Sterilization Of Freeze Concentrated Green Tea By Pulsed Electric Field

In this paper, the sterilization effectiveness of pulse electric field (PEF) on liquid extract from green tea(LEGT) which was freeze concentrated was investigated. In which the relationship between the sterilization results and parameters include electric field strength, treatment time, pulse width combined with frequency were studied. The tests were carried out in different concentrations at low and ambient temperatures respectively, the quality attributes such as pH values electric conductivity, amino acid, Vc et al before and after the PEF treatments and that of the treated ones after storage. The content of the study could be summarized as follow:(1) The LEGT which was extracted with the facilitation of PEF and then freeze concentrated. The Extraction rate was indicated by polyphenols. The factors such as ratio of tea to water, electric field strength, treatment time which affect the extraction yields was also investigated. The results showed that the optimized conditions of the ratio of tea to water, electric field strength and treatment time were 1:30,33.33kV/cm 82 u s respectively. At the optimized conditions the extraction yields of polyphenols was 13.43%. The LEGT reached 1.85°Brix in concentration.(2) The LEGT was been sterilized with PEF. The results showed that effects of sterilization was different from different microorganisms, the magnitude of the killed from the highest one to the lowest one were yeast, Staphylococcus aureus, Salmonella, E. Coli and Penicillium. The results showed that the PEF had a good effect on the pathogens. The higher the electric field strength, the better the effect of the sterilization was. The longer the treatment time the the better the effect of it.(3) The sterilization of PEF were carried out at different temperatures and at different concentrations. The results showed that at lower temperature the sterilization effect was a little bit better than that at higher temperature, sterilization of PEF at low temperature was of feasibility in practice.(4) Catechin composition in pulse processing concentrated green tea was analysised by HPLC. the physical and chemical analysis of the samples before and after the pulse sterilization indicators before and after. Come to the high-voltage pulse sterilization can better maintain product quality. The pulse processing samples in the colony total value of the storage period and the main physical and chemical indicators fluctuation.