Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2013
Publication Date: 12/8/2013
Publication URL: http://handle.nal.usda.gov/10113/59458
Citation: Hsu, H., Sheen, S., Sites, J.E., Huang, L., Wu, J. 2013. Effect of high pressure treatment on the survival of Shiga-Toxin producing Escherichia coli in strawberries. Food Microbiology. 40:25-30. Interpretive Summary: High pressure processing (HPP), a non-thermal means to kill microbes, has been demonstrated effective in reducing the Shiga Toxin-producing Escherichia coli strains (STECs) in strawberries. At moderate operation conditions (e.g. 350MPa, 10 degree C, 5 min), six log microbial counts reduction (1000000 per gram food) is achievable in high acid fruits (e.g. strawberry, pH less than 4.6), which may provide a useful processing alternative for food producers to produce temperature sensitive products and enhance microbial (food-borne pathogens) food safety.
Technical Abstract: Most fresh produce, such as strawberries, receives minimal processing and is often eaten raw. Contamination of produce with pathogenic bacteria may occur during growth, harvest, processing, transportation, and storage and presents a serious public health risk. Strawberries have been implicated in an outbreak of Escherichia coli O157:H7 infection that sickened 15 people, including one death. Strawberries may also be contaminated by other serogroups of non-O157 Shiga toxin-producing E. coli (STEC), including O26, O45, O103, O111, O121 and O145, which have become known as the ”Big Six” or “Top Six” non-O157 STECs. The objective of this research was to explore the potential application of high pressure processing (HPP) treatment to reduce or eliminate STECs in fresh strawberry puree (FSP). FSP, inoculated with a six-strain cocktail of the “Big Six” non-O157 STEC strains or a five-strain cocktail of E. coli O157:H7 in vacuum-sealed packages, were pressure-treated at 150, 250, 350, 450, 550, and 650 MPa (1 MPa = 1000000 N per squared m) for 5, 15, and 30 min. HPP treatment, at 350 MPa for long than 5 min, significantly reduced STECs in FSP by 6-log CFU per gram from the initial cell population of ca. 8-log CFU per gram. Cell rupture was observed by scanning electron microscopy (SEM). The results demonstrated that the HPP treatments can be potentially used to control both non-O157 and O157:H7 STECs in heat sensitive products.