SUPPLEMENTAL LIGHT ENHANCES POLYPHENOL CONTENT AND ANTIOXIDATIVE CAPACITY OF BROCCOLI SPROUTS GROWN IN AN INDOOR PRODUCTION SYSTEM

Brassica sprouts have become familiar to consumers as a healthy vegetable because of not only their basic nutritional traits but also their biological and pharmacological activities. The objective of this study was to evaluate the influence of supplemental light on the polyphenol content and antioxidative activity of broccoli sprouts grown on a commercial scale. Broccoli sprouts (B. oleracea var. italica) were grown for four days under various lengths of supplemental white fluorescent light (20–100 μmol m^-2 sec^-1) in an indoor sprout production system equipped with additional light supplying devices we developed. Both polyphenol content and DPPH radical absorbing activity significantly increased in relation to the duration of the supplemental light. Meanwhile, hypocotyl lengths were significantly shortened by two days or more of supplemental light. The effects of a combination of different wavelengths of light sources were also evaluated. Forty eight hours of additional light supply in the following two types of combinations: (1) white fluorescent light and black light (UV-A); (2) red fluorescent light and black light, significantly enhanced polyphenol content, while showing much less effect in shortening hypocotyl lengths. These results suggest that supplemental white light combined with UV-A light brings about an increase of polyphenol content and the enhancement of antioxidative activity in broccoli sprouts with only very little effect on shortening hypocotyl length.