Although conditions favoring casein micelle aggregation are well known, factors promoting the dissociation of the casein micelle are not fully understood. It was our objective to investigate the ethanol-induced dissociation of micellar casein as affected by temperature and a wide range of pH, along with the concentrations of calcium and casein. Two different concentrations of casein micelles were dispersed in imidazole buffer with 0 to 80% ethanol (vol/vol) and 2 and 10. m. M calcium. Apparent micelle size was determined by dynamic light scattering at 5, 30, and 60°C. In the absence of ethanol, casein precipitation occurred at pH 4.6 in imidazole buffer. Ten to forty percent ethanol promoted casein aggregation (> 1,000. nm) and higher temperature (30 and 60°C) enhanced this effect. Higher ethanol concentrations at 50 to 80% induced the dissociation (< 40. nm) of the casein micelle upon acidification (pH < 5) and alkalization (pH > 8) in imidazole buffer. In addition, higher concentrations of casein (0.25. mg/mL) and calcium (20. m. M) caused the formation of larger aggregates (> 1,000. nm) in the presence of ethanol when comparing with the initial lower concentrations of casein (0.1. mg/mL) and calcium (2. m. M). Casein micelle dissociation can be achieved near the isoelectric pH by modifying the solvent composition and temperature.
All Science Journal Classification (ASJC) codes
- Food Science
- Animal Science and Zoology