Effect of pH and Heat on the Binding of Iron, Calcium, Magnesium, and Zinc and the Loss of Phytic Acid in Soy Flour

Abstract

The effect of pH and heat treatments on the binding of iron, calcium, magnesium and zinc and the loss of phytic acid in defatted soy flour was investigated. The soy flour was found to bind more iron, calcium, and magnesium at pH 6.8 than at pH 5.0, but the reverse situation occurred with zinc. Boiling caused a significant increase in binding of zinc and magnesium at both pH values, but was pH dependent for iron and calcium. Toasting caused a significant increase in binding of zinc and calcium at both pH values and a pH variable effect on iron and magnesium. Phytic acid analysis under the same conditions suggested that the degree of binding of these minerals did not correlate with the presence of phytic acid.

Effect of Iron Sources and Ascorbic Acid on the Chemical Profile of Iron in a Soy Protein Isolate

“…That is, at pH 4.5 there is an isoelectric problem which may not exist at pH 5.0 or above. For instance, Clydesdale and Camire (1983) found an increase in total soluble iron when defatted soy flour was incubated at pH 5 .O rather than 6.8. However, it should be remembered that soy flour contains about 50% carbohydrate, much of it in the form of fiber,which has been shown repeatedly to release minerals in a soluble form as the pH is lowered (Camire and Clydesdale, 1981;Reinhold et al, 1981).…”

The chemical composition and membrane stability activity of some herbs used in local therapy for anemia

“…Theobroma cacao root recorded the least soluble and available iron despite its high total iron content probably due to the high level of fibre, most especially cellulose, which has been reported to bind minerals (Reinhold et al, 1982). The high pH of its decoction (pH 6.5) could also contribute to the low solubility of its iron as indicated earlier (Clydesdale and Camire, 1983). The result also showed that iron was more soluble and available from the stalk of red Sorghum bicolor compared to the white cultivar possibly reflecting the difference in their pH (6.7 and 5.5 for white and red cultivars, respectively) and tannin (0.20 and 0.03 mg/dm 3 for white and red cultivars, respectively).…”

“…The highest calcium solubility and availability was recorded for Sobo as reported earlier for iron and possibly for the same reasons (Adewusi et al, 1999). Other decoctions recorded less than 5% available calcium, which may be a consequence of their tannin and fibre content and more importantly the high pH of the decoctions in which calcium is expected to precipitate (Clydesdale and Camire, 1983). As observed in iron, colored compounds (Table 4) did not seem to have any significant effect on the availability of calcium.…”

Dialyzable Calcium from Milk Processed with Soluble Fiber‐Containing Gums, Thickeners, and Cocoa

“…The ability of dietary fiber to bind cations is one of the most important causes of reduced bioavailability of such minerals as calcium, zinc and iron from the gastrointestinal tract (Reinhold et al, 1976;Camire and Clydesdale, 1981;Rendleman, 1982;Clydesdale and Camire, 1983;Clydesdale, 1985, 1986). Though most of these studies have focused on the effects of insoluble dietary fibers, a few of them have included soluble fiber sources to observe their effects on mineral availability.…”