Effects of Phosphorylation on Emulsifying and Foaming Properties and Digestibility of Yeast Protein

Phosphorylated yeast protein (PYP) (73% protein, < 3% nucleic acid) was prepared from yeast nucleoprotein by chemical phosphorylation using phosphorus oxychloride. The emulsifying activity index (EAI) of PYP was low at pH 5 but exceeded that of BSA at pH 7.0. The emulsions were stable after heating to 90°C for 60 min. The stability of foams made with PYP increased from t 1/2 1.5 to 13 min as pH was increased from 5 to 8. Foams made from PYP were weak but increased with protein from 0.1 to 0.5 mg/100 mL. The PYP were easily digested by pepsin and pancreatin indicating negligible inhibition by phosphorylation.