Kefir is a self-carbonated refreshing fermented yoghurt that has been consumed for over 100 years for its various health benefits. It originated from communities in the Balkans in Eastern Europe and the Caucasian mountains. The beverage has a unique flavour due to its dense texture with an acidic and tart taste, low levels of alcohol, and other fermentation flavour products. It typically contains 89-90% moisture, 6.0% sugar, 3.0% protein, 1% of lactic acid, 1% of alcohol, 0.7% ash, 0.2% lipid, and 1.98 g/L of CO₂.

There are two types of kefir which are dairy and non-dairy kefir. Non-dairy kefir is a beverage made from the fermentation of kefir grains with a sugary solution. The main substrate used for the fermentation of non-dairy kefir is the organic brown or raw sugar solution. The dairy kefir is made from the fermentation of kefir grains using milk. Besides cow’s milk, kefir can be made with milk from other sources such as sheep, goat, buffalo, or soya. The figure below explains the methods to prepare dairy and non-dairy kefir beverages.

The feature that distinguishes kefir from other fermented dairy products is the use of kefir grains during fermentation and various microbial flora. The most commonly found bacterial genera in kefir are the Lactobacillus, Lactococcus, Streptococcus, and Leuconostoc. These genera often dominate (between 37% to 90%) of the total population present in both the kefir grain and milk with Streptococcus thermophilus, Lactococcus lactis subsp. lactis, Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus kefiri, Lactobacillus casei subsp. Pseudoplantarum, Lactobacillus brevis, and Lactobacillus kefir. These renowned probiotics coexist in a symbiotic association with other microorganisms found in kefir grains. This makes kefir an important probiotic beverage.

The microbiota of kefir grains may differ depending on the geographical origin of kefir grains strictly connected to climate conditions. The microflora composition in kefir may also vary depending on the substrate used during fermentation and culture maintenance methods (fermentation time, temperature, degree of agitation and ratio of kefir grains to substrate). It is recognized that this microbial diversity is accountable for the biological activities and physicochemical attributes of each kefir. However, some major Lactobacillus species are always existing because of their probiotic strain-specific properties.

This beverage consumption is associated with a wide array of health benefits, including anti-inflammatory, anti-oxidative, anti-cancer, anti-microbial, anti-diabetic, anti-hypertensive, and anti-hypercholesterolemic effects. As stated by the Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO), probiotics refer to live microorganisms that bestow a health benefit to the host when applied in sufficient amounts. Studies show that kefir’s exopolysaccharide has very significant physicochemical attributes and biological activities that add value to the products. All these health-promoting properties are linked to the kefir microorganisms, their interplays and their metabolic products during the fermentation process.

Moreover, kefir can be adapted into different substrates, allowing the production of new functional beverages to provide product diversification. Being safe and inexpensive, there is an immense global interest in kefir’s nutritional potential. Due to their promising benefits, kefir and kefir-like products have an excellent prospect for commercialization. Our paper reviews the therapeutic aspects of kefir to date, potential applications of kefir products in the health and food industries, and limitations. The review demonstrates a growing demand for kefir as a functional food due to a number of health-promoting properties.

Reference: Azizi NF, Kumar MR, Yeap SK, Abdullah JO, Khalid M, Omar AR, et al. Kefir and Its Biological Activities. Foods. 2021 Jun;10(6):1210.