A Big World in Small Grain: A Review of Natural Milk Kefir Starters

Abstract

Milk kefir is a traditional fermented milk product whose consumption is becoming increasingly popular. The natural starter for kefir production is kefir grain, which consists of various bacterial and yeast species. At the industrial scale, however, kefir grains are rarely used due to their slow growth, complex application, bad reproducibility and high costs. Instead, mixtures of defined lactic acid bacteria and sometimes yeasts are applied, which alter sensory and functional properties compared to natural grain-based milk kefir. In order to be able to mimic natural starter cultures for authentic kefir production, it is a prerequisite to gain deep knowledge about the nature of kefir grains, its microbial composition, morphologic structure, composition of strains on grains and the impact of environmental parameters on kefir grain characteristics. In addition, it is very important to deeply investigate the numerous multi-dimensional interactions among different species, which play important roles on the formation and the functionality of grains.

Antimicrobial Activity of Six International Artisanal Kefirs against Bacillus cereus, Listeria monocytogenes, Salmonella enterica Serovar Enteritidis, and Staphylococcus aureus

“…and LAB ( Lactobacillus sp., Lactococcus sp., Leuconostoc sp., etc.) have been isolated and identified from kefir grains [ 14 , 15 ]. Kefir grains have been shown to have regional differences in microbial composition, producing variability in the kefirs produced, due in part to local LAB finding a niche in the grains [ 16 ].…”

The Effect of Fermentation with Kefir Grains on the Physicochemical and Antioxidant Properties of Beverages from Blue Lupin (Lupinus angustifolius L.) Seeds

“…Nowadays, a great number of novel functional foods are available on the market with dairy foods and beverages representing an important segment [ 1 ]. One of the most popular dairy foods with undisputed benefits from consumption is kefir, that can be prepared from different milk types, such as goat, buffalo, sheep, camel, or cow via microbial fermentation (inoculating milk with kefir grains, consisting of lactic acid bacteria and yeasts) [ 6 , 7 ]. In the last decades, many scientific reports highlighted nutritional properties of kefir and health benefits owing to its antimicrobial, anticancer, gastrointestinal tract effects, gut microbiota modulation, cholesterol-lowering activity, and anti-diabetic effects [ 3 , 6 , 7 , 8 , 9 ].…”

“…One of the most popular dairy foods with undisputed benefits from consumption is kefir, that can be prepared from different milk types, such as goat, buffalo, sheep, camel, or cow via microbial fermentation (inoculating milk with kefir grains, consisting of lactic acid bacteria and yeasts) [ 6 , 7 ]. In the last decades, many scientific reports highlighted nutritional properties of kefir and health benefits owing to its antimicrobial, anticancer, gastrointestinal tract effects, gut microbiota modulation, cholesterol-lowering activity, and anti-diabetic effects [ 3 , 6 , 7 , 8 , 9 ]. Recently, milk consumption has been declining, and consumer demand for cow’s milk alternatives increased as a result of the increase in the diagnosis of lactose intolerance, allergies, and cholesterol issues [ 10 , 11 , 12 , 13 ].…”

Quantification of Major Bacteria and Yeast Species in Kefir Consortia by Multiplex TaqMan qPCR

“…Results concerning the presence and abundance of specific species in kefir differ a lot among various studies, which is due to either differences in kefir samples or the role of different methods for the identification of microbiota (Nejati et al, 2020). As a result, a meaningful comparison of results among different studies are not easily feasible.…”

“…More than 50 microbial species were identified in different milk kefirs (Bourrie et al, 2016;Liu et al, 2019). It is supposed that several inter-microbial actions are responsible for the maintenance of the kefir grains' integrity as well as their bio-functionalities as robust starter cultures (Nejati et al, 2020). The microbial composition of kefir grains can change due to several factors, such as the cultivation conditions (e.g., temperature, grain to milk ratio, milk source) and the geographical origin of kefir (Prado et al, 2015).…”