Psychrotrophic bacteria and milk and dairy products quality

The characteristics of microbial populations in raw milk at the time of processing has a significant influence on shelf life, organoleptic quality, spoilage and yields of the raw milk, processed milk as well as on the other dairy products. Unfortunately, cold and extended storage of raw milk, as a common practice in dairy sector today, favour the growth of psychrotrophic bacteria. Therefore, their count in the cooled milk is more than the ideal limit of 10% of the initial raw milk microbial population. Psychrotrophic bacteria are generally able to form extracellular or intracellular termoresistant enzymes (proteases, lipases and phospholipases) which can cause spoilage of milk and dairy product. In addition, besides exhibiting spoilage features, some species belonging to the psychrotrophs are considered as opportunistic pathogenic bacteria that carry inherent resistance to antibiotics and/or to produce toxins. In sense of quality, psychrotrophic bacteria have become major problem for today’s dairy industry as leading causes of spoilage and significant economic losses. This review focuses on the impact of psychrotrophs on quality problems associated with raw milk as well as on the final dairy products. In addition, the most common species and means of controlling strategies were also discussed