Quantitative and Crystal Change of Calcium Oxalate in Spinach by the Immersion in Boiling Water

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  • ISHII Yuuko
    Department of Home Science, Mukogawa Women's University;

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Other Title
  • 煮沸によるホウレンソウ中のシュウ酸カルシウム量と結晶の変化

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Changes of morphology and crystal structure of calcium oxalate in spinach by boiling in water were examined. Oxalic acid in spinach was extracted by 20 min' immersion in boiling water. Both of oxalic acid and calcium oxalate were extracted from spinach by one night's immersion in 0.1 M hydrochloric acid. The concentration of oxalic acid or that of the sum of oxalic acid and calcium oxalate in the extracts was determined by ion chromatography. From the difference between the above two concentrations, the quantity of calcium oxalate was obtained. Spinach (100 g) used in the present experiment contained 730 mg of oxalic acid and the sum of oxalic acid and calcium oxalate was 912 mg. Then calcium oxalate as dihydrate was calculated at 339 mg per 100 g of spinach. This sample was boiled for 8 hs and calcium oxalate remaining in spinach was obtained every one hour. The quantity of calcium oxalate decreased, which was more pronounced after 4 hs. After 8 h' boiling, about 26% calcium oxalate disappeared. After one hour's boiling, small holes and cracks began to appear on the surfaces of calcium oxalate crystals. After more than 8 h boiling, samall crystals of calcium oxalate monohydrate appeared on the surfaces of the initial crystals and X-ray diffraction showed that a half of calcium oxalate crystals in spinach changed into calcium oxalate monohydrate.

Journal

  • NIPPON KAGAKU KAISHI

    NIPPON KAGAKU KAISHI 1991 (4), 316-320, 1991-04-10

    The Chemical Society of Japan

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