Hydration of Native and Rennin Coagulated Caseins as Determined by Differential Scanning Calorimetry and Gravimetric Sorption Measurements

Abstract

Differential Scanning Calorimetry and an automatic sorption apparatus were used to study hydration of native caseins and rennin coagulated caseins (para- caseins). Similar to other protein-water systems, determination of the heat and temperatm-e of fusion of the adsorbed water allowed resolution of the water into four states. For both native, and para- casein the amounts and thawing intervals for the different water fractions were not significantly different. However, the ad- sorption and desorption isotherms and the differential sorption rates were dif- ferent for native and freshly coagulated paracasein. Paraeasein did not alter water binding capacity when syneresis was induced. From the water sorption data and structural features of native- and paracaseins one may conc!ude that changes in the water binding capacity play only a minor role in the secondary phase of casei~ eo~gu!ation bv rennin and that the phenomenon of syneresis is not accompanied bv changes in the na- ture of hydration.