Antioxidant activity and quality of asparagus affected by microwave-circulated water combination and conventional sterilization

Green asparagus (Asparagus officinalis L.), as a healthy and perishable vegetable, is processed after harvest to minimize the deterioration of its physical and chemical quality. In our research, fresh asparagus was sterilized using several methods, including a pilot-scale 915 MHz microwave-circulated water combination (MCWC) heating system, pressured hot-water heating and steam-heating in a retort. Rutin content of asparagus processed by these methods did not show significant difference. But antioxidant activity of asparagus after MCWC treatment was significantly greater than that processed by other methods. Although the shear stress of asparagus spears was significantly decreased by eight times after sterilization, no significant difference existed among the textures of asparagus processed by these methods. Asparagus processed by MCWC showed greener colour with negative a* value and greater hue value (H⁰) than did hot water- and retort-treated asparagus. Therefore, asparagus sterilized by MCWC showed greater antioxidant activity and greener colour than did asparagus processed by the conventional methods.