Enhancement effect of composite loquat and wolfberry juice on the quality characteristics and antioxidant activity of yogurt

Process optimization, quality characteristics evaluation and in vitro antioxidant activity analysis of a novel yogurt enriched with composite loquat-wolfberry juice was systematically carried out in this study. After optimization through single-factor and response surface experiments, an experimentally observed sensory score (81.74) of the compound yogurt was achieved under the conditions of 8% composite raw material juice, 6.27% white sugar and 5.99 h fermentation time, which was close to the predicted maximum value of 79.60 given by the regression equation. Subsequently, the obtained compound yogurt showed significantly better sensory quality, higher titratable acidity, lower pH value, and greater water holding capacity than the plain yogurt. Moreover, the compound yogurt achieved improved apparent viscosity, textural and thixotropic properties. Additionally, the microstructural analysis revealed a denser network structure in the compound yogurt when compared to the plain yogurt. Furthermore, the compound yogurt had stronger in vitro 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl free radical scavenging ability than the plain yogurt at each tested mass concentration. These results demonstrated that the composite loquat-wolfberry juice was an effective food ingredient for improving the quality characteristics and in vitro antioxidant activity of yogurt.