Kefir is a fermented milk beverage made from the symbiotic relationship between bacteria and yeast found in kefir grains. The Caucasian people have been making kefir by hand since the late 19th century. This tradition has spread to other parts of the world and is now incorporated into many populations' regular diets due to its nutritional and therapeutic properties. Kefir is known as the 21st-century yoghurt because of its large number of microorganisms and their microbial interactions, potential bioactive compounds from microbial metabolism, and health benefits. Kefir cure depression is considered a natural probiotic.
Kefir Grains
Kefir grains are recovered by straining milk after the fermentation process, where they serve as a natural starter culture during the kefir-making process. These grains are made up of immobilized microorganisms on a polysaccharide and protein matrix that supports the symbiotic coexistence of several yeast and bacterial species. There is a fairly stable population of microorganisms in this ecosystem, and they interact with and have an impact on other community members. In order to inhibit microorganisms like food pathogens and contaminants and promote grain growth, this population synthesizes bioactive metabolites.
Microbiological Aspects
Lactic acid bacteria (LAB) are mainly in charge of converting lactose in milk into lactic acid in kefir, which lowers the pH and preserves the milk. Additional microbial components of kefir comprise lactose-fermenting yeasts, which yield CO2 and ethanol. Acetic acid bacteria (AAB) and non-lactose fermenting yeast are also involved in the process. Following fermentation, the grains experience a 5-7% increase in biomass. The proportions of microorganisms in the grains during their growth in milk are different from those in the finished product. This variation is related to several aspects of the fermentation process. Effects of kefir on the final microbial composition and nutritional profile are noteworthy, showcasing how the interplay of LAB, yeast, and AAB contributes to the unique characteristics of the end product.
Kefir microbiota has traditionally been studied using conventional microbiological techniques. Despite their value, these techniques occasionally lack the discrimination necessary to distinguish between closely related species or novel ones. You can know more about them on kefirwala. The growth and survival of individual strains depend on one another due to the microbial symbiotic association found in the grains. When microorganisms are separated from grains, they frequently grow poorly in milk and/or exhibit decreased biochemical activity.
Distribution of Microorganisms in Kefir Grains
In the context of understanding the microorganism distribution within kefir grains, there has been ongoing research, and the findings remain debatable. According to a group of researchers, rod-shaped bacteria and uncommon lactococci are primarily found on the surface area of grains, while yeasts are typically located in the inner and intermediate grain zone. These dynamics are crucial to grasp for individuals interested in the health benefits associated with drinking kefir.
On the other hand, another group of researchers argues that yeasts are distributed in both the inner and outer grain areas, with the morphology of the rod-shaped bacteria being the primary distinction between the two. Contrary to earlier findings, they found no sign of yeast in the inner grain region and observed a predominance of rod-shaped bacteria. It's worth noting that, from a perspective relevant to those who consume kefir, some writers have observed that there are fewer cells in the inner than in the outer portion of the grain.
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