Color and gelling properties of dried egg white: Effect of drying methods and storage conditions

Dried egg white is extensively used as a food ingredient due to its unique functional properties and extensive shelf life. This study investigated the effect of drying methods and storage conditions on the color and gelling properties of dried egg white. Egg white was dried with two drying methods; freeze drying and hot-air drying, then stored at 25 and 40 degrees C for 4 months. The result showed that the color of hot-air-dried egg white, especially after storage at 40 degrees C, was darker yellow than for freeze-dried egg whites. The gelling properties of both samples were altered during storage, however, substantial changes in the gelling properties were found in the gel made from stored hot-air-dried egg white. A decrease in the enthalpy of protein denaturation that indicated a partially unfolded protein conformation, an increase in exposed sulfhydryl and a decrease in the total sulfhydryl contents were found, especially in stored samples of hot-air-dried egg whites. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern of proteins in the stored samples showed protein aggregation, and this was related to the increased glass transition temperature. This study revealed that drying egg white using hot-air drying and storage especially at high temperature induced changes in their color and protein conformation. These have contributed to protein aggregation which affected dried egg white's gel properties.