Premium
Scaling approach to water sorption isotherms of hydrogels and foods
Author(s) -
Mizrahi Shimon,
Ramon Ory,
SilberbergBouhnik Miriam,
Eichler Sigal,
Cohen Yachin
Publication year - 1997
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 - 10.1046/j.1365-2621.1997.00379.x
Subject(s) - sorption , osmotic pressure , scaling , self healing hydrogels , swelling , water activity , counterion , thermodynamics , chemistry , polymer , chemical engineering , adsorption , polymer chemistry , ion , organic chemistry , water content , biochemistry , physics , geology , geotechnical engineering , mathematics , geometry , engineering
Mechanisms affecting water sorption isotherms of foods, at high water activities, were evaluated by the processes of swelling and shrinking of model systems of uncharged and charged hydrogels. Their water activity was found to be determined by the combined effect of their osmotic pressure and the network pressure of the polymeric network. The scaling approach in polymer science indicates that in an uncharged network the osmotic pressure is affected by the mobility of the polymer segments and thus by the degree of cross‐linking. However, in charged gels, which behave in a similar manner to many food systems, the counterions play the dominant role in determining the osmotic pressure. The network pressure may shift from a positive to a negative value during shrinking (dehydration), thus counteracting or co‐operating with the osmotic pressure in decreasing the water activity. A scaling sorption isotherm, at high water activity, is formulated for a food system with physically significant parameters.