The research was carried out at the Department of Food, Bioprocessing, and Nutrition Sciences, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh.
Flavor is one of the key factors that can limit the application and shelf life of dried dairy ingredients.
In the study, WMP was produced from standardized pasteurized whole milk that was evaporated to 50% solids, homogenized in two stages with varying pressures, and spray dried.
WMP was then evaluated at zero, three, and six months of storage at 21°C.
Due to its higher fat content, lipid oxidation in WMP occurs more readily than in nonfat dry milk.
The flavor of WMP produced in the US is highly variable, the authors said, with lipid oxidation being the main source of off-flavors.
Increased free fat has been associated with increased lipid oxidation in dried dairy ingredients.
Decreasing free fat by homogenization
During WMP manufacture, homogenization decreases the fat globule size, which also decreases the migration of fat to the surface of WMP.
Increased homogenization pressures have been reported to increase the amount of protein on the surface of the milk fat droplets in condensed whole milk. The increased protein on the surface of these droplets, along with the smaller size due to homogenization, decreases the amount of free fat in the spray-dried WMP.
The authors said increased homogenization pressure decreased ‘cardboard’ and ‘painty’ flavors, volatile lipid oxidation compound concentrations, fat globule size in condensed milk, surface free fat, and inner free fat in WMP.
The reduction in off-flavors was due to the decrease in free fat, the researchers concluded.
Smaller fat globule size is key
The researchers said their results indicated WMP flavor stability was improved with increased homogenization pressure and decreased fat globule size in the condensed whole milk.
They said WMP manufacturers should continually evaluate the effectiveness of their homogenizer to improve the flavor and shelf life of their product with the goal of smaller fat globule size in their condensed whole milk.
Funding was provided in part by the National Dairy Council.
Source: Journal of Dairy Science
The effect of homogenization pressure on the flavor and flavor stability of whole milk powder
Authors: Curtis W. Park, MaryAnne Drake