Inactivation of Escherichia coli K12 in phosphate buffer saline and orange juice by high hydrostatic pressure processing combined with freezing

Bulut, S. and Karatzas, K. A.G. (2021) Inactivation of Escherichia coli K12 in phosphate buffer saline and orange juice by high hydrostatic pressure processing combined with freezing. LWT-Food Science and Technology, 136 (1). 110313. ISSN 0023-6438 doi: 10.1016/j.lwt.2020.110313

Abstract/Summary

Synergistic action of high hydrostatic pressure (HHP) and freezing on inactivation of Escherichia coli K12 in phosphate buffered saline (PBS) was investigated by employing response surface methodology. Samples containing E. coli K12 were stored at 4, −24 and −80 °C overnight before they were pressurized. A maximum of 1.83 log reduction of CFU·ml-1 was obtained following a 9-min treatment at 400 MPa and 4±1 °C in samples stored at 4 °C whereas, 5.63 and 6.83 log reductions were obtained in samples frozen at −24 and −80 °C, respectively. Major disruption of E. coli cells observed by scanning electron microscopy and increased amounts of DNA and RNA measured in pressure treated frozen PBS samples indicated that the main mechanism of inactivation in frozen samples was due to cell rapture. The validity of enhanced microbial inactivation by freezing before HHP for a real food system was tested by using orange juice. Pressurization (250 MPa, 15 min) of frozen (−80 °C) orange juice resulted in 4.88, 4.15 and 4.61 log CFU·ml-1 reductions in number of E. coli for the samples having pH 3.2, 4.5 and 5.8, respectively. In the absence of freezing, the same treatment caused only up to 0.42 log reduction in samples having pH 4.5 and 5.8.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/94832
Item Type	Article
Refereed	Yes
Divisions	Life Sciences > School of Chemistry, Food and Pharmacy > Department of Food and Nutritional Sciences > Food Microbial Sciences Research Group
Publisher	Elsevier
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