Effects of level of solids on physical and sensory properties of elephant foot yam-added milk concentrate

Abstract

Elephant foot yam (EFY), a nutritious tuber consumed as vegetable in India and other tropical countries is well recognized in Ayurveda for its healthful attributes. Being a good source of starch and, therefore, a potential thickening agent, pre-cooked powdered EFY was incorporated into milk and examined for its thickening potential as a function of yam solids (EFYS) and milk solids (TMS). Apparent viscosity and other physical properties viz., sedimentation, heat coagulation time (HCT-130°C), whiteness index (WI) along with sensory attributes of the resulting EFY-milk dispersion were studied using response surface methodology. Increasing solids level (9.17-14.82% TMS and 0.19-2.31% EFYS) resulted in linearly increasing (p<0.01) apparent viscosity (5.9-12.9 mPa.s), yam solids having more pronounced effect than milk solids, although the interaction between the two factors was non-significant. The increase in solids level was accompanied by decrease (p<0.01) in HCT (50.5-3.1 min) and WI (84.03-78.41), the effect of EFYS being accentuated at higher levels of TMS. Correspondingly, the sensory consistency score (42.7-19.4 on 100-point linear scale) declined with both increasing TMS and EFYS, whereas the color (96.0-72.7), mouthfeel (96.3-80.0) and flavor scores (90.6-66.6) all decreased, but essentially with increasing yam solids and not perceivably with milk solids. It was found that for given (tolerable) heat stability and sensory attributes of yam-milk mix, the levels of two components could be optimized to achieve desired thickening in various milk-food applications.