Effects of Soaking pH and Extracting Temperature on the Physicochemical Properties of Chicken Skin Gelatin

This study was conducted to evaluate the effects of soaking pH and extraction temperature on the physicochemical properties of chicken skin gelatin. In order to extract gelatin from chicken skin, the chicken skin was soaked at various pH ranges (1-13) and was extracted at 75 and $100^{\circ}C$. For the rate of weight increase, the highest value was obtained from two pH ranges (1-2 and 12-13). In addition, the rate of weight increase was affected by soaking time. The alkali treatments had greater crude protein content as well as total extraction yield compared to the acid process (p<0.05), and the increased extraction temperature resulted in a significant (p<0.05) increase of crude protein content and total extraction yield. All treatments showed ${\alpha}1$ and ${\alpha}2$ chains derived from type I collagen on SDS-PAGE. The pH value and color of gelatin gel (6.67%) were affected by soaking pH and extraction temperature. Chicken skin gelatin gel extracted at $75^{\circ}C$ after soaking at a pH of 2 had the highest melting point (p<0.05) and gel strength among all treatments. Although the chicken skin treated with the alkali process had a higher yield, a lower extraction temperature following the acid process would be better for obtaining superior gelatin from chicken skin.