Effect of soymilk addition with different concentrations on some properties of cow milk yogurt

The present study was made with an attempt to produce yogurt by partial addition of different levels of soymilk to cow milk. Control was prepared with 100% cow milk and other samples prepared with cow milk and soymilk in the ratio of 95:5, 90:10, 85:15, 80:20, and 75:25 respectively. The control and different treatments of milk blends were analyzed for total solids and pH. The results found that the addition of soymilk leads to an increase of pH and total solids from 6.7, 11.94 % to 7.1 and 12.54 % for control and milk samples containing 25:75 levels of soymilk respectively. Yogurt samples were analyzed for some physicochemical analysis (pH, whey syneresis hardness) and organoleptic characteristics like (Appearance, flavor, body, texture acidity, and overall acceptability) during 14 days of storage at 4±1ºc. It was found that with increasing the levels of soymilk the syneresis decreased and the hardness was increased, the separated whey was (11.1 and 8.5 ml) and hardness of (6.5 and 19 gm cm-2) was obtained during 21 days of storage for control and sample containing 75:25 level. In general, the results of sensory properties as evaluated by the panelists indicates that the samples with increasing soymilk levels gained high scores of 13.8, 13.8 and 17.3 and low value of 21.0 and 11.2 in comparison to the results of the control sample which were recorded as 10.3, 7.8, 8.8, 28.0 and 13.0 for texture, body, appearance, flavor and acidity respectively during 14 days of storage.