SORPTION OF WATER VAPOR AND OF NITROGEN BY GENETIC VARIANTS OF ALPHAS1-CASEIN

Water vapor sorption by dried preparations of αs1-caseins A and C was measured at 24.2°. At lower relative pressures, both forms sorbed identical amounts of water, while at intermediate to higher relative pressures the A variant sorbed more water. A reproducible hysteresis loop was observed over the entire isotherm through two successive sorption-desorption cycles. Treatment of the H2O sorption data and nitrogen adsorption data according to the Frenkel-Halsey-Hill isotherm equation allowed for clear distinction between the natures of the sorption processes involved with H2O and N2.