65A-36

M. A. KENAWI, Dept. of Food Science, Faculty of Agriculture, El-Minia University, El-Minia, 6111, Egypt

Most vegetables require a short heat treatment or blanching to inactivate enzymes and stabilize quality prior to and during frozen storage. Since conventional blanching processes using rapidly boiling water as a heating medium could cause leaching of solids and an ultimate loss of product, a more gentle blanching process with more efficient heating could have positive effects on the yield and quality of the finished product.

Microwave blanching has been identified as possessing such potential. Blanching freshly picked vegetables in a microwave not only speeds the freezing process but also maintains the foods nutritional value better than traditional blanching does. The objective of this study is to examine the effect of three methods of blanching (hot water, steam, and microwave) on some chemical changes, and sensory properties of three selected vegetables (potatoes, spinach, and cauliflower). Enzyme activity was evaluated to determine the time required completing the blanching of the different vegetables. Retention of vit. C and some minerals (Na, K, Ca, P, and Fe) were determined by HPLC and Atomic absorption respectively.

The sensory evaluation related to color, texture, and overall acceptability was evaluated. The result showed that microwave blanching had the shortest time required inactivating enzymes in the three selected vegetables. It was also found that the retention of vit. C and the minerals studied were generally higher in microwave blanching compared to the other methods. In addition, the sensory quality of microwave blanching was better than the two other methods.