The water activity of carrageenan gels with incorporated solutes was determined by cryoscopic osmometry. Kappa (k), kappalambda (kλ) and iota (κ) carrageenan were utilized at concentrations of from 0.1 2% solids producing a sol, viscous sol, and gel. The solutes used were sucrose, NaCl, Na2SO4, KCl, NH4Cl and urea at concentrations ranging from 0.05–1.0 kinetic units per kg H2O. All the solutes were found to give aw values as measured cryoscopically withhin 0.0005 units of literature values. The water activity of pure carrageenans at 0.1–2% solids was greater than 0.999. Addition of some solutes increased the water binding of the carrageenan‐solute‐water system as was found by a lower aw than expected. This interaction effect increased with increasing concentration of solute and carrageenan and was greater for solutes with lower activity coefficients. The interaction effect increased in the following order: Na2SO4, NaCl, KCl, and NH4 Cl. The force required to rupture the gel was measured using the Instron Universal Testing Machine. Solutes were found to influence the gel strength of k and kλ carrageenans, but not ι carrageenan. The solutes increased kλ carrageenan's gel strength in increasing order: urea, sucrose, Na2SO4, NaCl, NH4Cl, and KCl and k carrageenan's gel strength in increasing order: sucrose, Na2SO4 and NaCl. There appears to be no simple relationship between gel strength and water‐binding when solutes are added to carrageenan.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of food science|
|State||Published - May 1981|