Sorption Behavior of Mechanically Mixed and Freeze‐Dried Sucrose/Casein Mixtures

Interactions between sucrose and casein were investigated by adsorption isotherms. Mechanically mixed and freeze‐dried sucrose/casein mixtures at sucrose percentages of 1, 5, 10, 15 and 20% (wet basis) were compared to calculated isotherms using the mass balance equation, over the a_w range 0.23–0.93 at 20°C. The mechanical mixtures did not exhibit solute/polymer interactions. The freeze‐dried systems showed positive interaction (i.e., sorbed more water than calculated) for 1 and 5% sucrose at all a_w values. For the 10, 15 and 20% sucrose mixtures, positive interaction continued below 0.86 a_w; however, above 0.86 a_w, no interaction was apparent. That is, experimental sorption values equaled calculated values.