Determination of vitamins, polyphenols and minerals in roots and foliage of sweet potato (Ipomoea batatas (L) Lam)
1991
Koizumi, H. (National Food Research Inst., Tsukuba, Ibaraki (Japan)) | Yasui, A. | Suzuki, T. | Tsutsumi, C.
To utilize foliage of sweet potato (Ipomoea batatas (L.) Lam), the following subjects were investigated: a) Extraction of mineral components with acid and water, b) contents of vitamins, polyphenols and minerals in representative species, and c) changes in these components during growth. When a HCl-extract of foliage (Benikomachi via.) was neutralized and filtered by an ultrafiltration membrane, more than 80% of minerals were retained. However, 50% of nitrogen and 70% of calcium were not recovered. This suggests that calcium bound with proteins could not pass through the ultrafiltration membrane. About 60% of minerals in foliage could be extracted with water. However, only 4% of calcium could be extracted. The filtrate obtained by ultrafiltration of the aqueous extracts had about 40% of magnesium, copper and zinc in the original solution. Foliage of sweet potato (Beniazuma, Benihayato, Kanto-32, Koganesengan and Kokei-14 var.) contained 60-70mg/100g of vitamin C, 3-7mg/100g of alpha-tocopherol and beta-carotene. Alpha-tocopherol content of foliage of sweet potato was 1.5-3.5 times that of spinach. The vitamin C and calcium content increased along with growth. Amounts of other components were almost the same at different growth stages. No correlations between leaves and roots in contents of vitamins, polyphenols and minerals were observed
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