Studies On Antioxidant And Bacteriostatic Activities Of Fermented Soybean Wheys

Tofu wheys are the industrial wastewater generated in the process of manufacturing tofu,which have a large yield, and contain oligosaccharides, proteins, isoflavones and other richnutrients. If tofu wheys are discharged directly, which will seriously pollute the environment,and cause great waste of resources. Lactobacillus is widely used in the food industry, whichnot only can improve the flavor and nutritional value of food, but also regulate the intestinalflora, aid in disease prevention. In the paper, we used tofu wheys as lactic acid fermentationsubstrate, and studied the changes of antioxidant and antibacterial activity of fermented tofuwheys by lactic acid bacteria, laid the foundation for the further development and utilizationof tofu wheys.The research discussed the antioxidant properities of unfermented and fermented tofuwheys. The antioxidant activities were examined by ferric reducing antioxidant power,scavenging effect on DPPH and ABTS, and chelating effect on ferrous. The results indicatedthat the tofu whey fermented by Lactobacillus acidophilus had the strongest reducing poweramong the tofu whey fermented by Lactobacillus rhamnosus and the tofu whey itself. Thefermented tofu whey had stronger scavenging effect on DPPH and ABTS than unfermentedsoybean whey, but there were no significant difference between strains and fermentation time.The order of chelating effect on ferrous was followed by: tofu whey fermented byLactobacillus rhamnosus> tofu whey fermented by Lactobacillus acidophilus> unfermentedtofu wheys, and the chelating power could be improved significantly by extendingfermentation time. This research confirmed that both unfermented and fermented tofu wheyall had antioxidant activities, which provided a new direction for further using of tofu whey.The lactose and sucrose were chosen as carbon source and added to tofu whey, afterfermentation by Lactobacillus acidophilus and Lactobacillus rhamnosus respectively, theeffect of different carbon sources and their additive amount on the produce of acid ability, theantioxidant and bacteriostatic activity of them were investigated. The results indicated that:(1)The addition of sucrose was able to improve the production of acid in the fermentation course,the titratable acidity of soy bean whey with5%sucrose fermented by Lactobacillusacidophilus and Lactobacillus rhamnosus for24h reached95.80oT and93.68oT;(2) The addition of sucrose was able to increase the antioxidant activities of fermented soy bean whey,after fermentation for48h by Lactobacillus acidophilus and Lactobacillus rhamnosus, withthe addition of5%sucrose, the power of reducing was2.57and2.47mM Trolox/mlfermented soy bean whey, the scavenging ABTS was37.69and37.98mM Trolox/mlfermented soy bean whey, and chelating ferrous was75.69%and78.70%respectively;(3)Moreover, the soy bean whey fermented by Lactobacillus acidophilus and Lactobacillusrhamnosus for24h had inhibitory effect on the growth of staphylococcus aureus andEscherichia coli, but no inhibitory effect on bacillus cereus with the cylinder-plate method,the bacteriostatic activity of soy bean whey fermented by Lactobacillus acidophilus wasmuch stronger than that by Lactobacillus rhamnosus, while the activities of the fermented soybean whey only increased slightly with the addition of1%sucrose.The effect of garlic essential oil on the produce of acid ability, the antioxidant andbacteriostatic activity of fermented tofu wheys by Lactobacillus rhamnosus and Lactobacillusacidophilus were investigated. The results indicated that adding the low concentration ofgarlic essential oil to tofu wheys had no significant effect on the growth and acid productioncapacity, and the total number of lactic acid bacteria reached107cfu/mL, titratable acidityvalue reached80~90oT. The addtion of garlic essential oil was able to increase the capacityof reducing ferric, scavenging DPPH and ABTS, and chelating ferrous.The higherconcentration of garlic essential oil could improve the capacity of reducing ferric andscavenging ABTS. Moreover, adding garlic essential oil to tofu wheys could inhibit growth ofbacillus cereus, the number of bacillus cereus detectived was less than10cfu/mL.