Denaturation and Viscosity of Whey Proteins Solutions as Affected by Frozen Storage

Concentrated solutions of whey proteins (WPC) were prepared from sweet whey by ultrafiltration technique, and stored at – 18°C up to three months. Denaturation degree and viscosity of WPC solutions were assessed. Denaturation degree of whey protein solutions increased significantly (P<0.05) as affected by duration of frozen storage and protein content. The highest degree of denaturation was found at pH 5.0 and 7.0 after one month of storage. Denaturation percentages of heated and thawed WPC solutions increased significantly (P<0.05) as function of storage, protein content and pH. The flow properties of unheated WPC solutions exhibited a timeindependent non-Newtonian behaviour as shear-thickening (dilatants) properties with an increase in the apparent viscosity with increasing the shear rate. Heated thawed WPC solutions behaved as thixotropic fluids with a decrease in the apparent viscosity with increasing shear rate. Apparent viscosities of unheated and heated WPC solutions greatly affected by frozen storage, protein content and pH. [Journal of American Science. 2010;6(12):49-62]. (ISSN: 1545-1003).