Relation between Riboflavin and Carbohydrates in Uuhulled Rice during the Ripening Period of Rice Plant

Investigations on the relation between riboflavin and carbohydrates in unhulled rice during the ripening period were made using two rice varieties; Futaketori and Aikoku No. 1. In each variety, total riboflavin was aboundantly found in unhulled rice 10 days after heading, and was decreased rapidly around 35 days after heading, then the riboflavin level was constant. Free riboflavin dominated ca. 90% of total amount of riboflavin 10 days after heading, then the free riboflavin gradually decreased in its content in both varieties; Futaketori took 226 days and Aikoku No. 1. needed 223 days after heading to get 40% level. Both varieties showed a rapid increase in total sugar content during the first month after heading, then maintained a constant sugar content. The ratio of reducing sugar to total sugar and that of non-reducing sugar to total sugar were rapidly lowered during the period of 20 days. However, 60 days after heading, the ratios gradually decreased to less than 1%, and no change was noticed further. It seemed to be a negative correlation between starch and free riboflavin, but any particular relation among other component was not found.