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Agricultural biotechnology and food biotechnology
In recent years, there has been considerable interest in non-thermal milk processing. The objective of the present study was to assess the efficacy of two non-thermal technologies (manothermosonication; MTS, and pulsed electric fields; PEF) in comparison to thermal pasteurisation, by assessing the microbial levels of each of these milk samples post-processing. Homogenised milk was subjected to MTS (frequency; 20 kHz, amplitude; 27.9 μm, pressure; 225 kPa) at two temperatures (37 °C or 55 °C), before being immediately treated with PEF (electric field strength; 32 kV/cm, pulse width; 10 μs, frequency; 320 Hz). Thermal pasteurisation (72 °C, 20 s) was included as a control treatment. Microbial content of each milk sample was monitored over a 21-day period. It was determined that milks treated with MTS/PEF at 37 °C and 55 °C contained lower microbial levels than raw milk for a certain duration, but after 14 days milk which had been pasteurised by conventional methods contained significantly (P < 0.05) less microorganisms. However, milks treated with MTS/PEF contained significantly (P < 0.05) fewer microorganisms than raw milk at each time point. Although not as effective as pasteurisation, the present study demonstrates the ability of MTS/PEF treatment to reduce microbial content of milk, while avoiding prolonged heat exposure to temperatures such as those used during conventional (thermal) pasteurisation.
Halpin, R. et al. (2013) Combined Treatment with Mild Heat, Manothermosonication and Pulsed Electric Fields Reduces Microbial Growth in Milk. Food Control, Volume 34, Issue 2, December 2013, Pages 364-371 DOI :10.1016/j.foodcont.2013.05.008