Phytic Acid as a Phosphorus Reservoir in the Developing Potato Tuber

Abstract

PHYTIC acid is present in the mature potato tuber, as a mixture of dicalcium monomagnesium salts of inositol hexa- and penta-phosphoric acids^1,2. The present communication provides information on the effect of maturity and post-harvest storage temperature on the phytic acid content of the potato tuber. Table 1 shows that the phytic acid phosphorus content of freshly harvested tubers increases with increasing maturity, but does not change greatly on subsequent storage at either 25° or 0°. Table 1 also shows that the percentage of total phosphorus present as phytic acid increases with increasing maturity, especially during later stages of development. Thus two-thirds of the increase in phosphorus content per 100 gm. of tuber observed between 80 and 102 days after planting appears as phytic acid phosphorus, whereas at earlier stages of development the incoming phosphorus is preferentially incorporated into starch³. Between two-thirds and four-fifths of the total organically bound acid-soluble phosphorus is present in the tuber as phytic acid phosphorus³. Although the phytic acid contributes a substantial portion of the total phosphorus of the tuber, its concentration in tubers amounts to less than 0.1 per cent of the fresh weight of the tuber.