Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Dairy

This work of thesis was implemented to study the effect of whey protein concentrate (WPC), whey protein isolate (WPI) and glycomacropeptide (GMP) as a partial substitution of milk solids not fat (MSNF) in ice cream formula by 1, 2, 3 and 4% of (MSNF). Mixes and resultant ice cream samples were analyzed for their chemical, physicochemical and rheological properties as well as the sensory quality attributes. There was no remarkable effect of adding whey proteins as partial substitution of MSNF on total solids or fat percentages, while total protein, ash, and lactose content were significantly affected. Specific gravity was significantly affected with the ratio of substitution in both mixes and resultant ice cream and therefore the weight per gallon and overrun percent was significantly changed in the samples. Apparent viscosity as well as flow time of mixes was significantly increased. Flow behavior was also affected showing higher yield stress. Increasing WPC, WPI and GMP in ice cream mixes resulted in a building up of structure leading to increase in the sample viscosity. The shear stress increased significantly with increasing the substitution ratios. Also, flow behavior index (n) decreased by increasing the substitution levels of whey proteins. The consistency coefficient (k) was more affected by the presence of whey proteins in the recipe than the flow behavior index. Herschel-Bulkley behavior (building up of structure and increasing of sample viscosity) was observed in ice cream mix by increasing the substitution levels of whey proteins. Back-extrusion results represent a decreasing of hardness values of resultant ice cream. While, during storage, there was a little increase of hardness values. Energy input values decreased by increasing substitution levels of whey proteins. During storage, there was a low significant increase of energy input values

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