In the EU regulations, general microbiological requirements for raw milk are laid down; however, the qualitative composition of microflora is not defined. In the absence of hygiene during milking, milk becomes contaminated with microflora that, despite the cold storage, can multiply and, at the same time, produces extracellular enzymes (mainly proteases and lipases), which contribute to the quality deterioration of milk and dairy products. Owing to their heat resistance, the enzymes of bacterial origin are a serious problem for the dairy industry. In the paper, there are characterized the contamination sources of raw milk with psychrotrophic microflora and the qualitative composition of psychrotrophic microorganisms as are the properties of their enzymes and the effects of the activity of proteases and lipases while storing milk and its products.