Hurdle is alternative to HTST processing for liquid foods.

Liquid foods and beverages have been implicated in various foodborne outbreaks and recalls. Pulsed electric fields (PEFs) are a non-thermal processing technique for liquid foods and could be considered an alternative preservation method to high-temperature short-time (HTST) pasteurization. PEFs have a similar bacterial inactivation effect as HTST pasteurization, and leave the product with better quality because they generate less heat.

Irish scientists investigated how a hurdle approach with moderate heat in combination with PEFs would impact the native microflora found in low-fat ultra-high-temperature (UHT) milk and whole raw milk. It appears that this type of hurdle might be an alternative preservation technique for this and other liquid foods.

In experiments, UHT milk was pre-heated at moderate temperatures of 30 C, 40 C or 50 C. This was followed by pulse treatments for 50 ms and 60 ms at an electric field strength of 40 kV per cm, or for 33 ms at 50 kV per cm. The researchers found that moderate heat and PEFs reduced the bacteria by a maximum of 6.4 logs in UHT milk (50 C; 50 kV per cm for 33 ms) compared to 6.0 logs obtained by HTST pasteurization for 26 seconds at 72 C.

When raw milk was exposed to a combination of hurdles-50 C; 40 kV per cm for 60 ms--a 6.0-log inactivation of bacteria was achieved, and the milk's shelf life was extended to 21 days under refrigerated conditions at 4 C, compared with 14 days for HTST-processed milk. Native bacteria were reduced by 6.7 logs following HTST treatment.

Based on these results, a hurdle approach using moderate heat and PEFs could be an alternative for milk preservation. This hurdle achieved similar bacterial reductions and a longer shelf life compared to conventional HTST pasteurization.

Further information. Francesco Noci, College of Life Sciences, School of Agriculture, Food Science and Veterinary Medicine, Agriculture and Food Science Center, University College Dublin, Belfield, Dublin 4, Ireland; phone: +353 1 716 7603; email: francesco.noci@ucd.ie.

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