Whey protein isolate (WPI) was provided by Davisco Foods International Inc. (Le Sueur MN). The WPI was reported to contain 97.9 wt.% protein and 0.2 wt.% fat. Corn oil was purchased from a local supermarket. The following chemicals were purchased from the Sigma Chemical Company (St. Louis, MO): β-carotene; alginic acid (sodium salt); mucin from porcine stomach; pepsin from porcine gastric mucosa; lipase from porcine pancreas; porcine bile extract; and Nile Red. All chemicals used were analytical grade. Double distilled water was used to make all solutions.