engleski

Iron availability of different types of inulin enriched integral biscuits: Studies using an in vitro digestion/Caco-2 cell culture model

Iron deficiency is the most prevalent nutrient deficiency among humans, mostly due to the low bioavailability of dietary iron, especially in widely consumed plant-based foods such as wheat, rice, maize etc. Therefore ways need to be found to increase the density and bioaccessibility of iron in these types of foodstuff. In the frameworks of our research wheat flour based biscuit composition was modified by addition of mixture of inulin with one of the following raw materials: soy flour, amaranth, carob, oat fiber and apple fiber. Modifications were conducted with the aim of generally improving its nutritive value and functionality while the special emphasis has been laid on increasing the total content, solubility and absorption of iron from the final product. Iron content was assessed using ICP-AES in samples previously wet ashed using microwave digestion procedure. Bioaccessible iron was determined in soluble sample fractions after in vitro simulation of gastrointestinal digestion. Iron uptake was determined using Caco-2 cell model (as the sum of iron absorbed, and transported across the monolayer). Caco-2 cells have been proven very applicable for assessing mineral utilization from different foodstuff since results obtained on Caco-2 monolayer correlate very well with human studies data. Obtained results reveal that total iron content ranged from 2.2 (referent sample) up to 3.7 mg/100g dry matter (sample with oat fiber). Significant increase of iron content was also achieved using soy flour and amaranth for enrichment. The content of bioaccessible iron was significantly lower, ranging from 0.65 (samples with addition of apple fiber and carob), up to 1.75 mg/100g dry matter (sample with soy flour). Total iron uptake on Caco-2 cell monolayer was low, ranging from 7-14 % of bioaccessible fraction. The highest uptake was from biscuits enriched with amaranth and soy flour (0.11 and 0.09 µ ; g/well, respectively). The amounts of bioavailable iron and iron absorbed on cell monolayer did not correlate significantly, indicating the existence of other factors also involved in iron absorption (linkage and/or valence of iron ; presence of other divalent metals competing for metal transporter etc.). Although all modifications of referent biscuit composition resulted in significant increase of iron content, improved bioaccessibility and uptake of iron was only achieved by using soy flour and amaranth. Obtained results therefore emphasize that, in addition to its total content, iron bioavailability and uptake should also be determined when evaluating certain foodstuff as the nutritive source of this essential trace element.

Iron; biscuits; Caco-2

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