Binding of mineral elements to locust bean gum influences availability in vitro

Experiments were conducted to evaluate the extent to which element binding of locust bean gum (LBG) affects the availability of calcium, iron, and zin c in the gut. Infant formula was supplemented with increasing amounts of LB G and subjected to an intraluminal digestion procedure. Element binding was measured by eliminating the complexes by twofold centrifugation. Availabil ity of the elements was determined using a validated continuous-flow dialys is technique. Elemental content of the samples, supernatants, and dialysate s was analyzed with validated atomic absorption spectrometry. LBG provided small amounts of intrinsic calcium (1.13 +/- 0.02 mg/g) and trace amounts o f iron (0.02 +/- 0.00 mg/g) and zinc (0.01 +/- 0.00 mg/g), which were stron gly bound to the LBG molecule (respectively: 76.6 +/- 3.3%, 83.4 +/- 1.2%, 96.7 +/- 6.6%). Correlation analysis, between percent element bound by LBG after centrifugation and percent trapped after dialysis, yielded significan t correlation only for the data of zinc (r = 0.93). For calcium and iron, n o correlation could be demonstrated, however, for iron a similar trend was observed. These findings suggest that element binding of LBG has a major in fluence on the availability of zinc and maybe of iron. For calcium, other f actors might also be involved, affecting availability.