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Effect of water content on the mobility of solute molecules and of protein side chains in casemate preparations
Author(s) -
MESTE MARTINE LE,
DUCKWORTH R. B.
Publication year - 1988
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.1988.tb00602.x
Subject(s) - chemistry , nitroxide mediated radical polymerization , side chain , water content , solvent , bound water , molecule , thermal diffusivity , casein , covalent bond , properties of water , chemical physics , electron paramagnetic resonance , chemical engineering , organic chemistry , thermodynamics , nuclear magnetic resonance , polymer , physics , geotechnical engineering , radical polymerization , engineering , copolymer
Summary The effect of water content on the mobility of small solute molecules and of casein side chains was studied by electron spin resonance in caseinate/water systems. The immobilization of nitroxide probes of different sizes and properties were followed during progressive dehydration of concentrated caseinate preparations (3 g H 2 O/g dry protein). Above a characteristic minimum moisture content a linear relationship was observed between the rotational diffusivity and water content. The slope of the straight lines depended upon the size of the probe and upon the nature of the interactions with the protein. Nitroxide labels were covalently bound to caseinate and the changes in the flexibility of the side chains as hydration changed were followed. The results are discussed in relation to the solvent properties of water, and to recent suggestions concerning the significance, for stability, of the glass transition phenomenon in such materials.