Inactivating microbes using high-pressure throttling

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8/04/2009-A report published in the August 2009 issue of Journal of Food Science explains how researchers at University of Georgia learned to inactivate Clostridium sporogenes PA 3679 ATCC 7955 in soymilk using continuous flow high-pressure throttling.

During this process, the temperature of soymilk increased due to instantaneous pressure release and additional heat was supplied by a heat exchanger to achieve a set temperature. The soymilk was immediately cooled to less than 40°C after a short preset hold time. The researchers reported a significant increase in the heat resistance in C. sporogenes spores when heated in soymilk compared to 0.1% peptone water. Continuous flow high-pressure throttling (CFHPT) from 207 or 276 MPa to atmospheric pressure reduced the microbial populations in inoculated soymilk up to 6 log cycles when the holding times were 10.4, 15.6, and 20.8 sec and the process temperatures were 85, 121, 133, and 145°C, respectively. The sporicidal effect increased as the operating pressure, time, and temperature were increased. More injured spores were found at 207 MPa than at 276 MPa, indicating that lower pressure caused cell injury whereas high pressure caused cell death.

“High hydrostatic pressure is an effective technique to satisfy consumer demand for fresh-like, minimally processed shelf-stable product,” said the researchers. “Many other alternative nonthermal food processing techniques are being studied and used but among all, the high-pressure processing has been the most promising. CFHPT system commercially pasteurizes the soymilk in seconds without any viable microorganisms. Time and temperature are key factors in inactivating microorganisms even under high pressure.”




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