Destruction of Salmonella enteritidis inoculated in liquid whole egg by high hydrostatic pressure: comparative study in selective and non-selective media E. Ponce, R. Pla*, E. Sendra, B. Guamis and M. Mor-Mur The destruction of Salmonella enteritidis inoculated in liquid whole egg at approximately 10 7 710 8 cfu ml 7l was studied under combinations of pressure (350 and 450 MPa), temperature (50, 20, 2 and 7158C) and time (5, 10, 15 min and cycles of 5  5 and 5  5  5 min). One non-selective medium (tryptone soy agar) and two selective media (brilliant green agar and salmonella-shigella) were used to evaluate viability of S. enteritidis after pressurization. The inactivation rate increased with pressure and exposure time, being minimal at 350 MPa and 7158C for 5 min (over 1 log 10 of reduction) and reaching total inactivation (8 log 10 of reduction) in several treatments at 508C. Treatments in cycles showed greater e¡ectiveness than continuous treatments of the same total time. The e¡ect of pressure was enhanced by elevated temperatures. The higher counts were obtained in the non-selective med- ium, indicating the presence of injured cells after pressure treatment. D-values obtained for two tem- peratures (2 and 208C) and di¡erent times (0^60 min) under controlled pressure (400 MPa) showed that microbial inactivation followed a ¢rst-order kinetics with a decimal reduction time evaluated in tryptone soy agar medium of 9 5 min at 28C and 8 8 min at 208C. # 1999 Academic Press Introduction Most infectious microbial pathogens present in foods are controlled by refrigeration, heat treatment, and/or the addition of selected anti- microbial agents. Egg pasteurization has been designed principally to control Salmonella, and the minimal e¤cient conditions reported by the USDA are 608C for 35 min (USDA 1969). Pasteurization causes no signi¢cant change in egg nutritional value, but the functional prop- erties (foaming, thickening, binding and emul- sifying), £avour and colour may be a¡ected. Heating leads to the formation or destruction of covalent bonds and other adverse changes, decreasing product quality (Forsythe 1970). Salmonella is a well-documented pathogen and long recognized in a wide range of foods, especially poultry products. Eggs and egg-con- taining foods have been implicated as sources of infection in a high percentage of human S. enteritidis outbreaks. Recently many countries ORIGINAL ARTICLE * Corresponding author. Received: 8 June 1998 Unitat deTecnologia dels Aliments/CeRTA, Facultat deVeterina© ria, Universitat Auto© noma de Barcelona, 08193 Bellaterra (Barcelona), Spain 0740-0020/99/040357 + 09 $30.00/0 # 1999 Academic Press Food Microbiology, 1999, 16, 357^365 Article No. fmic.1998.0248 Available online at http://www.idealibrary.com on