Study On The Nonvolatile Taste Compounds Of Yongxin Fermentated Radish And Pure Starter-making And Fermentation

The nonvolatile taste compounds of Yongxin fermentated radish and pure starter-making and fermentation was studied which was to know the formation mechanism of taste and to solve problems of safety. The main contents are illustrated as following:1. The nonvolatile components were studied by high-performance liquid chromatography (HPLC). Their taste impacts were evaluated by taste active values (TAVs) and equivalent umami concentration (EUC) methods. Compared with salted radish, Yongxin fermentated radish was high in contents of carbohydrate, crude protein and crude fat. Glucose, xylose and fructose were detected in fermentated radish and total amounts of sugars were 148.95 mg/g. The total free amino acids content of fermentated radish was 22.42 mg/g and monosodium glutamate (MSG)-like components was high (8.11 mg/g). The contents of flavor 5'-nucleotides were also high in fermentated radish (105.47 mg/100 g). Glucose, xylose, glutamic acid, aspartic acid and disodium 5'-guanosine monophosphate (GMP) were of high TAVs (greater than one), and they had strong taste impacts on the flavour of fermentated radish. The EUC was 116.81 gMSG/100 g fermentated radish.2. We used one Aspergillus oryzae strain which was separated from rice Qu to make pure culture starter. Based on monofactorial experiment, the important factors influencing enzyme activity of glucoamylase, which identified by initial screening method of Plaekett-Burman, were temperature, time and water regain. Box-Behnken design and response surface analysis were adopted to further investigate the mutual interaction between the variables and identify optimal values that bring maximum enzyme activity of glucoamylase. Experiental results showed that temperature, time and water regain all had significant influence on the enzyme activity of glucoamylase. The optimal conditions were: temperature 35.33℃, time 3.7 d and water regain 50%, the optimal enzyme activity of glucoamylase was 2140.49 U/g. After five verification tests, the maximum predicted value was consistent with mean value of verification test. Compared with orthodox technology of Starter-Making, the time of Starter -Making was decreased 4 d, the enzyme activity of glucoamylase increased 40% at optimized condition. 3. Based on monofactorial experiment, three levels of four factors orthogonal experiment was designed. The relationships between the ratio of brine and material, time, brine concentration and temperature were researched experimentally. The optimal process levels of these four factors which were: the ratio of brine and material 1.5:1, time 96 h, brine concentration 10%, temperature 45℃.The verification tests showed that the content of reducing sugar (251.7 mg/g) in pure fermentation was higher than that (213.3 mg/g) in traditional fermentation. Compared with traditional fermentation, pure fermentation was slightly lower in Sensory Qualities, but the pure fermentation has high safety which the traditional fermentation could not ensure. The salt content in traditional fermentation (10.3%) was higher than that in pure fermentation (5.6%). The pure fermentation was low in salt content which was suitable for people's healthy.