Study On The Formation And Changes Of Flavor Compounds In High-salt And Diluted-state Soy Sauce During Fermentation And Pasteurization

The present study mainly dealed with the formation and changes of flavor compouns in high-salt and diluted-state soy sauce during fermentation and pasteurization. On the basis of optimized flow chart of Koji-making and moromi fermentation of high-salt and diluted-state soy sauce. Firstly, this study focused on the formation and changes of taste and aroma compounds in high-salt and diluted-state soy sauce during fermentation and pasteurization, and the impact of soybean oil on the formation of aroma compounds in high-salt and diluted-state soy sauce. Finally, the taste-active and aroma-active compounds in high-salt and diluted-state soy sauce were identified, respectively.On the basis of technologies of modern bioproccess optimization, i.e., Box-Behnken et al, the processings of Kojis prepared using A. oryzae 3042 and A. niger 3.350, respectively, were optimised, and the rates of protein utilization and amino acids conversion were increased by adjusting the proportion of Kojis prepared using A. oryzae 3042 and A. niger 3.350 to balance the distribution of enzymes in the mixed Kojis. The optimal processing conditions of Koji-making of A. oryzae 3042 and A. niger 3.350 were as follows. Soybean steaming time: 13.3 min and 13.8 min, soybean steaming temperature: 120°C and 120°C, Koji culture time: 44.5 and 49.2 h, Koji culture temperature: 28.5°C and 28.5°C. The enzymes acitivities of A. oryzae 3042 (neutral protease) and A. niger 3.350 (acid protease) reached to 1395.00±124.40 U/g and 1885.67±160.05 U/g under the optimal conditions, respectively, which were increased by 2.33% and 5.10% when compared with those in Kojis prepared under their optimal conditions of single factor design. The optimal processing conditions of fermentation were as follows. Koji culture temperature and time: 38.8°C and 34 d, the ratio (w/w) of Kojis parepared with A. oryzae 3042 and A. niger 3.350: 3:1. The contents of formaldehyde nitrogen and total nitrogen reached to 0.97±0.05 g/100mL and 1.65±0.08 g/100g under the opitmal conditions, respectively, which were increased by 3.19% and 4.30% when compared with those in fermentation liquids prepared under their optimal conditions of single factor design.The taste and aroma compounds profiles in high-salt and diluted-state soy sauce during fermentation and pasteurization were established by modern chromatagraphy methods, then the relationships between taste and aroma compounds and results of quantitative descriptive analysis were delineated by cluster analysis (CA). Furthermore, the taste-active and aroma-active compounds in high-salt and dilute-state soy sauce were identified, the results would greatly benefit to targetedly adjust the taste and aroma in high-salt and diluted-state soy sauce. The results indicated formaldehyde nitrogen, total nitrogen, reducing sugar, water soluble peptides and free amino acids were sharply released in the earlier fermentation stage (30 d), whereas Maillard reaction products were sharply formed during pasteurization. Furthermore, the studies revealed that the harmoniously interaction of the 17 amino acids (excluding cystein) played a key role in the taste formation of high-salt and diluted soy sauce. Meanwhile, the peptides with molecular wight 1～5 kDa and Maillard reaction products played an active role as well. Most aroma compounds of high-salt and dilute-state soy sauce were proved to exist in the earlier fermentation stage by GC-MS analysis and QDA, whereas the good aroma of high-salt and dilute-state soy sauce was formed in the late fermentation stage (120 d). Meanwhile, only slight effect of pasteurization on the aroma of high-salt and dilute-state soy sauce was observed. The aroma-active compounds in high-salt and diluted-state soy sauce were identified by GC-MS analysis combining with QDA and CA, which were listed as follows: acetic acid, butyric acid, 3-metyl, butyric acid, 2-metyl-, benzoic acid, phenylacetic acid, ethanol, propanol, 2-methyl-, 1-octen-3-ol, phenylethanol, butanal, 3-methyl-, butanal, 2-methyl-, benzaldehyde, Benzeneacetaldehyde, furfural, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2-ethyl-4-hydroxy-5-methyl-3(3H)-furanone, pyrroline, 2-acetyl-, phenol, 2-methoxy-, 2-methoxy-vinylphenol, 2-methyl-3-methoxy-4H-pyran-4-one, pyrazine, 2,6-dimethyl-, propanal, 3-(methylthio)-, propanol, 3-(methylthio)-.The impact of soybean oil on the aroma and sensory attributes of high-salt and diluted-state soy sauce was elucidated by combinating GC-MS analysis and QDA, CA. The results clarified content of soybean oil in moromi significantly affected the aroma of high-salt and diluted-state soy sauce. The higher content of soybean oil in the moromi to a certain extent, the higer contents of acids, alcohols, aldehydes/ketones and esters in high-salt and diluted-state soy sauce were determined. Meanwhile, the higher ratio of defatted soy meal Koji used in moromi, the higher content of sulfur-containing compounds in high-salt and diluted-state soy sauce was determined. Furthermore, the optimal ratio 1:1 of Kojis prepared using soybean and defatted soy meal was established, and the aroma of high-salt and diluted-state soy sauce prepared using mixied Kojis (soybean Koji : defatted soy meal Koji = 1:1) was not affected. It was worthy to mention that the production cost of high-salt and diluted-state soy sauce prepared using mixed Kojis (soybean Koji : defatted soy meal Koji = 1:1) could be markedly lowered.