Is Kefir Beneficial in my pet's raw diet? How to make Kefir & Kefir Cheese (video)

May 28, 2021

We've probably all heard about how beneficial it can be to include kefir, or fermented milks and fermented cheeses, in our pet's raw bowls (or cooked food bowls, or kibble filled bowls, you get the gist...), so we've run out to the nearest pet store to pick up a carton or two (or 3 or 4) of prepackaged kefir and kefir cheese. 

But what is kefir?
Kefir is essentially a fermented milk drink that tends to be thinner than yogurt, often described as "drinkable yogurt" when referring to its consistency/thickness. 

Plain kefir is not only suitable to give to our pets (who can tolerate it), but it is also most often consumed by humans, as the fermented milk is supposed to be loaded with probiotics that can help aid in digestion and giving your immune system an overall boost

Personally, I never really consumed much kefir, but once bringing Nolo home, I found myself spending a sizeable amount of money on Answers Fermented Raw Cow Milk Kefir or Open Farm Kefir because it made for some really yummy diy doggy treats. And it was an added bonus that I was able to offer a different source of probiotics, other than the probiotic powder I was giving him, which I rotated throughout his weekly feeding schedule.

Then it happened...I discovered that kefir and kefir cheese can be made AT HOME (& I was about to save a lot of money!). So I went ahead and purchased some kefir grains online and I got to fermenting my own full fat cow's milk and raw goats milk at home! But naturally, I wanted to know just how beneficial kefir can be, especially since it is something I supplement in my dogs' diets on a regular basis. So I went ahead and looked into the probiotic qualities of kefir and kefir cheese. 

What I found on the topic has been shared below...

Yeasts from kefir grains: isolation, identification, and probiotic characterization - Gabriela Diosma (2013)

“Kefir—a traditional beverage whose consumption has been associated with health benefits—is a logical natural product to investigate for new probiotic strains. The aim of the present work was to isolate and identify kefir yeasts and select those with acid and bile tolerance to study their adhesion to epithelial cells and their transit through mouse gut. From 4 milky and 3 sugary kefir grains, 34 yeast strains were isolated and identified by means of classical microbiological and molecular-genetic methods (whole-cell protein pattern, internal-transcribed-spacer amplification, and analysis of restriction-fragment–length polymorphisms). We identified 4 species belonging to 3 genera—Saccharomyces cerevisiae (15 strains), Saccharomyces unisporus (6 strains), Issatchenkia occidentalis (4 strains), and Kluyveromyces marxianus (9 strains)—and selected 13 strains on the basis of resistance to low pH and bile salts. Among the strains selected, Kluyveromyces marxianus CIDCA 8154 and Saccharomyces cerevisiae CIDCA 8112 were further studied. Both strains evidenced the capacity to adhere to epithelial intestine-derived cells in vitro and to survive passage through the gastrointestinal tract of BALB/c mice. The investigation of the potential probiotic features of these kefir-yeast strains should be useful for the development of novel functional foods.” 

“In the present study 15 strains of S. cerevisiae, 6 strains of S. unisporus, 4 strains of I. occidentalis, and 9 strains of K. marxianus were isolated from the complex microbial consortium of kefir grains. Among them, 13 isolates have high acid- and bile-resistance phenotypes and are thus potentially suitable for probiotic purposes. K. marxianus CIDCA 8154 and S. cerevisiae CIDCA 8112 also exhibited a capacity to adhere to intestinal epithelial cells in vitro, survive passage through the gastrointestinal tract of Balb/c mice, and during that intestinal residence spread all along the tract with higher abundance throughout the distal portions. At the end of the administration both yeast strains become cleared from the gut within 5 days. Although further studies about the health benefits from and mechanisms involved in these findings are still required, the results obtained here should nevertheless be useful for the development of new probiotic products based on the different strains of yeast isolated from kefir.”

This experimental study from 2013 investigates the probiotic qualities of kefir yeast strains
The experiment was carried out in vivo with mice, and aimed to measure the indirect probiotic qualities of the kefir yeast, such as the ability of the yeast strains to make it through the digestive tract of the mice, adhere to the intestinal tract, and to disperse at a high volume during passage. 

These are indirect probiotic qualities because while they are desirable characteristics for a probiotic microorganism, they do not determine whether the microorganism is able to provide resistance to pathogenic, or harmful, bacteria. Among the many strains of beneficial/probiotic yeast derived from kefir grains, the study isolated K. marxianus CIDCA 8154 and S. cerevisiae CIDCA 8112 as the two best performing yeast strains in terms of peripheral probiotic characteristics. 

