Limited Enzymatic Treatment of Skim Milk Using Chymosin Affects the Micelle/Serum Distribution of the Heat-Induced Whey Protein/κ-Casein Aggregates

• Published in: Journal of agricultural and food chemistry 2007-08, Vol.55 (16), p.6736-6745
• Main Authors: Renan, Marie, Guyomarc'h, Fanny, Chatriot, Marc, Gamerre, Valérie, Famelart, Marie-Hélène
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Caseins - analysis; Caseins - chemistry; chymosin; Chymosin - metabolism; enzymatic treatment; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; heat treatment; Hot Temperature; Hydrolysis; kappa-casein; Life Sciences; Micelles; Milk - chemistry; Milk - metabolism; Milk and cheese industries. Ice creams; Milk Proteins - analysis; Milk Proteins - chemistry; Particle Size; protein aggregates; proteolysis; rennet; renneting; skim milk; whey protein; Whey Proteins
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0705771

The effects of heat treatment and limited κ-casein hydrolysis on the micelle/serum distribution of the heat-induced whey protein/κ-casein aggregates were investigated as a possible explanation for the gelation properties of combined rennet and acid gels. Reconstituted skim milk was submitted to combinations of 0−67% hydrolysis of the κ-casein at 5 °C and heat treatment at 90 °C for 10 min. The protein composition of the ultracentrifugal fractions was obtained by reverse-phase high-performance liquid chromatography (RP-HPLC). The aggregates contained in each phase were isolated by size-exclusion chromatography and analyzed by RP-HPLC and sodium dodecyl sulfate−polyacrylamide gel electrophoresis. Upon heating only, 20−30% of the total κ-casein dissociated, while 20−30% of the total whey protein attached to the micelles. When heated milk was renneted, little changes were observed in the distribution and composition of the aggregates. Conversely, the heat treatment of partially renneted milk induced the formation of essentially micelle-bound aggregates. The results were discussed in terms of the preferred interaction between hydrophobic para-κ-casein and denatured whey proteins. Keywords: Milk; heat treatment; chymosin; whey protein; κ-casein