Inactivation of bacterial spores in milk using pulsed electric fields

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Ross, Alexander
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University of Guelph

This thesis is an investigation of the inactivation of bacterial spores in milk using pulsed electric field (PEF) technology. Spores inoculated into raw skim milk were treated with low-energy instant-charge reversal pulses at high electric field strengths. No inactivation of ' Bacillus stearothermophilus' 145 or 'Bacillus licheniformis ' 519 spores occurred in raw skim milk due to PEF application at moderate or mildly elevated temperatures. Addition of nisin to milk prevented outgrowth of 'B. licheniformis ' 519 spores, but no extra inactivation occurred when nisin was combined with PEF application. No inactivation of 'B. stearothermophilus' 145 or ' B. licheniformis' 519 spores, or germinated or outgrowing spores of ' B. licheniformis' 519, occurred in dilute saline solutions treated by PEF. PEF treatments using low-energy instant-charge reversal pulses are not capable of destroying bacterial spores in raw skim milk or dilute saline solution. The potential for a spore-inactivation process relying on PEF technology is very limited.

milk, bacterial spores, pulsed electric fields, raw skim milk, nisin