Functionality of Casein Precipitated by Carbon Dioxide1

The functionality of casein that was precipitated by batch by a novel process using CO2 was investigated for solubility in water and NaCl, foam stability, overrun, emulsion activity index, and emulsion stability. These properties were compared with those of acidified casein and Na caseinate prepared in the laboratory, commercial acid casein, and commercial Na caseinate and Ca caseinates. The pH of the CO2 casein was 6.61 in water and 6.51 in 0.1 M NaCl; only 65.5% of the casein dissolved in water, which was significantly less than the 97.5% that dissolved in NaCl. The precipitated casein had better foam stability (29 min instead of 1 to 20 min) than did the other caseins, although the percentage overrun was lower (397% compared with 511 to 868%; 15-min whipping time). Emulsion stability (222 min) and emulsion activity index (56 m2/g) of the precipitated casein were not significantly different from those of caseins prepared in the laboratory but were significantly different from those of commercial caseins. All properties except foam stability were not significantly affected by variations between batches or days. The precipitated casein had functional properties that were significantly different from caseins and caseinates that were produced commercially or in the laboratory. (