Milk was subjected to a combination process involving reduced heat treatment (RHT) of 117°C for 2 s and nisin (75 and 150 IU ml-1). The microbial activity and other quality aspects were compared
with a RHT control (without nisin) and with a ultrahigh temperature (UHT) milk processed at 142°C for 2 s. Nisin was found to inhibit microbial growth for products stored without refrigeration, and
RHT-nisin samples stored at 30°C showed very low spoilage rates during 150 days, although not low enough to satisfy requirements for commercial sterility. RHT-nisin samples could be distinguished from
and were preferred to the UHT control. Significant browning occurred during storage at 30°C and above but was less in the RHT-nisin milk samples compared with the UHT milk. In RHT-nisin milk samples
stored at 20 and 10°C, no microbial activity could be detected in most samples after storage for 1 year. The effectiveness of this combination of RHT, nisin, and low storage temperatures against gram-positive
spore-forming bacteria suggests potential for use of nisin in extended shelf life products.
Document Type: Research Article
School of Food Biosciences, The University of Reading, Reading RG6 6AP, England 2:
Danisco Cultor, Beaminster DT83DZ, Dorset, England
Publication date: February 1, 2001
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