ARS | Publication request: Cellular damage of Escherichia coli 0157:H7 and Salmonella spp. in apple juice treated with high hydrostatic pressure and thermal death time disks

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 17, 2012
Publication Date: August 19, 2012
Citation: Ukuku, D.O., Yamamoto, K., Kawamoto, S. 2012. Cellular damage of Escherichia coli 0157:H7 and Salmonella spp. in apple juice treated with high hydrostatic pressure and thermal death time disks. Meeting Abstract. American Chemical Society Meeting and Exposition.,Philadelphia, PA, August 19-23, 2012., Volume 1,Page 1.

Technical Abstract: Differences in membrane damage including leakage of intracellular UV-materials and loss of viability of Salmonella spp. and Escherichia coli O157:H7 bacteria in apple juice, pH 3.1 following thermal-death-time (TDT) disk and high hydrostatic pressure (HHP) treatments were investigated. Salmonella and E. coli O157H:H7 bacteria were inoculated in apple juice to a final 7.8 log CFU/ml and were thermally treated with TDT disks at 23 deg C, 45 deg C, 50 deg, 55 deg C, and 60 deg C for 4 min or HHP-treated at 350, 400, and 450 MPa at 25 deg C, 35 deg C, and 45 deg C for 20 minutes. Sub-lethal injury, leakage of UV- materials, and viability loss as a function of membrane damage of these bacterial pathogens were investigated by plating 0.1 ml of treated and untreated samples on non-selective Trypticase Soy Agar (TSA) and selective Xylose Lysine Sodium Tetradecylsufate (XLT4) for Salmonella and Sorbitol McConkey agar plates for E. coli bacteria with incubation at 36 deg C for 48 h. Sub-lethal injury occurred in Salmonella and E. coli populations thermally treated with TDT disk at 55 deg C and above and at HHP treatments of 35 deg C and above. Leakage of intracellular UV-materials and ATP of TDT disk injured cells were lower than the values determined from HHP-treated cells. Similarly, recovery of TDT injured cells occurred faster than HHP-treated cells during storage of treated samples at 25 deg C. The results of this study indicate that HHP treatment of 350 – 450 MPa at 30 deg C for 20 min and thermal treatments of 55 deg C and 60 deg C and immediate storage of treated samples at 5 deg C will inhibit recovery and complete inactivation of injured bacteria in apple juice to enhance the microbial safety of the treated juice.