Antibacterial activity of different formulations of cheese and whey produced with kefir grains- Simone Weschenfelder (2018)

“The development of different products that confer health benefits on the population is a challenge for those who work with food. The aim of this study was to elaborate two formulations of kefir cheese (C1 and C2) and whey (W1, W2), and to evaluate their in situ antibacterial activity against microorganisms of interest in food. Pasteurized milk, powdered milk and kefir grains were used in preparing the products and their percentage composition was determined. C1, C2, W1 and W2 were contaminated with five different logarithmic fractions (A = 8log to E = 4log CFU/ml) of Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 11229), with antibacterial activity assessed over 0, 24, 48 and 72 hours of exposure. The results demonstrated the antibacterial activity of kefir cheese and whey, especially after 24 hours. Escherichia coli was the most sensitive of the bacteria, with maximum antibacterial activity seen in the cheese at population densities D and E, and in the whey at densities B, C, D and E after 48 and 72 h, showing that the in situ antibacterial activity of foods produced with kefir grains tends to be lower when compared with studies in vitro. The greater the nutrient content of the food, the lower the antibacterial activity seen, probably due to the protective action that the nutrients confer on the microorganisms against bacteriocins and the metabolites from fermentation.”

“When tested in situ the kefir derivatives demonstrated antibacterial activity, the greatest activity being against Escherichia coli (ATCC 11229). However, the antibacterial activity only reached maximum after 48 and 72 hours confrontation of C1, C2, W1 and W2 with smaller population densities of the microorganism, reinforcing the importance of hygiene when preparing these foods, and highlighting the capacity of Escherichia coli and Staphylococcus aureus to survive in the product. The results from determining the percentage composition serve as the basis for the development of kefir derivatives and their inclusion in diets, and show that the greater the nutrient content of the food, the lower the antibacterial activity seen in situ.”

In contrast to the previous experiment, this study aimed to measure the direct probiotic/antibacterial properties of kefir derivatives. One thing to note is that this experiment did not isolate the microorganisms with the kefir derivatives, only the pathogenic bacteria strains that were exposed to the kefir products. 

While the kefir cheese and whey products tested in the study did exhibit antibacterial activity, the researchers note that this activity was most significant after 2-3 days of contact. While antibacterial/probiotic effects of kefir are found, it is important to understand that peak probiotic effect is not immediate and a contaminated sample of kefir product could be harbouring harmful bacteria strains if not prepared correctly

Microbiological, technological and therapeutic properties of kefir: a natural probiotic beverage- Analy Machado de Oliveira Leite (2013)

“Kefir is a fermented milk beverage produced by the action of bacteria and yeasts that exist in symbiotic association in kefir grains. The artisanal production of the kefir is based on the tradition of the peoples of Caucasus, which has spread to other parts of the world, from the late 19th century, and nowadays integrates its nutritional and therapeutic indications to the everyday food choices of several populations. The large number of microorganisms present in kefir and their microbial interactions, the possible bioactive compounds resulting of microbial metabolism, and the benefits associated with the use this beverage confers kefir the status of a natural probiotic, designated as the 21th century yoghurt. Several studies have shown that kefir and its constituents have antimicrobial, antitumor, anticarcinogenic and immunomodulatory activity and also improve lactose digestion, among others. This review includes data on the technological aspects, the main beneficial effects on human health of kefir and its microbiological composition. Generally, kefir grains contain a relatively stable and specific microbiota enclosed in a matrix of polysaccharides and proteins. Microbial interactions in kefir are complex due to the composition of kefir grains, which seems to differ among different studies, although some predominant Lactobacillus species are always present. Besides, the specific populations of individual grains seem to contribute to the particular sensory characteristics present in fermented beverages. This review also includes new electron microscopy data on the distribution of microorganisms within different Brazilian kefir grains, which showed a relative change in its distribution according to grain origin.”

“Kefir is a traditional example of the co-existence of bacteria and yeasts and the importance of this symbiotic relationship seems clear, since it is necessary to produce compounds beneficial to health. Although the evidence is not conclusive and further studies should be conducted, the existing scientific studies demonstrate the health benefits reported empirically by historical kefir consumption. Currently, the application of probiotics in the food industry is in expansion and understanding the symbiotic relationships between different microorganisms present in food, as well as their interactions, could assist in the improvement of technological processes.

The quality of traditional kefir is mainly influenced by the microorganisms present in kefir grains and kefir processing conditions. Although scientists and food companies attempted to develop a commercial "kefir-type" beverage produced by different cultures and mesophilic and thermophilic LAB, or even pure cultures isolated from kefir grains, their success when compared to traditional kefir is limited. We suggest that this limitation is due to the microbial diversity present in kefir grains and their interactions, which can determine the probiotic and therapeutic properties of the final product, as well as peculiarities conferred by certain minority groups present in different grains. However, from an industrial point of view, these developments are welcome, given the lack of standardization in the production and marketing of traditional kefir.”

This literature review on the topic serves as a good conclusion following our discussion of the two previous experimental studies. The review also discusses the processes of kefir production which brings into question the ability to extrapolate probiotic effects from one method of production to another

The conclusion acknowledges that traditional kefir preparation (milk inoculation with variable amounts of grains and fermentation for a period between 18-24hrs at 20-25 ºC. At the end of the fermentation process the grains are sieved and can be used for a new fermentation or kept 1-7 days in fresh milk, while the kefir beverage is stored at 4 ºC, ready for consumption) is found to have more significant probiotic effects over commercially produced kefir using series of fermentation. 

When produced in a traditional manner under sterile conditions, kefir is shown to be a safe and effective probiotic to improve gastrointestinal health. 


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Please consult physicians/veterinarians, and/or other trustworthy science-based sources for advice on human and animal dietary questions.

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