PSIX-11 From vat to bowl: Ethanol vs. Brewer’s yeast in dog food palatability.

Abstract Brewer’s yeast (BY) and ethanol yeast (EY) are promising ingredients in canine nutrition due to their potential to enhance flavor. Although they share similar nutritional profiles, BY and EY are cultivated under different pH conditions, which may affect protein content, digestibility, and flavor characteristics. Additionally, the use of processing techniques, such as spray drying, autolysis (A), enzymatic hydrolysis (H), and centrifugation to obtain yeast extract (YE), modifies the yeast cell structure, potentially influencing nutrient availability, digestibility, and palatability. This study evaluated how yeast origin and processing affect dry dog food preferences when used as a coating. Seven palatability trials were conducted with 20 adult dogs, using dry diets coated with 0.5% yeast processed as inactive dried (ID), A, H, or YE. The comparisons included IDEY vs. IDBY, AEY vs. IDEY, HEY vs. AEY, YEEY vs. IDBY, HEY vs. YEBY, YEEY vs. YEBY, and AEY vs. YEBY. Food acceptance was assessed through preference and consumption tests, measuring initial choice and total intake over 4 days. Each dog received 400 g of each yeast-coated diet daily, alternating bowl positions daily to prevent side bias. Data were analyzed using paired t-tests at a 5% significance level. No significant difference was observed between IDEY vs. IDBY (P >0.05; Figure 1). This finding reinforces the similar nutritional profiles of BY and EY. Additionally, no significant difference was observed between AEY vs. IDEY (P >0.05; Figure 2), which suggests that the spray-drying process does not promote a high release of flavor-active compounds, such as peptides or free amino acids, resulting in similar palatability. In contrast, YEEY was preferred over IDBY (P< 0.05; Figure 3), with an intake ratio of 4.16 and average initial preferences of 59%. The YEEY was also significantly preferred over YEBY (P< 0.05; Figure 4), with an intake ratio of 5.72 and initial preference of 64%. Both HEY and AEY were favored over ELC (P< 0.05; Figures 5 and 6, respectively), with intake ratios of 4.14 and 5.39 and average initial preferences of 62% and 74%, respectively. However, in the AEY vs. HEY test, HEY was significantly preferred (P< 0.05; Figure 7), with an intake ratio of 2.11 and initial preference of 35%. Hydrolysis, using exogenous enzymes, enhances nucleotide, peptide, and free amino acid content, resulting in a more intense sensory profile, as seen in the strong preference for HEY. Similarly, during yeast extract production—via autolysis and separation of the soluble fraction—flavor-active compounds are concentrated, enhancing the sensory profile and contributing to higher palatability. Despite BY having slightly higher fat content and protein digestibility, EY was consistently preferred. In conclusion, yeast processing significantly influences palatability, with HEY and YEEY being the most effective coating ingredients.