Enhanced inactivation of bacterial lipases and proteinases in whole milk by a modified ultra high temperature treatment.
Cultures of Pseudomonas spp. strains P10, P12 and P15 grown in whole milk which contained approximately 1 x 10(8) viable bacteria ml-1 demonstrated near linear increases in the concentration of short-chain free fatty acids and trichloroacetic acid soluble free amino groups at 20 degrees C, following either ultra high temperature (UHT) treatment (140 degrees C for 5 s) or dual heat treatments (140 degrees C followed by either 57, 60 or 65 degrees C). The dual heat treatments reduced the rates of lipolysis and proteolysis compared to the UHT treatment by up to 25-fold. The dual heat treatment utilizing 60 degrees C for 5 min also effectively limited both lipase and proteinase activities in raw milk culture samples which had contained either 6 x 10(6), 5 x 10(7) or 1 x 10(8) viable bacteria ml-1. In this system enzyme activities were reduced by up to 10-fold following dual heat treatment compared to UHT treatment alone.
Bucky
A R
AR
Department of Microbiology, University of Leeds, UK.
Hayes
P R
PR
Robinson
D S
DS
D000818:Animals; D002417:Cattle; D010450:Endopeptidases / Q000032:analysis*; D005260:Female; D006358:Hot Temperature; D008049:Lipase / Q000032:analysis*; D008892:Milk / Q000201:enzymology* / Q000382:microbiology; D011549:Pseudomonas / Q000201:enzymology*
D008049:Lipase; D010450:Endopeptidases