Impact of Yeast Types on Quality Characteristics and Storage Stability of Industrial Kefir

Kefir is a fermented dairy product that contains many types of lactic acid bacteria and different types of yeast. Yeasts in kefir culture are important in creating the unique properties of kefir. When yeasts are not included in kefir production, the unique properties of kefir do not emerge. In this study, the effects of various yeast microorganisms that can cause negative effects, such as swelling and deformation, in industrial kefir production on product quality characteristics were investigated. For this purpose, a commercial yeast-free kefir culture was supplemented with selected yeasts: <i>Kluyveromyces marxianus</i> (KM), <i>Debaryomyces hansenii</i> (DH), <i>Kluyveromyces lactis</i> (KL), <i>Saccharomyces boulardii</i> (SB), <i>Saccharomyces cerevisiae</i> (SC), <i>Candida colliculosa</i> (CC), <i>Yarrowia lipolytica</i> (YL), and <i>Geotrichum candidum</i> (GC) used in kefir production. Some physicochemical, rheological, microbiological, and sensory properties of the kefirs were examined during 28 days of storage. As a result of the research, the highest hardness and viscosity values (131.00 ± 1.41 g-1236.50 ± 47.38 cp) were observed in kefirs containing <i>G. candidum</i>, while the highest CO₂ amount (151.40 ± 1.07 mg/100 mL) was determined in kefirs containing <i>S. cerevisiae</i> (<i>p</i> < 0.05). While serum separation was not determined in any sample, the highest water holding capacity (58.00% ± 00%) was determined in kefirs containing <i>Y. lipolytica</i>. In terms of sensory evaluation, kefir enriched with <i>C. colliculosa</i> received the highest overall acceptance. In general, the use of different yeast types in kefir production is of great importance, especially in terms of gas-carbon dioxide (CO₂) formation and product quality.