EFFECT OF COEXISTING ESSENTIAL HEAVY-META LS ON THE ESTIMATION OF LEAD IN NATURAL FOOD-ADDITIVES BY HEAVY-METALS LIMIT TEST

The concentrations of heavy metals in commercial natural food additive s (9 items, 10 products) used to increase the shelf life of foods were determined. Pb content was below 3 mu g/g in all items, though some i tems contained about 10 mu g/g of Cu or over 200 mu g/g of Fe. The inf luence of Cu and Fe on the Heavy Metals Limit Test was investigated us ing the items that contained large amounts of Cu or Fe. Although not d arker than the color of the control solution (the limit was set at 20 mu g/g as Pb), darkening was observed in the test solution of the pepp er extract that showed the highest concentrations of Pb and Cu. Since the color of 100 mu g/g of Cu corresponded to that of 40 mu g/g of Pb, Cu in the pepper extract contributed more to the darkness than the Pb . In an HPLC-ICP study on a neutral solution of pectin digests, an Fe peak, which may be ascribed to Fe bound to galacturonic acid, was obse rved. Since various metals are present in commercial products of natur al food additives, it is considered that specifications for, at least, lead, heavy metals, and arsenic should be established for natural foo d additives.