Antimicrobial Activity of Tea Polyphenols and Its Application in Fruit Compound Preservative

Because tea polyphenols had the characteristics of anti-oxidation, bacteriostasis and environmental protection, an efficient natural fruit compound preservative containing tea polyphenols was developed. The inhibitory concentration of tea polyphenols was determined by comparing the antibacterial effects of tea polyphenols, sodium benzoate and potassium sorbate. Then, the effects of the compound preservative, containing tea polyphenols and coating agent (carnauba wax and commercial coating agent) on the preservation of Citrus reticulata were further studied. The bacteriostasis test results showed that the minimum inhibitory concentrations of tea polyphenols against Escherichiacoli, Bacillus subtilis and Staphylococcus aureus were 0.4 g·L^-1, 0.6 g·L^-1 and 1.0 g·L^-1, respectively. The antibacterial effect of tea polyphenols was significantly better than that of sodium benzoate and potassium sorbate, but it had no inhibitory effect on Saccharomyces cerevisiae. Based on the bacteriostasis test results, the concentration of tea polyphenols in the compound preservative was determined to be 0.8 g·L^-1. The preservation experimental results of Citrus reticulata showed that compared with the blank control, the treatments of commercial coating agent (CP), commercial coating agent+tea polyphenol (CP-TP), carnauba wax (ZL), carnauba wax+tea polyphenol (ZL-TP) all had the preservation effects. The hardness and water retention capacity of Citrus reticulata treated with carnauba wax were significantly higher than those treated with the commercial coating agent, and the bacteriostasis rate and vitamin C content of peel treated with carnauba wax were significantly higher than those treated with the commercial coating agent. Tea polyphenols could significantly improve the bacteriostasis rate of carnauba wax preservative, maintain the content of vitamin C and reduce the respiration rate of fruits. The results showed that the compound preservative of carnauba wax and tea polyphenol had the best preservation effect.