In vitroavailability of zinc from infant foods with increasing phytic acid contents

Abstract

An in vitro method was used to determine the availability of Zn from infant foods containing increasing amounts of phytate, and to quantify the effect of the phytate:Zn molar ratio on the availability. During the in vitro assay, digestive conditions of infants, younger and older than 4 months of age, were carefully simulated since the solubility of phytate -Zn complexes during digestion is pH dependent. Availability was measured with a continuous flow dialysis in vitro procedure with previous intralumen digestive stage. Zn concentrations were determined with flame atomic absorption spectrometry. Phytic acid content was measured with HPLC. Adding phytate to infant formula lowered Zn availability to 2 : 84 (SD 0 : 17) % when the phytate:Zn molar ratio increased to 2 : 2 ðP , 0 : 05Þ; as compared with cows' milk-based formula (6 : 65 (SD 0 : 55) %). Availability from vegetables (23 : 83 (SD 2 : 17) %) significantly decreased ðP , 0 : 05Þ at a ratio . 7 : 9 (15 : 12 (SD 1 : 63) %). Zn availability from soyabean-based formula (2 : 26 (SD 0 : 36) %) was lower ðP , 0 : 05Þ compared with cows' milk-based formula (6 : 65 (SD 0 : 55) %). Availability between soyabean-and cows' milk-based formula was similar ðP . 0 : 05Þ when a phytate:Zn ratio of 2 : 2 (2 : 84 (SD 0 : 17) %) was obtained in the cows' milk formula. The negative effect of phytic acid on Zn availability was dependent on the type of the food and the phytate content, and should be considered when using soyabean-based formulas during early infancy.

Rapid Measurement of Phytate in Raw Soymilk by Mid-infrared Spectroscopy

“…Phytate is also known as an antinutrient that inhibits the intake of polycationic minerals such as calcium, zinc and iron. [7][8][9] Hence, many methods for its measurement and elimination have been investigated. Some methods for measurement using ferric precipitation, [10][11][12] HPLC, 13,14) or other methos 15,16) are established, but these are too time-consuming to use in the tofu-making process.…”

Effect of pea and soya bean interaction on zinc dialyzability in weaning foods

“…10 Apart from these indirect factors involving the relationship between phytic acid, Zn and Ca, other direct factors such as pH are reported to play a critical role in determining zinc solubility 11,12 and dialyzability. 13 An earlier paper 2 showed the effect of pea, soya bean, ascorbic acid and ferrous sulphate on the dialyzability of Cu, Zn and Fe in veal + vegetable weaning foods; a secondary effect implying the antagonistic interaction of pea and soya bean was also obtained but not discussed at that time. A better understanding of the reason for this antagonistic effect might increase our knowledge of the mechanisms governing Zn dialyzability; while in vitro studies show complete agreement regarding the phytic acid-Zn relationship, in vivo research into the effect of phytic acid on Zn bioavailability has yielded conflicting results, because the amount of mineral available for absorption is dependent upon dietary composition, gastrointestinal secretions and luminal interaction.…”

Atomic spectrometry update. Clinical and biological materials, foods and beverages

“…Samples were simply subjected to a dialysis procedure prior to analysis by FAAS. 232 Other papers report extraction of As, Cu, Fe and Hg from samples using various acids and/or solvents at different heating conditions (see Table 1). …”

“…305 The influence of phytate in infant foods on Zn bioavailability was studied in vitro. 232 The concentrations of 18 elements in three different infant formulas were compared and while most were equivalent in all three, there were some exceptions noted. 306 There is considerable current interest in infant exposure to Hg during pregnancy and from human milk, where the maternal dietary intakes are high.…”

“…232 A methane-air flame was investigated for the measurement of Rb in water by FAES. Flame composition, observation height and spectral bandpass were optimized and an LOD of 2.3 mg l 21 was obtained.…”