Preparation of Casein Using Carbon Dioxide

¹ Agricultural Research Service, USDA, Eastern Regional Research Center, Engineering Science Research Unit, Philadelphia, PA 19118

The effects of pressure, temperature, residence time, and mass of skim milk on some characteristics of casein, prepared by precipitation with high pressure CO₂, were examined in a batch reactor. For a 500-g milk sample, precipitation occurred at pressures >2760 kPa and temperatures >32°C. Residence time was not significant and was held at 5 min.

Yields were maximum at 2750 to 5520 kPa and at 38 to 49°C for a 500-g milk sample. The resulting whey had a pH of 6.0. The casein product had an acceptable appearance and had greater solids, ash, and Ca contents than commercial acid caseins. Particle size distribution studies showed that the mean particle size was sensitive to precipitation pressure and temperature and was similar to that of acid caseins produced under laboratory conditions.

The HPLC studies of the casein and whey fractions showed that precipitation by CO₂ did not result in fractionation of casein or whey proteins to their component proteins.

Key Words: supercritical carbon dioxide • casein • whey • high pressure

Submitted on December 22, 1993
Accepted on October 24, 1994

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