Milk, due to its high nutritional content, can support a rich microbiota. These microorganisms enter milk from a variety of sources and, once in milk, can play a number of roles, both promoting health and causing spoilage and disease and not least, facilitating dairy fermentations .
The specific composition of the milk microbiota directly impacts on the subsequent development of dairy products . Microorganisms can bring about the fermentation of milk through the production of lactate and have a variety of different impacts on the sensory, texture, flavour and organoleptic properties of resultant products
It is generally accepted that the lactic acid bacteria (LAB), a group of bacteria that ferment lactose to lactate, are a dominant population in bovine, goat, sheep and buffalo milk, prior to pasteurisation. The most common LAB genera in milk include Lactococcus, Lactobacillus, Leuconostoc, Streptococcus and Enterococcus. Other strains of non-LAB genera are also encountered in milk, as well as various yeasts and moulds . Human milk on the other hand is typically dominated by Streptococcus, Staphylococcus, Lactobacillus and Bifidobacterium spp. .
Quigley et al. have comprehensively reviewed the various microbial populations found in raw milk and the methods employed for their detection. They also focus on their sources, their subsequent significance with respect to industrial applications and the contribution of specific populations to food quality and health. They note that, in the food industry the negative impact of removing LAB and other bacteria on subsequent food fermentations has been addressed for some time through their re-introduction in the form of starter and adjunct cultures. Similarly, once established definitively, it may be possible to restore the benefits associated with the consumption of raw milk and specific microorganisms therein, through the re-introduction of these microorganisms after processing. Thus, the microbial composition of raw milk is likely to continue to be the focus of much attention in the future. / by Gillian van Beest
Quigley et al. (2013), The complex microbiota of raw milk. FEMS Microbiology Reviews, 37: 664–698.