Are current regulations for fermented kefir enough?
By Breanna Metras B.S., the University of Illinois Urbana Champaign, Division of Nutritional Sciences
Many traditional fermented foods, such as the dairy beverage kefir, are produced by small-scale artisans using milk and kefir grains. Increasing interest in fermented foods has demanded higher production, thus food and beverage companies have commercialized the fermentation process of kefir. To do this, companies remove the use of kefir grains, which host novel microorganisms such as Lactobacillus kefiranofaciens, Lactobacillus kefiri, and Kluyveromyces marxianus (1) and contribute flavor compounds, carbonation, exopolysaccharides, and peptides. Instead, companies inoculate vats of milk with preset starter cultures such as Lactococcus lactis, Lactococcus cremoris, Lactobacillus diacetylactis, Lactobacillus acidophilus, and Saccharomyces cerevisiae. In short, the resulting products sold in stores do contain microbes, but none are garnered from kefir grains (2). Our lab sequenced five commercial kefir products and six companion animal commercial kefir products sold in the USA and none of them contained the kefir-specific microbes mentioned above (2,3). Commercial producers of kefir cite limitations to the DNA extraction process and a responsibility to label microbial content only at the time of manufacture as the rational for missing several labeled bacterial species (4). Dr. Fatemeh Netaji has found similar microbial diversity in commercial kefirs sold in Germany as well as significantly more galactose and lactate, and significantly less glycerol than grain kefir (5). The yeast profiles of the commercial kefir also contained Kazachstanina unispora and Kazachstanina turicensis (5). In addition, this research found that the volatile organic compound profile of commercial kefirs clustered closely with the milk and yogurt tested rather than with grain kefirs (2). Due to large variations in microbes and chemical composition, the resulting flavor and mouthfeel of the two versions are also starkly different. Traditional kefirs have a slightly sour flavor, while commercially produced kefirs resemble the tartness of yogurt. Given these large differences between kefir produced from grains or from commercial starters, it begs the question: are they both still kefir?
Kefir is a great example of how the USA’s Food and Drug Administration (FDA) Standard of Identity regulations need to be expanded for fermented foods. Standards of Identity (SOI) are legal standards defined by the FDA, which contain the right to sell a product under a specific name by enforcing minimum quality standards, permitting included ingredients, and defining processing requirements. Regulations are largely reactionary, with the goal of human health and safety as their main motivation and microbial integrity failing to be a priority. Commercially-produced kefirs may be purchased by consumers expecting the anecdotal health benefits attributed to traditional kefirs, yet products being labeled as “kefir” are potentially misleading as there is no differentiation between the fermentation processes. Human clinical research in the last decade has also failed to differentiate traditional kefirs from commercial products, which leaves questions as to how traditional or commercial kefir may impact human health (6).
Label regulations in the USA are maintained by the FDA, which denotes approved live dietary microbes to be Generally Recognized as Safe (GRAS). State-specific legislation may further regulate product processing, storage conditions, and pH to prevent spoilage. Standard of identity regulations requiring minimal inclusion of specific microbes do exist for yogurt, but not for other fermented foods. Thus, differences due to manufacturing practices can potentially alter the local microbial ecosystems within the food matrix. As more fermented foods become produced on a large scale, maintaining the microbial integrity of these foods will be crucial for product consistency and efficacy. Each country has specific laws pertaining to live dietary microbes and associated health claims, yet none appear to have laws regulating the microbial integrity of fermented and functional foods. When time is spent forming definitions and standards for new products, legislation needs to follow swiftly for change to occur.
A potential path to keep kefir authentic may be to form a trade association to represent such interests on a political and international scale, like the Kombucha Brewers International group. This group works to maintain the compositional and microbial integrity of kombucha products sold around the world, while ensuring it doesn’t become taxed with beer and alcohol (7). This trade association was featured in a recent publication from the Codex Alimentarius International food standards (7), which also recommends kefir contain the microbes Lactobacillus kefiranofaciens, Lactobacillus kefiri, and Kluyveromyces marxianus for a product to be called kefir. Codex recommendations are a potential route for kefir and other fermented foods, but consensus on the presence of specific minimally included microbes will also be needed. Currently, the National Kefir Association demands that kefir is brewed under strict standards and contains specific cultures; yet they hold no regulatory authority and none of the novel kefir bacterial species above are listed on their website. From speaking with local producers of commercial kefir in Indiana USA, fermentation with kefir grains make the resulting kefir product less predictable in consistency, so they opt for preset commercial cultures to make their kefir. Another path towards keeping kefir’s microbes authentic is petitioning the FDA for a SOI regulation which specifies kefir-specific microbes as a minimal inclusion for a product to be called kefir: yogurt is a great example of a SOI currently in place. Consumers may be missing out on authentic kefir microbes and novel byproducts due to manufacturing tradeoffs for production consistency. More research will be needed to elucidate how the different microbial environments in kefir products confer potential benefits, if any, to consumers. With international markets increasing functional food sales each year, maintaining the integrity of fermented food cultures must be prioritized. Kefir produced from kefir grains or grain-derived microbes should be the only product sold under its name to keep its legacy authentic.
References
1. Rosa et al, Nutr. Res. Rev. 2017;30:82–96. DOI: 10.1017/s0954422416000275
2. Metras et al, JDS Communications. 2021;2:87–91. DOI: 10.3168/jdsc.2020-0056
3. Metras et al, J. Anim. Sci. 2020; 1:98-99. DOI: 10.1093/jas/skaa301
4. Nielson-Stowell. The Fermentation Association. 2021. www.fermentationassociation.org/kefir-brands-respond
5. Nejati et al, Appl. Sciences. 2022; 12:3838. DOI: 10.3390/app12083838
6. Bellikci-Koyu et al, Nutrients 2019;11:2089. DOI: 10.3390/nu11092089
7. Mukherjee et al, Front. Nutr. 2022;9:902642. DOI: 10.3389/fnut.2022.902642