EVALUATING TRADITIONAL AND COMMERCIAL KEFIR PRODUCTS FOR HUMANS AND COMPANION ANIMALS

Metras, Breanna Nichole

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https://hdl.handle.net/2142/124400 Copy

Description

Title

EVALUATING TRADITIONAL AND COMMERCIAL KEFIR PRODUCTS FOR HUMANS AND COMPANION ANIMALS

Author(s)

Metras, Breanna Nichole

Issue Date

2024-04-25

Director of Research (if dissertation) or Advisor (if thesis)

Swanson, Kelly S

Doctoral Committee Chair(s)

Miller, Michael J

Committee Member(s)

• Holscher, Hannah D
• Khan, Naiman A
• de Mejia, Elvira G

Department of Study

Nutritional Sciences

Discipline

Nutritional Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Kefir, fermented food, dairy, gut microbiome, canine, in vitro, fermentation, dietary fiber, probiotics

Abstract

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 have removed the use of kefir grains, which host novel microorganisms such as Lactobacillus kefiranofaciens and Kluyveromyces marxianus and contribute flavor compounds, carbonation, exopolysaccharides, and peptides. The resulting products sold in stores contain microbes starter cultures, but none are garnered from kefir grains. Given the lack of research in the field, the first aim was to evaluate five commercial kefir products for humans for label accuracy, microbial consistency, and viable live microorganisms. Our objectives were to measure viable microbial counts, characterize bacterial taxa of commercial kefir products, and compare enumeration and taxonomy data to label claims. To enumerate viable lactic acid bacteria (LAB), products were plated upon opening and following 14 d on deMan Rogosa and Sharpe (MRS) agar and incubated under anaerobic and aerobic conditions. High-throughput full-length 16S rRNA sequencing was used to assess microbial composition. Overall, each product was lacking in one or all categories. Our findings revealed that 66% of products with a guaranteed count of colony-forming units (CFU)/g overstated microorganism density by at least 1 log and that a moderate level of labeling accuracy is still needed for commercial kefir products intended for human consumption. The second aim was to evaluate six companion animal commercial kefir products, with the objectives of measuring viable microbial counts and characterizing bacterial taxa of commercial kefir products, and comparing them to label claims. High-throughput full-length 16S rRNA sequencing revealed significant microbial labeling inaccuracies and culturing techniques demonstrated there were fewer live microorganisms present at the time of opening than what the labels claimed. Microbial plating methods from Aim 1 were repeated for the companion animal products. Five products (83%) listed specific microorganisms, and four products (66%) guaranteed CFU/g on their label. Results from point of opening revealed that all commercial kefir products with a guaranteed CFU/g overstated the number of microorganisms present by at least 1 log, with only one product exceeding 1 × 109 CFU/g. Sequencing results demonstrated that none of the labels claiming specific bacterial genera and species on their labels were correct, and all products contained at least three additional bacterial species above the minimum detectable threshold (0.001% relative abundance) not disclosed by the manufacturer. The results from this aim demonstrated a low level of accuracy in the labeling of commercial kefir products intended for use in dogs and cats. The objective of the third aim was to test the effects of commercial or traditional kefir supplementation on apparent total tract macronutrient digestibility (ATTD) and fecal characteristics, microbiota populations, and metabolite and immunoglobulin (Ig) A concentrations of healthy adult dogs. Using a 3x3 replicated Latin square design, 12 healthy dogs were provided 60 mL/day of either non-fermented milk (control), commercial kefir, or traditional kefir for 28 d. Fresh fecal and blood samples were collected and analyzed at the end of each experimental period. Our results found that kefir supplementation had minor effects on the fecal microbiota populations, with a significantly higher relative abundance of Lactococcus in feces of dogs fed the traditional kefir (0.47%) than the controls (0.00%) or those fed the commercial kefir (0.00%). No significant differences were observed in ATTD, fecal characteristics, and fecal metabolite and IgA concentrations. The fourth aim was to use in vitro fermentation assays to determine the fermentation characteristics of dietary fibers using 1) fecal inoculum from dogs supplemented with starter- or grain-based kefirs; and 2) a starter bacterial culture or a grain kefir culture as inoculum. Canine feces or kefir inoculum were added to tubes containing a semi-defined medium and one of the fiber sources: pectin, cellulose, beet pulp, or chicory pulp. Over 18 h, increases in butyrate were greater (P<0.05) in tubes inoculated with feces from dogs fed grain kefir than those fed starter kefir or control tubes, and greater (P<0.05) in tubes inoculated with feces from dogs fed starter kefir than controls. In vitro fermentations inoculated with kefirs demonstrated that the microbiota present in both kefirs were able to ferment the fibers, but at a slower rate and incomplete metabolite profile. In conclusion, our data suggest that the current labeling of kefir products is often inaccurate and requires improvement as fermented beverages increase in consumption by both humans and companion animals. It is clear that the inclusion of kefir grains significantly impacts the microbial community of kefir beverages. Modifying the fermentation process by excluding kefir grains significantly impacts alpha diversity, minimally impacts the gut microbiota in vivo, and modifies the fermentation of dietary fibers and subsequent SCFA production in vitro. These studies have explored the different effects that grain and commercial kefir can have in dogs and how they impact microbial functionality in vitro. These data provide justification for further research into kefir products and other fermented foods and beverages.

Graduation Semester

2024-05

Type of Resource

Thesis

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