The effect of nisin on the keeping quality of reduced heat-treated milks.
Milk was subjected to a combination process involving reduced heat treatment (RHT) of 117 degrees 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 degrees C for 2 s. Nisin was found to inhibit microbial growth for products stored without refrigeration, and RHT-nisin samples stored at 30 degrees 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 degrees 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 degrees 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.
School of Food Biosciences, The University of Reading, England.
T I
TI
Wirjantoro
M J
MJ
Lewis
A S
AS
Grandison
G C
GC
Williams
J
J
Delves-Broughton
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003116:Color; D005511:Food Handling / Q000379:methods*; D005519:Food Preservation / Q000379:methods; D006358:Hot Temperature; D015416:Maillard Reaction; D008892:Milk / Q000382:microbiology*; D009561:Nisin / Q000494:pharmacology*; D013649:Taste; D013997:Time Factors
D000900:Anti-Bacterial Agents; D009561:Nisin