Effect of phospholipase C papain on feathering defect in 11% homogenized UHT processed cream

Abstract

Commercial creamers that did and did not demonstrate feathering defect showed differences in feathering test, phospholipid proportion, and protein patterns of surface material of homogenized fat globules. Creams that did not feather were stable pH at in acetate buffer as low as 5.00; creams that did exhibit feathering defect were stable in acetate buffer at pH of 5.45 and higher. The proportion of phosphatidylethanoamine in feathering cream was higher than in stable cream while the proportions of phosphatidylinositol and phosphatidylserine in feathering cream were slightly less than in stable cream. Feathering cream had more caseins associated with milk fat globule than stable cream and more protein bands were observed in feathering cream than in stable cream.

Feathering test with a series of acetate buffer solutions of different pHs revealed that papain treatment of cream (0.075 EU/ml) induced feathering defect near pH of 5.60 while phospholipase C treatment of cream (0.75 EU/ml) did not cause coagulation of protein and fat globules at pH 5.09. Papain-treated cream flocculated in coffee with pH 4.56 at 85°C but phospholipase C-treated cream did not. Small activity (0.075 EU/ml) of sulfhydryl protease (papain) in cream degraded most casein associated with newly formed membrane into small peptides when incubated at 4° and 21°C for 1 day. One of milk fat globule membrane proteins (butyrophilin) was hydrolyzed by papain while β-lactoglobulin was not degraded in papain-treated cream About 65-70% of phospholipid in the membrane material was degraded when 0.75 EU of phospholipase C was inoculated to 11% homogenized UHT processed cream and incubated at 4 and 21°C for 14 days. Major phospholipids (phosphatidylcholine, phosphatidylserine, phosphatidylinositol, and phosphatidylethanolamine) were hydrolyzed by phospholipase C while sphingomyelin remained intact. Heat treatment of whey protein at 80°C for 7 minutes to cover newly formed fat globule did not prevent the feathering problem in papain-treated cream.