Abstract: Raw soybean does not have vitamin C, but it can generate vitamin C during the germination process. Moreover, the content of vitamin C reveals an increase with prolonged germination time. The content of vitamin C was measured by 2,6-dichlorophenol indophenol method and the effects of exogenous factors such as glucose, L-galactose, D-mannose, potassium iodide and UV irradiation on vitamin C were explored. The results showed that glucose, L-galactose, potassium iodide and UV irradiation could accelerate the synthesis of vitamin C. L-galactose treatment revealed the most obvious effect on the content of vitamin C, resulting in an increase of 8.43 mg/100 g when compared with untreated soybean. Similarly glucose treatment also exhibited a stronger effect on the content of vitamin C, which was improved by 4.23 mg/100 g. Prolonged soaking in these solutions at a lower concentration was better than short-time soaking in these solutions at a higher concentration. Moreover, UV irradiation on the 5th day could obviously accelerate the synthesis of vitamin C.

Key words: soybean, germination, exogenous factors, vitamin C content