Quality properties of yogurt added with hot water concentrates from Allium hookeri root

Hot water extraction concentrate was prepared from Alliun hookeri root (AHR) to evaluate its applicability to yogurt. The highest antioxidant activity of hot water concentrates was obtained under extraction conditions of 4 hr at 95°C. Antioxidant activities measured by DPPH radical assay, ABTS radical cation assay, reducing power, and cheating activity were highly correlated with total phenolic (89.51 mg/g) and total flavonoid (52.71 mg/g) contents, with R values of 0.94 and 0.96, respectively. Yogurt was fermented with a commercial lactic acid bacteria mixed strain (Yo-mix™ 305) for 10 hr at 42°C after addition of 0~10% (w/w) hot water concentrates from AHR to yogurt base. As fermentation proceeded, pH and °Brix of yogurt decreased from 6.57 ~ 6.60 to 4.34 ~ 4.51 and from 8.10 ~ 8.90% to 4.60 ~ 5.25%, respectively, whereas titrate acidity, viscosity, and viable cell numbers increased from 0.22 ~ 0.23% to 1.01 ~ 1.10%, from 0 mPa･s to 202.55 ~ 290.50 mPa･s, and from 6.40 ~ 6.80 log CFU/mL to 8.60 ~ 9.20 log CFU/mL, respectively. There was no significant difference in any sensory attribute between the control and 2.5% addition group, suggesting that 2.5% hot water concentrate from AHR could be used to manufacture yogurt.