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The destruction and sublethal effect of cycle or continuous high pressure treatment on Escherichia coli in different frozen and unfrozen media

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1800723.(doi:10.13031/aim.201800723)
Authors:   Chunfang Wang, Hosahalli S. Ramaswamy, Wei Sun, Hao Wang, Songming Zhu, Yong Yu
Keywords:   High pressure, Escherichia coli, inactivation, frozen Chinese bayberry juice, frozen carrot juice.

Abstract. The effect of high pressure (300-400 MPa; one or two cycles and 5 min) on inactivation of Escherichia coli ATCC 25922 in frozen suspension, Chinese bayberry juice and carrot juice were evaluated. Experiments were carried out in a specially designed container to reach a subzero temperature for sample but process at room temperature. Nonselective medium (brain heart infusion agar, BHIA) and selective medium (violet red bile agar, VRBA) were used to enumerate the survial and injured E. coli cells. After treating at 300 MPa with 5 min, the reduction of E. coli in frozen suspension was 3.62 logCFU/mL (BHIA count) and it was undetectable on VRBA medium. As for acid frozen Chinese bayberry juice, survived E. coli was undetectable after treating with 200 MPa, 5 min (BHIA medium). The reduction of E. coli in frozen carrot juice treated after 300 MPa at one cycle was 2.10 logCFU/mL, and increased to 4.01 logCFU/mL after two cycles (BHIA count). Injured E. coli cells were observed both in unfrozen and frozen samples of E. coli suspension and Chinese bayberry juice. The frozen sample state contributed to a much better inactivation on E. coli after high pressure.

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