Effects of kombucha use on shelf life and quality characteristics in meat and meat products

This study investigated the effects of adding kombucha in different proportions to the meat formulation (%5 and %10), edible coating material (%5 and %10), and both meat formulation and coating material in equal amounts (%2,5 and %5) on the oxidative and microbial stability, as well as the quality criteria of cooked ground beef during its shelf life. The experimental groups were stored under atmospheric conditions at +4°C for 14 days. The kombucha used in the study was produced under laboratory conditions using green tea. Total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, and ferric reducing antioxidant power (FRAP) analyses were conducted before and after fermentation. In the meat model system, cooking loss, moisture, ash, fat, and protein analyses were performed on the production day, while pH, water activity, color, texture profile analysis, microbiological analyses, thiobarbituric acid reactive substances (TBARS), and lipid hydroperoxide analyses were carried out throughout production and storage. The results showed that, after fermentation, there was an increase in TPC and FRAP values, whereas DPPH values decreased (p<0.05). The addition of 10% kombucha to the meat formulation, as well as the addition of 5% kombucha to both the meat formulation and coating material, increased cooking loss values (p<0.05). While 10% kombucha addition to the meat formulation reduced moisture content, the highest moisture values were obtained in all coated groups (p<0.05). The highest ash content was observed in groups where the coating material contained kombucha (p<0.05). The highest fat content was determined in the control group (K), which contained no kombucha and had no coating applied (p<0.05). The addition of kombucha to the meat formulation resulted in higher fat content compared to the coated groups (p<0.05). The highest protein content was observed in the group where 10% kombucha was added to the formulation (p<0.05). The addition of 5% and 10% kombucha to the meat formulation significantly reduced meat pH (p<0.05). Furthermore, lower a* values were detected in groups where 5% and 10% kombucha was added to the meat formulation, as well as in groups where 2.5% and 5% kombucha was added to both the meat formulation and coating material, compared to kombucha-free uncoated and/or coated groups (p<0.05). Microbiological analysis results showed no significant differences among the experimental groups in terms of total mesophilic aerobic bacteria, coliform group bacteria, and yeast-mold counts. According to TBARS and lipid hydroperoxide analysis results, the highest oxidation levels were found in the control (K) group, which contained no kombucha and had no coating applied, while the lowest oxidation level was observed in group B, which contained 10% kombucha in the formulation (p<0.05). The oxidation levels in the kombucha-free coated group (L) were lower than those in the kombucha-free uncoated control group (K) (p<0.05). Additionally, the inclusion of kombucha in the coating material further reduced oxidation levels compared to the kombucha-free coated group (L) (p<0.05). Overall, TBARS and lipid hydroperoxide results indicated that incorporating different levels of kombucha into the meat formulation was the most effective method for limiting lipid oxidation (p<0.05). Even in the absence of kombucha, using the coating material alone significantly reduced TBARS and lipid hydroperoxide formation (p<0.05). Furthermore, this effect was enhanced when kombucha was added to the coating material. The findings of this thesis suggest that kombucha has the potential to improve the oxidative stability of cooked ground beef. While the direct incorporation of kombucha into the meat formulation better limited oxidative changes, it also increased cooking loss and pH reduction. Therefore, adding kombucha to an edible coating material offers potential for enhancing oxidative stability without negatively affecting physicochemical properties.