Vj. Savoie et Sd. Arntfield, EFFECT OF PH AND CATIONS ON THE THERMALLY-INDUCED GELATION OF OVALBUMIN, Journal of texture studies, 27(3), 1996, pp. 287-306
The gelation of ovalbumin in the presence of salts containing Ca+2 and
Mg+2 at various pH values was investigated. Characteristics of the ge
ls produced were evaluated using penetration measurements on an Ottawa
Texture Measuring System as well as dynamic rheology on a Bohlin VOR
rheometer. Gel properties were related to cation binding (equilibrium
dialysis) and to changes in protein structure (differential scanning c
alorimetry). Cation binding generally increased with increasing salt c
oncentration, and Mg+2 bound to a greater extent than Ca+2 at the high
er levels studied. The impact of this binding on gel structure was dep
endent on pH and the technique used to evaluate structure. At pH 5 pro
teins tended to coagulate regardless of the type or amount of salt. At
pH 7, the highest rigidity values from penetration measurements were
obtained at salt levels of 0.005 M. At pH 9, the salt concentration fo
r maximum rigidity varied with the salt, while the storage moduli (G')
from dynamic rheology were highest at the highest salt concentration
used. Based on rigidity data, the inclusion of 0.005 M MgSo(4) would g
ive a product with the greatest rigidity over a wide pH range.