ISSN:
1745-4549
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Raw skim milk was treated with high-intensity pulsed electric fields (PEF) at 40 kV/cm, and 30 pulses of 2 μs duration each, or by combining thermal processing at 73 or 80C for 6 s followed by a PEF process at 50 or 30 kV/cm, 30 pulses at 4 or 3 Hz. The microbiological quality of the skim milk was monitored for 14, 22 and 30 days during storage at 4C. The combination of thermal/PEF-processed skim milk exhibited greater microbial quality than PEF or thermally processed skim milk. The bacterial counts of skim milk decreased with increasing electric field intensity and number of pulses. On day 14, the PEF-processed skim milk reached 7.2, 6.5 and 6.3 log cfu/mL after PEF processes at 10, 20 or 30 pulses compared with 7.6 log cfu/mL in unprocessed skim milk. The combination of thermal/PEF-processed skim milk achieved bacteria counts of 4.1 and 4.9 log cfu/mL at the end of the 22 and 30 days of refrigerated storage, respectively. The acidity of skim milk was more affected by heat, and the combination of heat and PEF processes than by PEF alone. During refrigerated storage of skim milk, the bacterial growth was dependent on the electric field intensity, process duration and storage time. A synergistic effect between temperature and pulsed electric fields was observed at 73 and 80C when the skim milk was processed with 50 or 30 kV/cm.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1745-4549.2005.00029.x
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