Honors Theses

Date of Award

Spring 5-14-2023

Document Type

Undergraduate Thesis



First Advisor

Erik Hom

Second Advisor

Georgianna Mann

Third Advisor

Colin Jackson

Relational Format



Kefir is a fermented beverage produced using sugar water or milk, kefir grains, either water kefir grains or milk kefir grains, respectively, and microbial aggregates consisting of diverse bacteria and yeasts. As kefir and fermented beverages in general are increasing in popularity, research related to optimal sensory characteristics and consumer-approval is vital. Desirable sensory characteristics for kefir beverages include low sour taste/aroma, high sweetness, carbonation, and high viscosity (Surja et al., 2019; Margareth et al., 2020). Production methods of kefir can alter sensory characteristics, but sensory characteristics are likely strongly influenced by the microbial composition of the grains/product. Thus, an understanding of specific microbial species present within kefir grains is vital. Using traditional microbiological culturing methods, two bacterial species and 3 yeast species were isolated from one heirloom of water kefir grain and one heirloom of milk kefir grain – one bacterial species and one yeast species were isolated from the water kefir grain, and one bacterial species and two yeast species were isolated from the milk kefir grain. Knowledge of the microbial composition of kefir grains could be used to trace the origins of volatile scent compounds produced during the kefir fermentation process that impart unique sensory characteristics of kefir products. The cumulative findings of this thesis lay the groundwork for developing kefir grains with defined microbiota in order to produce kefir with specific desirable sensory characteristics.

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