Quality evaluation of non-fat goat milk yogurt supplemented with purple sweet potato flour

In the present work, the supplementation of purple sweet potato flour as a prebiotic at concentrations of 1, 2, and 3% enhanced the probiotic efficacy. These three concentrations of purple sweet potato flour reduced the fermentation time from 4.5 – 5.5 h as compared to the control © recipe (7–5 - 8.0 h). Panellists scored highest overall acceptability for non-fat goat milk yogurt with 1% purple sweet potato flour (S1 recipe). The S1 recipe was selected to evaluate the quality change during storage for 27 days at 4°C. The L* and b* values decreased, whereas the a* value increased. Non-fat goat milk yogurt had low hardness. The supplementation of purple sweet potato flour did not significantly affect yogurt hardness, and reduced the percentage of whey separation during the storage period. Purple sweet potato flour also promoted the survival of Streptococcus thermophilus but reduced viable cells of Lactobacillus delbrueckii subsp. bulgaricus. The S1 recipe was demonstrated as a healthy food with a shelf-life of 27 days, and could appeal to the health-conscious consumers.