In Australia, raw milk is required to undergo
thermal processing so that the milk is safe to consume. Recent interest in the consumption of raw
milk and raw milk products has led to the consideration of alternative dairy
processing technologies that will not compromise milk quality and safety. One technology being investigated is pulsed
electric field (PEF) processing, which can be used alone or in combination with
thermal processing. In the current
study, PEF was investigated at two processing conditions and compared with two
thermal treatments and a raw milk control.
PEF was conducted at ~30 kV/cm for a total of ~22 µs. Outlet temperatures were either 63°C (P1) or 53°C
(P2) for a total time of ~15 s before quickly cooling the milk to below 20°C. Thermal controls were heated to either 72°C
(T1, pasteurisation) or 63°C (T2, thermisation) for 15 s. Milk bottles (1L) from each treatment were
incubated for two weeks at 4 and 8°C, for a total of 20 bottles. The milk was assessed for Total Plate Count,
pH and lipid oxidation. The entire
experiment was replicated twice. Raw
milk was the quickest to reach spoilage (>106 cfu/mL) in 1-2 d at
both temperatures. At 4°C, T1 could last
10-14+ d, P1 could last 10-11 d, and T2 and P2 could last 6-7 d before spoilage
levels were reached. Storage at 8°C
reduced the time until spoilage by approximately one half for the respective
treatments. A drop in pH occurred after
a change in counts was observed. Short
chain acids dominated the volatile profile of the milk samples. T1 and P1 followed similar trends and appeared
most stable from volatile analysis, reflecting better quality indicated by lower
total plate counts. The PEF treatment (P1)
has potential to be comparable to thermal pasteurisation (72°C for 15s).