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The effect of pH ar!d heat treatment on the binding of added food grade sources of calcium, magnesium, zinc, and iron to a standard wheat bran, cellulose, and lignin was investigated. 1% solutions of pectin and guar gum were examined for their ability to bind these metals in aqueous rolution. Lignin and pectin was found to have high metal binding capacities. Metal binding to fiber was found to be pH dependent. Toasting had no effect on metal binding by cellulose, but had a sign ficant effect on the binding of metals by lignin and wheat bran. BrGling had a significant effect on the binding of metals by cellulose, lignin, and wheat bran. INTRODUCTIONTHE ROLE OF FIBER in the diet was at one time considered to be of little consequence to health, if not actually undesirable in a food product. Once believed to be an inert substance, dietar), fiber has now been found to be a complex chemical entity capable of reaction and interaction within a food matrix and within the human digestive system.Recently, Rubio and Falkenhag (1979) have shown dietary fiber compor!ents to be effective in complexing such carcinogenic comlrounds as nitrosamines.However, a major negative effect to increased consumption of dietary f.ber may be a reduction in the bioavailability of trace ninerals to the body from the gastrointestinal tract. One ccmponent of dietary fiber, pectin, has long been known to form chelates with a number of divalent metals. Schweiger (1966) has given data in support of the formation of bot 1 intermolecular and intramolecular chelates of pectin with divalent metals. Whether this complexation is strong enough to significantly impair mineral bioavailability remairts to be seen. Furda (1979) has reviewed the interaction cf pectinaceous dietary fiber with some metals and lipids. The authors results indicate that calcium ions are bound t 3 pectin molecules primarily by electrostatic attractive forces.Thompson ant1 Weber (1979) studied the binding of copper, zinc and iron to various fiber sources including wheat bran, corn bran, soy bran, oat hulls, rice bran and cellulose under conditions which parallel the physiological pH of the stomac:h and duodenum. These workers found that while the entlogenous minerals were not bound to the fibers at the very acidic pH, they were rebound when the pH was raised. Reinhold et al. (1976) reported a negative balance of calcium, magnesium, zinc and phosphorus in a two-man experiment during a 20-day period of high fiber consumption. The authors concluded that metals bound by dietary fiber remain unavailablt for absorption. Although the fibers may be attacked by tie microflora of the large intestine with release of the mt:tals, absorption can no longer occur in this region and th: metals are therefore unavailable for ab-

A quantitative HPLC method for the analysis of phytic acid in foods was developed based on the precipitation of phytic acid with ferric chloride followed by conversion to sodium phytate before injection onto a Cl8 reversed-phase column. Standard food grade wheat bran samples were analyzed by the method of standard addition and recovery of phytic acid ranged from 99-103%. 3% H2SO4 was found to be as effective as 3% TCA in the extraction of phytic acid. AAS was shown to be potentially valuable as a metal specific detector for the HPLC of phytate-metal complexes.

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.

The four major anthocyanins of cranberries were separated and purified by conventional paper chromatography. The purified individual anthocyanins were eluted from the paper by methanol-acetic acidwater (90:5:5) and concentrated on a rotary evaporator (<30"(Z). The individual anthocyanins were chromatographed separately and in a mixture by a reversed-phase high-pressure liquid chromategraphic (HPLC) system. Complete separation of all four anthocyanins took less than 1 hr 40 min. A SO-ml sample of commercial Cranberry Juice Cocktail first purified by a GC-50 ion exchange column before injection into the HPLC showed the presence of two additional pigments when chromatographed.