Abstract: The physicochemical properties and antioxidant activity in vitro of selenium-enriched pea seedling powders produced by hot air drying or freeze drying were studied. The effects of different drying processes on the percentage loss of organic selenium content, color, microstructure, water distribution and antioxidant activity in vitro of pea seedling powder were investigated by chemical analysis and instrumental analyses using colorimeter, scanning electron microscopy (SEM) and low-field nuclear magnetic resonance (NMR). The results indicated that the product prepared by hot air drying at 100 ℃ had desired quality with a small percentage loss of organic selenium of 36.7% and good color. Selenium-enriched pea seedling powder consisted of blocky particles with more wrinkled surface and a larger number of fiber bundles compared with ordinary pea seedling powder. There were significant differences in water distribution between Se-enriched and non-Se-enriched pea seedling powder prepared by hot air drying. Compared with non-Se-enriched pea seedling powder, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capacity (half maximal inhibitory concentration IC50 = 0.61 mg/mL), hydroxyl free radical scavenging capacity (IC50 = 0.86 mg/mL), superoxide anion radical scavenging capacity (IC50 = 0.90 mg/mL) and ferric reducing power (absorbance value = 0.30) of the ethanol extract from Se-enriched pea seedling powder were significantly higher (P < 0.01). These results provide theoretical guidance and a technical reference for the development of organic selenium supplements and the industrialization of selenium-enriched foods.

Key words: selenium enrichment; pea seedling powder; drying methods; physicochemical properties; antioxidant activity