Gelation property and water holding capacity of heat-treated collagen at different temperature and pH values

Gelling properties and water holding capacity of collagen were evaluated from the hydrolysis of this protein at different conditions of temperature (50, 60 or 80 degrees C) and pH (3, 5, 7 or 10) during 6 h. In addition, soluble protein content, surface charge, molecular weight distribution and denaturation temperature of collagen processed at different conditions were analyzed. The products showed soluble protein content between 5 and 82% (w/w), but higher values were obtained from the treatments carried out at the highest temperature and pH below isoelectric point (pI). The pI decreased as the hydrolysates were produced at lower acidity and also with increasing intensity of the heat treatment. Products obtained under extreme conditions of pH (3 and 10) or temperatures above or similar to the collagen denaturation temperature (80 and 60 degrees C) were completely denatured as observed by differential scanning calorimetry. In addition, electrophoresis analysis showed that the mean molecular weight decreased at acidic pH and elevated temperature. In general, the hydrolysates obtained at acidic pH formed firmer gels, except that produced at the most intense conditions of heat treatment. Gels formed with hydrolysates obtained at other pH values showed low values of stress at fracture, indicating the formation of a structure more fragile and particulate. The water holding capacity (WHC) of gels was approximately 100%, except for hydrolysates obtained at a higher pH (7 and 10) and temperature above denaturation. (c) 2012 Elsevier Ltd. All rights reserved.