The usability of microencapsulated red beetroot betalains as a colorant in kefir

Kefir is a fermented dairy product that has positive effects on human health due to its content of probiotic microorganisms. With its ability to support digestive system health, strengthen the immune system, and provide high nutritional value, it has become a prominent functional beverage with increasing consumption in recent years. In line with rising consumer demand, the production of fruit-flavored and differently colored kefir products has become widespread to diversify traditional kefir offerings. In this thesis study, the natural colorant betalain was stabilized through encapsulation and added to kefir, aiming to produce a visually attractive, pink-colored product. In addition, the study aimed to improve color stability. The encapsulation process enhances the resistance of betalain pigments against environmental factors such as heat and light, thereby contributing to the maintenance of color stability throughout the product's shelf life. Kefir samples produced in the study were stored at 4°C and subjected to various analyses at specific intervals. In this context, pH value, titratable acidity, color parameters (L*, a*, b*), mineral content, total phenolic content, betalain concentration, and microbiological characteristics of the samples were analyzed. Based on the obtained data, the effects of using natural colorants on the functional and sensory quality of kefir were evaluated. According to microbiological analysis results, the total mesophilic aerobic bacteria and lactic acid bacteria counts in the kefir samples decreased significantly until the 7th day of storage, with changes observed thereafter found to be statistically insignificant. Yeast and mold counts showed a fluctuating trend during storage. On day 0, the counts of mesophilic aerobic bacteria and lactic acid bacteria were 18.94±1.22 log CFU/ml and 18.46±0.52 log CFU/ml, respectively, which decreased to 8.17±0.26 log CFU/ml and 9.19±0.91 log CFU/ml by day 21. The type of sample did not significantly affect microbial content. The addition of red beet to kefir through specific methods led to a decrease in L* and b* values, while increasing a*, C*, and h values compared to plain kefir. The highest redness (a*) value was observed in the sample colored with red beet concentrate encapsulated with gum arabic. All colored samples showed higher total phenolic content compared to the control group. The degradation kinetics of betalain pigment were also investigated. The stability of the pigment varied depending on the encapsulating material used. For the KS sample, the degradation rate constant (k) was found to be 0.0041 day⁻¹, with a half-life (t₁/₂) of 169.02 days and R² value of 0.8782. The MD sample showed a lower k value of 0.0024 day⁻¹, with a calculated t₁/₂ of 288.75 days (R²: 0.8013). For the GA sample, k was 0.0028 day⁻¹, t₁/₂ was 247.50 days, and R² was 0.8483. The betalain pigment was the most stable in the sample prepared with maltodextrin. Both maltodextrin and gum arabic were found to be effective wall materials for encapsulation. Sensory analysis of kefir samples revealed that the plain kefir was the most preferred by consumers. However, all samples received sensory scores above 7.4, indicating that coloring kefir with natural pigments did not adversely affect overall sensory acceptance. In fact, some samples and parameters (such as color, aroma, and overall liking) showed positive effects. These findings suggest that kefir products colored with betalain pigments can be a visually and sensorially appealing alternative for consumers In conclusion, this thesis highlights the potential use of natural additives in functional dairy products and scientifically supports improvements in color stability, antioxidant capacity, and overall product quality through the encapsulation of betalain pigment. Furthermore, it aims to contribute to the literature on the effects of natural food colorants on product quality. Keywords: betalain, colour, encapsulation, kefir, red beetroot, storage period