Development of Fermented Skimmed Milk Fortified with Yellow Sweet Potato (ipomoea Batatas L.) with Prebiotic and Antioxidant Activity

The research was conducted to develop functional fermented milk by using yellow sweet potato (Ipomoea batatas L.) as a prebiotic and antioxidant agent. Fermented milk treatments were manufactured from skimmed milk using a probiotic culture (Lactobacillus acidophilus La5) and were fortified with sweet potato powder at levels of 15 g.l(-1), 35 g.l(-1) and 55 g.l(-1). At day 1 and after 14 days of cold storage, fermented milk treatments were evaluated for viability of probiotic bacteria, viscosity, water-holding capacity (WHC), total phenolic compounds (TPC), total carotenoids (TC), antioxidant activity (AA) and sensory as well as texture profile attributes. Fortification with sweet potato powder stimulated the growth of probiotic bacteria. The bacterial counts in control fermented milk and fortified by 55 g.l(-1) sweet potato powder were 7.74 log CFU.g(-1) and 10.28 log CFU.g(-1), respectively. The addition of sweet potato powder enhanced viscosity and WHC in all treatments. High TPC, TC and AA were observed in fermented milk with added sweet potato powder, and the effect of the fortification was found to depend on its concentration. The results indicated that fortification with sweet potato powder improved the textural profile, particularly at concentrations of 35 g.l(-1)and 55 g.l(-1). After 14 days of storage, viscosity, AA, firmness and adhesiveness increased. Sensorically, all fermented milk treatments were acceptable.