Prior to the introduction of MPC, WPC was commonly used throughout the yogurt industry as the functional protein ingredient to increase yogurt gel strength and decrease gel syneresis (wheying off). A number of dairy industry studies throughout the years have found an increase in yogurt gel strength and a decrease in syneresis in WPC-fortified yogurts as compared to yogurts manufactured from 100% milk. This result isn’t all that surprising because as WPC is added to yogurt milk, the total solids of the milk, as well as the protein content of the milk, is increased. As yogurt total solids and protein content increase, increased gel strength and decreased syneresis result. WPC is from a dairy origin and, therefore, thought to be an ingredient with better consumer appeal, compared to other commonly used stabilizers—“modified foodstarch,” “pectins,” and/or “gelatins.” As a result, many yogurt manufacturers have added WPC to their yogurt as a stabilizing ingredient. As WPC usage in yogurt increased, however, it became apparent that there were limitations as to how much WPC could be added to yogurt formulations before significant sensory defects were encountered. Addition of WPC to yogurt milk results in a yellowish color which intensifies with increasing WPC levels. Excess levels of WPC in yogurt can cause the otherwise smooth yogurt gel to turn grainy, thereby lowering consumer acceptance. Excess levels of WPC were also found to adversely affect yogurt aroma and flavor, resulting in a sensory profile that is not considered normal for yogurt and can cause consumer rejection.
To overcome the issues encountered with use of WPC in yogurt, researchers began using MPC to blend with WPC or totally replace WPC in yogurt applications. Use of MPC results in a more realistic gel texture compared to WPC. Use of MPC in yogurt does not negatively impact the flavor or aroma of yogurt as does WPC. On the other hand, recent studies have demonstrated that yogurt containing WPC may display increased gel strength compared to yogurts containing MPC. Therefore, researchers feel that a blend of MPC and WPC (predominately MPC) may work best in yogurt applications. Use of a blend in which the MPC content is about 80% of the blend (compared to 20% WPC) will yield a yogurt with increased gel strength and decreased syneresis while maintaining desirable sensory properties.