ABSTRACTThe binding of endogenous copper, zinc and iron in six fiber sources was examined via incubation under three pH conditions: (1) pH 0.65; (2) pH 6.8; and (3) a sequential treatment of pH 0.65, neutralization, then pH 6.8. After both the pH 6.8 and sequential treatments, most of the minerals remained bound in the residues, while little remained bound after the acidic treatment. This indicated that the minerals were rebound when the pH was raised from very acidic to only slightly acidic. Titrations of the untreated fiber sources showed that protein influenced the hydrogen ion buffering capacity. After enzymatic proteolysis, the buffering capacities were reduced and other physicochemical properties appeared to gain influence.
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