| Hakka rice wine is rich in nutrition which can adjust human physical condition and has the antioxidant and antimicrobial activity. The polyphenols is the important active substances in Hakka rice wine. Escherichia coli, Staphylococcus aureus, Salmonella are harmful bacteria parasitizing large intestine of human. Research on the antioxidant and antimicrobial activity of Hakka rice wine provides a theoretical basis for the development of Hakka yellow rice wine nutrition and hygienic value. The results of the study are as follows:(1) The components of polyphenols in Hakka rice wine were analyzed by HPLC-MS.Chlorogenic acid, rutin, p-coumaric acid, ferulic acid, syringic acid were detected.(2) Antioxidative activity of polyphenols in Hakka rice wine was measured by free radical scavenging assay(DPPH) and ferric reducing antioxidant power(FRAP). The content of polyphenols was determined by Folin CHOCAT method. The content of polyphenols in Hakka rice wine was the highest in 1 months, which was highly significant higher than in other time points(p < 0.01), and the DPPH radical scavenging ability was significantly decreased after sterilization, while the iron reduction ability was significantly increased. Effects of concentration, temperature, light and p H on the antioxidant activity of polyphenols in Hakka rice wine were studied. The correlation analysis showed the contents of polyphenols in Hakka rice wine were positively correlated with both DPPH free radical scavenging ability and iron reducing ability in different p H of the reaction system. Under the influence of temperature, the contents of polyphenols in Hakka rice wine were positively correlated with both iron reduction ability and DPPH free radical scavenging ability. Under the influence of illumination, the contents of polyphenols in Hakka rice wine were negatively correlated with both DPPH free radical scavenging ability and iron reducing ability. Therefore, the antioxidative activity of polyphenols in Hakka rice wine may be mainly determined by some kinds of phenolic substances of which the stability directly affect its antioxidant capacity.(3) The polyphenols of antimicrobial activity in Hakka rice wine on Escherichia coli,Staphylococcus aureus and Salmonella were determined by the Oxford cup assay and OD value. The minimum inhibitory concentration(MIC) of polyphenols in Hakka yellow rice wine on Escherichia coli, Staphylococcus aureus and Salmonella were 1.25 μg GAE / m L,2.51 μg /m L, and 5.02 μg GAE/m L respectively. The polyphenols in Hakka yellow ricewine had strong antimicrobial activity on these three kinds of harmful bacteria. Effects of concentration, temperature, illumination, p H, gelatin, and Fe3+ on the antibacterial activity of the polyphenols in Hakka rice wine were studied. After treated by different p H and illumination, the contents of polyphenols in Hakka rice wine were highly significantly correlated(p < 0.01, two tailed test) with antimicrobial activity on Escherichia coli. The correlativity between the contents of polyphenols in Hakka rice wine and antimicrobial activity on Escherichia coli was not significantly correlated(p < 0.05) under the effects of temperature, gelatin and Fe3+. The correlativity between the contents of polyphenols in Hakka rice wine and antimicrobial activity on both Staphylococcus aureus and Salmonella was not significant(p < 0.05) under the effects of p H, temperature, light, gelatin and Fe3+.The results showed the contents of polyphenols in Hakka rice may not be the keys to influence on its antimicrobial activity. This antimicrobial activity of polyphenols in Hakka yellow rice wine on Escherichia coli, Staphylococcus aureus, Salmonella may be determined by some kinds of components of polyphenols. These components were slightly affected by p H, temperature, light, gelatin and Fe3+. Although total polyphenol contents were changed, it would not greatly affect the antimicrobial activity against these three harmful bacteria.(4) The antibacterial mechanism of polyphenols in Hakka yellow rice wine on the Escherichia coli, Staphylococcus aureus and Salmonella was determined by electrical conductivity, alkaline phosphatase, protein, p H, and Gram stain. The antimicrobial activity of polyphenols in Hakka rice against Escherichia coli, Staphylococcus aureus, Salmonella is bacteriostat but not sterilization. The polyphenols in low concentration(Escherichia coli:1.25 μg GAE/m L, Staphylococcus aureus: 2.51 μg GAE/m L, Salmonella: 5.02 μg GAE/m L)can inhibit the growth of three species of harmful bacteria and can persistently inhibit for a long time(Escherichia coli: 32 h, Staphylococcus aureus: 48 h, Salmonella: 44 h). By means of electrical conductivity, alkaline phosphatase, protein, p H and sanning electron microscope(SEM) analysis confirmed the antimicrobial mechanisms of polyphenols in Hakka rice wine against Escherichia coli, Staphylococcus aureus, and Salmonella were based on destroying the integrity of the cell wall, increasing the permeability of the cell membrane, changing the normal metabolism, and eventually inhibit the bacterial growth. |
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