Biodiversity of refrigerated raw milk microbiotika and their enzymatic spoilage potential

Publication Type

Journal contribution (peer reviewed)

Authors

von Neubeck, M.; Baur, C.; Krewinkel, M.; Stoeckel, M.; Kranz, B.; Stressler, T.; Fischer, L.; Hinrichs, J.; Scherer, S. Wenning, M.

Year of publication

2015

Published in

International Journal of Food Microbiology

DOI

10.1016/j.ijfoodmicro.2015.07.001

The refrigerated storage of rawmilk selects for psychrotolerant microorganisms, many of which produce peptidases and lipases. Some of these enzymes are heat resistant and are not sufficiently inactivated by pasteurisation or even ultra-high temperature (UHT) treatment. In the current study, 20 different raw cow's milk samples from single farms and dairy bulk tanks were analysed close to delivery to the dairies or close to processing in the dairy for their cultivable microbiota as well as the lipolytic and proteolytic potential of the isolated microorganisms.
Altogether, 2906 isolates have been identified and assigned to 169 species and 61 genera. Pseudomonas, Lactococcus and Acinetobacter were the most abundant genera making up 62% of all isolates, whereas 46 genera had an abundance of b1% and represent only 6.6%. Of all isolates, 18% belong to hitherto unknown species, indicating that a large fraction of themilk microbiota is still unexplored. The potential of the isolates to produce lipases or peptidases followed inmany cases a genus or group specific pattern. All isolates identified as members of the genus Pseudomonas exhibitedmainly lipolytic and proteolytic activity or solely proteolytic activity. On the other hand, nearly all isolates of the genus Acinetobacter were lipolytic but not proteolytic. Only 37% of all tested lactic acid bacteria (LAB) showed enzymatic activity at 6 °C and the type of activity was proteolytic in 97% of these cases.