Abstract
The seasonal variations of L-ascorbic acid and nitrate concentration in spinach purchased at a market in Ayabe city, Kyoto pref. were investigated. Spinach samples were purchased from the market 2-3 times per month between June 2003 and May 2004, and the L-ascorbic acid and nitrate concentrations were measured using an RQ flex system. The L-ascorbic acid concentration was relatively low in summer (Jul.-Aug.), and relatively high from winter to early spring (Jan.-Mar.). A clear increase in the L-ascorbic acid concentration was observed from winter to early spring, due to an increase in L-ascorbic acid concentration in the upper half (blade side) of the edible part. The nitrate concentration was relatively high in summer (Jul.-Sep.), and relatively low from winter to early spring (Jan.-Mar.). A clear increase in the nitrate concentration was observed in summer, which was due to an increase in the nitrate concentration in the lower half (petiole side) of the edible part. There was a correlation between the external factors (leaf color and other aspects) and the two internal factors (L-ascorbic acid and nitrate concentrations). However, this correlation was insufficient to assume the two internal factors based on external factors.
