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Antimicrobial effect and shelf-life extension by combined thermal and pulsed electric field treatment of milk

Walkling-Ribeiro, M., Noci, F., Cronin, D.A., Lyng, J.G., Morgan, D.J.
Journal of applied microbiology 2009 v.106 no.1 pp. 241-248
UHT milk, UHT treatment, anti-infective properties, food processing, heat, microorganisms, milk quality, pasteurization, pasteurized milk, pulsed electric fields, raw milk, refrigeration, shelf life, whole milk
The impact of a combined hurdle treatment of heat and pulsed electric fields (PEF) was studied on native microbiota used for the inoculation of low-fat ultra-high temperature (UHT) milk and whole raw milk. Microbiological shelf-life of the latter following hurdle treatment or thermal pasteurization was also investigated. UHT milk was preheated to 30°C, 40°C or 50°C over a 60-s period, pulsed for 50 μs or 60 μs at a field strength of 40 kV cm⁻¹ or for 33 μs at 50 kV cm⁻¹. Heat and PEF reduced the microbial count by a maximum of 6·4 log in UHT milk (50°C; 50 kV cm⁻¹, 33 μs) compared to 6·0 log (P greater-than-or-equal 0·05) obtained by thermal pasteurization (26 s, 72°C). When raw milk was treated with a combination of hurdles (50°C; 40 kV cm⁻¹, 60 μs) a 6·0 log inactivation of microbiota was achieved and microbiological milk shelf-life was extended to 21 days under refrigeration (4°C) vs 14 days in thermally pasteurized milk. Native microbiota was decreased by 6·7 log following conventional pasteurization. The findings suggest that heat and PEF achieved similar inactivation of native microbiota in milk and longer stabilization of microbiological shelf-life than thermal pasteurization. A hurdle approach of heat and PEF could represent a valid milk processing alternative to conventional pasteurization. Hurdle treatment might also preserve native milk quality better due to less thermal exposure.