EVALUATION OF PROBE ULTRASOUND ON THE TECHNOLOGICAL PROPERTIES AND STABILITY OF GOAT MILK KEFIR GEL

Kefir is a fermented beverage known for its health benefits, attributed to its rich nutritional composition and the presence of probiotic microorganisms. However, kefir made from goat milk (CL) presents important technological challenges, such as low water retention capacity (WRC) and high syneresis, factors that compromise its physicochemical stability and sensory acceptance. Such limitations require the adoption of technological interventions that contribute to improving product quality. In this context, the present study aimed to evaluate the effects of probe ultrasound (US) on the technological properties and stability of kefir gel produced with CL. The CL was subjected to pretreatment with US (20 kHz, 420 W), at an intensity of 60% and a time of 5.5 min. The samples (control and sonicated) were subsequently subjected to heat treatment (80 °C/30 min, cooled to room temperature, inoculated with kefir starter culture and incubated at 25 °C until reaching pH 4.6. The analyses were conducted focusing on the centesimal composition, physicochemical properties, color parameters, WHC and syneresis, evaluated throughout the refrigerated storage (1, 7 and 14 days at 5 °C). The composition of the control sample presented protein contents of 3.86 ± 0.07, fat of 2.90 ± 0.10, moisture of 89.77 ± 0.95, ash of 0.96 ± 0.15 and carbohydrate of 2.51 ± 1.10, while the sonicated sample presented 3.46 ± 0.20, 2.91 ± 0.11, 90.05 ± 0.12, 0.80 ± 0.05 and 2.78 ± 0.22, respectively. Regarding the physicochemical properties, greater pH stability was observed in the sample treated with US throughout storage (p < 0.05) when compared to the control. Regarding color, sonication resulted in a significant increase in luminosity (L*), from 92.21 ± 0.31 (control, day 1) to 94.10 ± 0.23 (sonicated, day 1), maintaining this trend during storage. A reduction in the b* value was also recorded, indicating a less yellowish hue in the treated samples, possibly due to better homogenization of the matrix constituents. The sonicated samples presented significantly higher %WHC and lower syneresis rates, specifically, an increase in WHC of 50.1% and a decrease in syneresis in 46.2% on the first day of storage. During the 14-day storage period, the results of the sonicated sample remained superior to the control sample, highlighting a better stability of the gelled matrix. These results indicate that the use of ultrasound favors the formation of a more stable gel, with better water retention and less syneresis, optimizing the technological quality of kefir.