市販ホウレンソウのL-アスコルビン酸および硝酸塩含量の周年変動(普及・教育・利用)  [in Japanese] Seasonal Variation of L-Ascorbic Acid and Nitrate Content of Commercially Available Spinach(Human Issues in Horticulture)  [in Japanese]

1. 京都府綾部市において, 2003年6月〜2004年5月までの1年間に毎月2〜3回の間隔で購入した市販のホウレンソウ(合計127サンプル)に含まれるL-アスコルビン酸(AsA)と硝酸塩の周年変動を調査した.2. AsA含量は, 夏期(7月〜8月)に低く冬期から春先(1月〜3月)にかけて高い傾向が認められた.また, この傾向は可食部上部(葉身側)で特に高かった.3. 硝酸塩含量は, 7月〜9月に高く, 1月〜3月に低い傾向が認められた.また, この傾向は可食部下部(葉柄側)で顕著であった.4. 生体重および葉色(SPAD値)と2つの品質成分(AsA含量と硝酸塩含量)との間に有意な相関が認められたが, これらの相関関係は外観形質から品質成分の多寡を推定するには十分ではないと判断された.

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.