The effect of fed-batch fermentation on the production of nattokinase byBacillus subtilisLSSE-22 was investigated in shake flask and bioreactor. Glucose and soy peptone were identified as the optimal carbon source and nitrogen source through batch fermentation in shake flask, respectively. Furthermore, the effect of feeding substrate, feeding manner and feeding time on the production of nattokinase was studied on the basis of optimization of initial concentration of glucose and soy peptone. The results showed that the production of nattokinase was 1437.34 IU/mL, which was 21.38% higher than that by batch culture. In the 7.5 L bioreactor, the maximal production of nattokinase reached 2046.47 IU/mL, which was significantly higher than that by batch culture.
With adding Peruvian squid pen powder to traditional koji, this paper studied effect of squid pen powder on soy sauce koji making of spores, enzyme system and solids content change, and analyzed volatile fragrant component of soy sauce by GC-MS. The results showed that adding appropriate squid pen powder made positive effect on microbial growth and enzyme secretion. The experimental group was higher than control group in yeast concentration, spores, amylase and protease activities, solids content. The amount of squid pen powder was 1.3%。 It showed a better appearance of soy sauce koji, colour, aroma. The result of GD-MS showed that 1.3% adding squid pen powder had 36.31% volatile constituents, higher than the data 32.73% of control group, but there is no positive correlation between the amount of squid pen powder and the content of volatile.
The preparation of rice slurry is an important process in the processing of rice based fermented beverage, which has a great influence on the finished product quality. The three important processes of rice slurry preparation include: rice baking, liquefaction and saccharification were investigated by single factor experiment, and orthogonal experiments were used to optimize liquefaction and saccharification process. Results showed: the optimal baking conditions were temperature 180 ℃, time 15 min. Liquefaction conditions were 80 ℃, 140 min，thermostable α-amylase enzyme for 30 U/g. Saccharification conditions were 60 ℃, 6 h, glucoamylase dosage for 300 U/g. Under these condition, rice slurry tasted light fragrance of rice, the DE value and soluble solid content（TSS） were 99.86%, 9.4%, respectively.
o improve the quality of stirred yogurt fermented with goat milk and explore the effects of transglutaminase (TG) on the protein cross-linking degree of goat milk, stirred yogurt were treated by TG (concentrations of 1, 2, 3 u/g protein); the pH, viscosity, water holding capacity, flavor and the viable count changes in lactic acid bacteria during storage were studied and the crosslinking degree of goat milk were analyzed with SDS-PAGE electrophoresis. The results showed that the pH in storage period of yogurt was significantly higher than the control group; the viscosity and water holding capacity of stirred yogurt during storage increased significantly and the effect was more obvious with the increase of TG concentration. The contents of acetaldehyde and diacetyl decreased gradually, and the concentration of TG was greater, the effect was more obvious. TG treatment inhibited significantly the number ofStreptococcus thermophilusof stirred yogurt during storage, and with the increase of TG concentration, the content of Streptococcus thermophilus was lower, while TG treatment had no obvious effect onLactobacillus bulgaricus. SDS-PAGE revealed that the occurrence of noticeable cross-linked on kappa-casein and alpha-lactalbumin when the goat milk treated by TG, which was beneficial to the stability of yogurt gels.
The research aimed to study the fresh-cut carrots. Fresh-cut carrots were treated with NO donor sodium nitroprusside (SNP) and soaked with 0.1mmol/L by 2h. The changes of sensory qualit and physiological and biochemical indexes of 15d at 4℃ were determined. The effect of NO treatment on fresh-keeping of fresh-cut carrots were analyzed. The results showed that NO effectively reduced the occurrence rate of fresh- cut carrots.NO treatment could improve the antioxidant-related enzyme activity, such as ascorbate peroxidase (Ascorbate peroxidase, APX), catalase （Catalase, CAT). NO treatment could reduce the electrical conductivity of fresh-cut carrots’ tissue, inhibited the activity of ipoxygenase (Lipoxygenase, LOX), reduced the accumulation of malondialdehyde(Malondialdehyde, MDA), delayed the occurrence of membrane lipid peroxidation, reduced the degree damage of fresh-cut carrots’ cell membrane. NO treatment also inhibits enzymatic activities associated with phenylpropane metabolism, such as polyphenol oxidase (Polyphenol oxidase, PPO), peroxidase (Peroxidase, POD), phenylalanine ammonia lyase（Phenylalanine ammonia lyase, PAL), and the accumulation of secondary metabolites such as total phenols and flavonoids, and thus delay the process of fresh-cut carrots’ whitening.NO improves the antioxidant capacity of fresh-cut carrots and reduces the enzyme activity associated with the phenylpropane metabolic pathway to improve the sensory quality of the product and prolong the shelf life.
In the present study, the extraction efficiency of flavanones and methoxyflavones has been investigated with respect to four parameters including solvent concentration, temperature, time, and solid-liquid ratio. Water precipitation method was used to enrichment total flavonoids of sweet orange peel extract and also evaluated the antioxidant activity. Results show that the mainly flavonoids of citrus peel were flavanones and methoxyflavones; there was a significant difference between the regularity of the change in the content of the flavanones and methoxyflavones with the same extraction factor. The optimal extraction of flavanones were: 70% ethanol concentration, solid-liquid ratio of 1:20, 90℃ extraction 4 h, the content of total flavanones can reached 24.74±0.42 mg/g；the optimum condition of methoxyflavones were determined as follow: 80% ethanol concentration, and solid-liquid ratio of 1:10, 60℃ extract 2h, the yield of total methoxyflavones was 2.83±0.08 mg/g. Water precipitation method was used for enrichment sweet orange peel flavonoids extracts by removing sugars, organic acids, pigments and other impurities. After purification, the extraction yield of flavonoids was increased from 12.34% to 42.05%. 2, 2-diphenyl-1-picrylhydrazyl radicals (DPPH), and 2, 2′-azino-bis (3-ethylbenzthiozoline-6)-sulphonic acid (ABTS) methods were used to evaluate oxidation abilities demonstrated that the antioxidant capacity had highly correlated to the total content of flavonoids in the extracts.
The pickle process optimization of rutabaga is studied in this paper. Based on single factor experiment , different volume ratio of soy sauce and shrimp oil, amount of brown sugar added, CaCl2adding amount were selected to conduct a 3 factors, 3 levels central combination experiment according to the design principle of Box-Behnken experiment by establishing a quadratic regression equation for comprehensive scores of shrimp sauce pickles. Results showed that: technological factors that influenced the quality of shrimp sauce pickles according to the primary and secondary order was volume ratio of soy sauce and shrimp oil, amount of brown sugar added, CaCl2adding amount; the optimum processing technologies was that rutabaga 100 g, soy sauce and shrimp oil ratio of 3.318, brown sugar concentration 2.87% and CaCl2concentration 0.04%. The comprehensive score of shrimp sauce pickles under the condition of optimum process was 91.80 points and its relative error was about 0.1%, compared to the theoretical prediction value of 91.90. These revealed that the regression equation optimized by response surface analysis had practical guiding significance.
