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KMID : 0380620160480010015
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Korean Journal of Food Science and Technology
2016 Volume.48 No. 1 p.15 ~ p.19
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Enhancement of Antioxidant Activity of Onion Powders by Browning during Drying Process
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Lee Dong-Jin
Han Jung-Ah
Lim Seung-Taik
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Abstract
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Drying process was applied to increase the antioxidant activity of onion powder: freeze-drying or air-drying at 50, 70, and 90°C and onion extracts were obtained from each powder using water or aqueous ethanol (50%) at 25°C and 60°C. In the color analysis, the freeze-dried powders showed higher L* and lower a* and b* values than did the air-dried ones. The browning index of powders air-dried at 90°C was significantly higher than that of freeze-dried powders or those air-dried at temperatures below 90°C. Phenolic content in the extracts was 4.02-23.12 mg gallic acid equivalent/g sample, and was the highest in the extract from the sample air-dried at 90°C, regardless of the extraction condition. The highest antioxidant activity, measured by 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid and 1,1-diphenyl-2-picrylhydrazyl methods, was found in the powder air-dried at 90°C, which induced browning. These findings indicate that antioxidant activity depends more on browning during drying than on extraction conditions.
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KEYWORD
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onion powder, air-drying, browning index, phenolic content, antioxidant activity
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