IN-VITRO BINDING-CAPACITY OF VARIOUS FIBER SOURCES FOR MAGNESIUM, ZINC, AND COPPER

Sixteen fiber sources provided by different commercial suppliers were analyzed for moisture, acid detergent fiber (ADF), lignin, and endogen ous minerals. They were further acid washed to strip them of their end ogenous minerals and tested for their total binding capacity for magne sium (Mg), zinc (Zn), and copper (Cu). ADF content ranged from 14.5% f or rice bran to 65.5% for pea fiber and lignin content from 0.5% for s oy bran to 66% for pea fiber. Endogenous Mg varied from 250 mu ug/g fo r corn bran to 7995 mu g/g for wheat bran. Zn levels were from 1.1 mu g/g (oat ''bleached'' fiber) to 156 mu g/g (wheat bran); those of Cu r anged from 1.0 mu g/g (apple fiber) to 67.6 mu g/g (peanut fiber). Aci d washing was efficient in removing most endogenous minerals from fibe r sources. The amounts of minerals bound varied significantly (P < 0.0 5) among fiber sources. Levels of Mg bound to acid-washed fibers range d from 525 mu g/g (oat hulls) to 4420 mu g/g (pea fiber Centara), whil e those of Zn and Cu varied from 1861 mu g/g (oat hulls) to 6990 mu g/ g (wheat bran) and from 639 mu g/g (corn bran) to 7976 mu g/g (barley fiber), respectively. Correlations and intercorrelations between the a mount of minerals bound and protein, ADF, and Lignin contents of acid- washed fiber sources were low because of the variation in the chemical composition and chemical structure of the fiber sources.