29D-22 |
The influence of thermal treatments on antioxidant activity of asparagus |
S. W. WANG1, J. R. Powers1, J. Tang2, and C. I. Nindo2. (1) Dept. of Food Science & Human Nutrition, Washington State Univ., PO Box 646376, Pullman, WA 99164-6376, (2) Dept. of Biological Systems Engineering, Washington State Univ., PO Box 646120, Pullman, WA 99164-6120 In the state of Washington, about 1.5 tons/acre of spears are left in the field and 40 to 45% of asparagus are rejected from canning process because of length, size, or damage. These rejected asparagus could still have high nutritional value and antioxidant activity. So, why not dry these rejected asparagus and increase the economic value of Washington asparagus. Our objective was to determine the effect of the thermal and drying treatments on antioxidant activity in asparagus. Asparagus spears were blanched in two methods: water blanching at 85oC for 3min and microwave blanching at microwave power 4.5 W/g for 3 min. Blanched asparagus spears then were cut into small pieces (2-4 mm) and dried at Microwave Spouted Bed (MWSB) drying system at microwave power 2 W/g at 60oC. The drying rate was measure by the weight loss of products every 10 min. The antioxidant activity of blanched and dried asparagus was measured using the ABTS/HRP decoloration method. Blanching resulted in asparagus weight loss: 14.7% weight loss for microwave blanched asparagus and 1.5% weight loss for water blanched asparagus. The antioxidant activity changed slightly after blanching and drying. After blanching, the antioxidant activity for water and microwave blanched asparagus spears were increased 7 and 26% compared to the raw spears. After drying, the antioxidant activity of water and microwave blanched asparagus decreased, but microwave blanched asparagus showed better antioxidant activity retention (95%) than water blanched asparagus (78%). These results demonstrate that thermal treatments do not have negative effect on antioxidant activity of asparagus. So, drying could be used as an °§added-value°¨ processing for asparagus. In addition, microwave blanching would be a better choice because it could maintain greater antioxidant activity than water blanching.
Session 29D, Food Engineering: Thermal processes
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