91E-4 |
Effect of high hydrostatic pressure (HHP) treatment on survival of foodborne pathogens in freshly squeezed fruit juices |
H. ALPAS1, A. Bayindirli, and F. Bozoglu. (1) Food Engineering Department, Middle East Technical University, Ankara, 06531, Turkey For HHP studies the viability loss of foodborne pathogens as influenced by the magnitude of pressure, time and temperature, for different foodborne pathogens has been studied. Very little information is available on the viability loss of relatively-pressure resistant strains in fruit juices by HHP. The objective of this study is to combine HHP (345 MPa) with mild heat (40oC) for the inactivation of relatively pressure resistant strains of two Gram-negative (Escherichia coliO157:H7 933 and Salmonella enteritidis FDA) and Gram-positive (Listeria monocytogenes Ca, Staphylococcus aureus 485) foodborne pathogens inoculated in freshly squeezed orange (pH=3.76) and apple juice (pH=3.67) samples. The cells from early stationary phase were suspended in orange and apple juice samples at a final concentration of about 108 cells/ml. The cell suspensions in 2 ml-portions were pressurized to 345 MPa for 5 min at 40oC and were also heat treated at 40oC for control. With HHP more than 8-log cycle reduction was achieved in both fruit juices. However, viability loss due to thermal inactivation alone at 40oC after 5 min was less than 1.0 and 0.5 log cycles in Gram-negative and Gram-positive strains, respectively. Storage of HHP treated fruit juices for 24h at 4oC gave negative result on respective selective media. Also, incubation of food samples for an additional 1 week at 4oC showed no growth of all the strains studied. HHP pasteurization (345 MPa, 40oC) of high acid foods can be successfully applied to obtain high levels of destruction with respect to the inoculated foodborne pathogens. Also, the recommended shelf life of these products can be extended at refrigeration temperatures.
Session 91E, Nonthermal Processing: Nonthermal processing of foods
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