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 endogenous minerals. They were further acid washed to strip them of their endogenous minerals and tested for their total binding capacity for magnesium (Mg), zinc (Zn), and copper (Cu). ADF content ranged from 14.5% for rice bran to 65.5% for pea fiber and lignin content from 0.5% for soy bran to 66% for pea fiber. Endogenous Mg varied from 250 micrograms/g for corn bran to 7995 micrograms/g for wheat bran. Zn levels were from 1.1 micrograms/g (oat 'bleached" fiber) to 156 micrograms/g (wheat bran); those of Cu ranged from 1.0 micrograms/g (apple fiber) to 67.6 micrograms/g (peanut fiber). Acid washing was efficient in removing most endogenous minerals from fiber sources. The amounts of minerals bound varied significantly (P 0.05) among fiber sources. Levels of Mg bound to acid-washed fibers ranged from 525 micrograms/g (oat hulls) to 4420 micrograms/g (pea fiber Centara), while those of Zn and Cu varied from 1861 micrograms/g (oat hulls) to 6990 micrograms/g (wheat bran) and from 639 micrograms/g (corn bran) to 7976 micrograms/g (barley fiber), respectively. Correlations and intercorrelations between the amount 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