase the fermentation time, the total number of colonies, lactic acid bacteria, yeast and mold counts showed a downward trend, but the significance of the decrease in the total number of colonies, lactic acid bacteria and yeast differed from the fermenting solid concentrations. After 60 d fermentation by adding yeast manually, the number of yeast in higher solid concentrations soy sauces kept at 106cfu/g which was 10 times higher than traditional solid concentrations ones. Furthermore, there also was a significant or very significant positive correlation between lactic acid bacteria and water activity. When the fermenting solid concentration was lower, there was a significant negative correlation between the total number of colonies and mold counts, also there was a large negative correlation between yeast and the total number of colonies.Four kinds of soy sauces processing are the object of this dissertation. The results showed that the higher the solid concentration was, the lower the salt content in soy sauce was, which remained higher neutral protease activity. Total nitrogen, amino acid nitrogen, total acid, reducing sugar, dark matter and color ratio showed a significant increase(P<0.05) but the red and yellow index decreased in soy sauces fermented under a higher solid concentration(37% and 41%) when compared to the traditional solid concentrations ones. Furthermore, the peptides with molecular wight 1-5k Da and flavor amino acids also improved under higher solid concentration fermentation, contributing to stronger taste. Besides, the Quantitative Description Analysis(QDA) showed that the umami taste and sour were the strongest in SS1.5, while the bitterness was the weakness. Thus it could be seen that soy sauce fermented under high solid concentration efficiently improve the taste.In combination with headspace solid phase micro-extraction and direct solvent extraction, and using the GC-MS for analyzing, the results showed that there were each 114 kinds of volatile aroma substances in SS1.1 and SS1.5 while 111 kinds in SS2.0 and SS2.5. Alcohols, aldehydes, ketones, acids were the main component of volatile flavor in soy sauces. Substances other than alcohol and ketones, other aroma components showed a significant increase(P<0.05) when increasing the solid concentration. Therefore, soy sauce fermented under higher solid concentrations showed a more balanced aroma and a more prominent sour and smoked flavor but a weaker flower, mellow and burnt flavor.The differences in utilization rate of protein and changes in antioxidant capability of soy sauce under different solid concentrations fermentation were compared. Utilization of protein went up with the increase of fermenting solid concentration, the highest growth was two percentages. Comprehensively investigating from 3 indicators including DPPH radical capability, reducing power and hydroxyl radical scavenging ability, it was found that improving solid concentrations increased the antioxidant capacity of soy sauce.