Optimization of Red Dragon Fruit, Red Beet and Black Rice Extract Concentrations in Goat Milk Synbiotic Kefir: Effects on Organoleptic Quality, pH and Viscosity

Goat milk kefir is a probiotic-rich functional food with potential health benefits, yet its strong goaty aroma reduces consumer acceptance. Incorporating natural extracts rich in bioactive compounds, such as red dragon fruit (Hylocereus polyrhizus), red beet (Beta vulgaris L.) and black rice [Oryza sativa (L.) indica], may improve sensory quality and enhance functional properties.

Synbiotic kefir was prepared from goat milk with the addition of dragon fruit, beet and black rice extracts at concentrations of 0.5%, 1.0%, 1.5% and 2.0%. Sensory evaluation (hedonic and hedonic quality tests) was performed by 55 semi-trained panelists. pH and viscosity were analyzed instrumentally. Data were analyzed using Friedman and Kruskal-Wallis non-parametric tests.

Extract type and concentration significantly affected color, texture, taste and overall acceptability (p<0.05), but not aroma (p>0.05). The best treatment was beet extract at 1.5% (E2K3), which scored highest in overall acceptability (3.51). Dragon fruit extract at 2% produced the most preferred aroma (3.53). pH values ranged from 3.80-3.93, remaining stable across treatments. Viscosity ranged from 210.88-363.63 cP, with beet extract producing the highest viscosity, while higher extract concentrations tended to reduce viscosity. Addition of beet extract at 1.5% provided the optimal balance of sensory attributes, pH stability and viscosity in goat milk synbiotic kefir. These findings highlight the potential of combining goat milk with plant-based extracts to enhance the acceptability and functionality of fermented dairy products.