Paper Authors and Title

Amie McDonald (South East Technological University), Nabla Kennedy, “Analysis of the Microbial Composition of Homemade and Commercial Kefir Milk”


Kefir is a beverage that contains a complex composition of microbial species which have been seen to provide health promoting attributes. In the current study the microbial composition of commercially bought milk kefir from the brand Biotiful in Ireland was compared to kefir made in an Irish household. This study focused on the milk product kefir, a dairy beverage consisting of a wide diversity of species including, but not limited to, lactic acid bacteria, acetic acid bacteria, yeast and Bifidobacterium. The aim of this current study was to characterise these species and analyse the microbial diversity within homemade and commercial kefir milk using culture-dependent and culture-independent methods.

Culturing showed the abundance of lactic acid bacteria, Bifidobacterium spp., acetic acid bacteria, and yeasts. Lactic acid bacteria were the most abundant microbes in both homemade and commercial kefir milk, followed by Bifidobacterium. Sanger sequencing determined that Geotrichum was a commonly-found yeast species in homemade kefir. Data from NGS determined that the most common bacterial genera in the homemade sample were Leuconostoc whereas Lactobacillus was the most abundant in the commercial sample. Firmicutes were identified as the most abundant phylum in both the homemade and commercial milk kefir. The overall findings of the study acknowledged that homemade kefir had a greater microbial diversity compared to the commercial kefir milk. A limitation to the study was the limited amount of time in the laboratory.


Download and view Amie McDonald’s slides.