Psychrotrophic microbiota in milk and fermented milk products

Abstract

Milk and dairy products form a significant part of the human diet. Temperature control is considered as the key to extend shelf life for dairy products. Psychrotrophs grow at temperature such as 7oC or lower but had higher optimal growth temperature. Most psychrotrophs produce extracellular enzymes while growing in milk and deteriorate its quality. Six types of samples constituting buffalo milk, flavored milk, curd, shrikhand, lassi and butter were collected in different seasons to study the psychrotrophic microbiota. Sixty psychrotrophic bacteria were grouped into fifteen clusters of very similar isolates. One isolate from each of the fifteen clusters of closely related isolates was identified by phylogenetic analysis namely Stenotrophomonas maltophilia, Pseudomonas putida, Pseudomonas stutzeri, Enterobacter hormaechei, Macrococcus caseolyticus, Exiguobacterium acetylicum, Exiguobacterium indicum, Micrococcus luteus, Kocuria rosea, Staphylococcus equorum, Ornithinmicrobium humiphilum, Planococcus psychrotoleratus, Bacillus cereus and two isolates upto genus level namely Exiguobacterium spp. and Kocuria spp. Fatty acid profile of milk sample inoculated with lipolytic psychrotrophic bacterial isolate was determined using Hydrolytic Extraction Gas Chromatographic method.