CHEMICAL AND FUNCTIONAL PROPERTIES OF CRYACASEIN (RENNET COAGULATION)
Abstract
Casein was isolated from skim milk by ultrafiltration and cryodestabilization. The resultant product, cryocasein, was resuspended in water using agitation and mild heating. Research was conducted to investigate the chemical properties of cryocasein, and to assess its functionality. Cryocasein contained higher ash and lactose content than commercial casein and caseinate products. As compared to acid casein, cryocasein had a slightly lower (beta)-casein content due to the preparation procedures involving low temperatures and ultrafiltration. Retainment of micellar structure was verified by electron microscopy and permeation chromatography on CPG-10. An increase in aggregation of casein micelles was observed during frozen storage (-8(DEGREES)C) of diluted ultrafiltration retentate. Similar to skim milk, this intact micellar structure may be responsible for properties such as solvation and stability towards addition of ethanol and Ca('2+). Solubility of cryocasein was considerably affected by pH and ionic strength, possibly due to their effects on the integrity of the colloidal calcium phosphate structure. Emulsifying properties of cryocasein were not as good as those of sodium and calcium caseinates, suggesting that micellar structure was not of advantage in functional applications which require surface activity. However, cryocasein retained the ability, similar to native casein micelles in milk, to form a curd upon rennet addition. Cryocasein curd was firmer and showed less syneresis than the curds from calcium caseinate and sodium caseinate. Considering its redispersibility, stability to calcium addition, and rennet coagulability, it is suggested that cryocasein may be utilized as a food ingredient either by itself or in combination with other proteins for certain functional applications.
Degree
Ph.D.
Subject Area
Food science
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