The Effects of Microwave Blanching Conditions on Carrot Slices: Optimization and Comparison

Abstract The objectives of this study are (1) to determine conventional blanching ( CB ) conditions providing 100% peroxidase ( POD ) inactivation and adapt these inactivation conditions to microwave blanching ( MB ) for inactivating pectin methylesterase ( PME ); (2) to optimize the MB conditions by response surface methodology to ensure almost 100% PME ; and (3) to compare the properties of samples at the optimum points with those of conventional blanched and unblanched carrot samples. CB conditions were found to be 300 s with 150 mL of blanching water at 94C. MB conditions of samples have been optimized by using independent variables: microwave power (360–900  W ), blanching time (10–300 s) and blanching water volume (0–150 mL). Three optimum points were determined: (1) 900  W  − 170 s − 75 mL water; (2) 630  W  − 190 s − 75 mL water; and (3) 360  W  − 300 s − 75 mL water for MB . PME inactivation ratio was determined as almost 100% optimum points. Therefore, pectin was highly retained, carotenoid contents and color values were better protected as well. In summary, 360  W /300 s/75 mL water conditions were found to be optimum for blanching of carrots. Practical Applications Nowadays, the food industry focuses on novel treatments for inactivating enzymes with minimum deleterious effects on texture, flavor and nutrients. Blanching is one of the preprocessing steps before canning, drying and freezing of vegetables. Blanching treatment also stabilizes color, texture, flavor and nutritional quality of the products, as well as inactivates peroxidase and pectin methylesterase which catalyzes deleterious changes. Microwave heating is a very popular food processing technique and can be utilized as an alternative to water blanching. This study explored whether microwave blanching can be used for enzyme inactivation, which, in turn, requires less processing time and water with minimal loss of quality.