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Determining Protein Content of Ice Cream and Frozen Desserts¹

Department of Food Science, The Pennsylvania State University, University Park 16802

ABSTRACT

Dye binding of protein is a suitable, rapid, and relatively inexpensive method for the determination of protein in ice cream and frozen desserts. The presence of proteins with reduced amounts of basic amino acids will depress protein percentage slightly as measured by dye binding. Proteins with higher percentages of basic amino acids tend to increase apparent protein content. At this time, only noncolored ice cream is recommended for protein testing by dye binding because of the influence of coloring matter on test results. The effect of food coloring was studied with model systems of milk and 2% food color solutions. With amido black, dye binding values (protein percentages) were depressed increasingly by yellow to red to green to blue dyes. With orange G dye, the effect on protein results was decreased from yellow to green to blue to red. Also, protein percentages decreased with increased concentration of food color. Overall, results with amido black dye binding procedure were less affected than protein readings with orange G. Colored dairy products can be tested accurately for protein by dye binding if the nature and concentration of the added food color are known. A factor then must be determined to enable conversion from dye binding value to protein content.

¹ Authorized for publication as Paper No. 5344 in the journal Series of the Pennsylvania State University. The work was partially supported by a grant-in-aid from Dairy Research Inc., Rosemont, IL.