title: Casein maps: effect of ethanol, pH, temperature, and CaCl2 on the particle size of reconstituted casein micelles.
abstract: 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 10mM 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 (0.25mg/mL) and calcium (20mM) caused the formation of larger aggregates (>1,000 nm) in the presence of ethanol when comparing with the initial lower concentrations of casein (0.1mg/mL) and calcium (2mM). Casein micelle dissociation can be achieved near the isoelectric pH by modifying the solvent composition and temperature.
authors.affiliation: Department of Food Science and Technology, University of Tennessee, 2605 River Road, Knoxville, Tennessee 37996-4539, USA.
authors.forename: Ran
authors.initials: R
authors.lastname: Ye
authors.forename: Federico
authors.initials: F
authors.lastname: Harte
mesh_terms: D002122:Calcium Chloride / Q000494:pharmacology; D002364:Caseins / Q000187:drug effects / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D005524:Food Technology / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D010316:Particle Size; D013696:Temperature
chemical_list: D002364:Caseins; D008823:Micelles; D000431:Ethanol; D002122:Calcium Chloride