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

Total calcium content, calcium solubility and calcium uptake and retention on Caco-2-cell monolayer were determined with the aim of evaluating different types of whole grain biscuits as additional sources of calcium in everyday nutrition. Referent wheat flour based biscuit composition (based on wheat flour types 500 and 1700) was modified by addition of mixture of inulin with one of the following raw materials: soy flour, amaranth, carob, oat fiber and apple fiber. Although the modifications were conducted with the aim of generally improving its nutritive value and functionality, the special emphasis has been laid on increasing the total content, solubility and absorption of calcium from the final product. Calcium content was assessed using ICP-AES in samples previously wet ashed using microwave digestion procedure. Bioaccessible calcium was determined in soluble sample fractions after in vitro simulation of gastrointestinal digestion. Calcium uptake was determined using Caco-2 cell model (as the sum of calcium 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 calcium content ranged from 60.91 (referent sample) up to 107.8 mg/100g dry matter (sample with carob). Significant increase of calcium content was also achieved using soy flour and amaranth for enrichment. The content of bioaccessible calcium was significantly lower, ranging from 25.91 (sample with addition of apple fiber) up to 35.97 mg/100g dry matter (sample with carob). Total calcium uptake on Caco-2 cell monolayer ranged from 26.39 to 38.95 % of bioaccessible fraction. The highest uptake was from biscuit enriched with amaranth (5.45 µ ; ; g/well). Although all modifications of referent biscuit composition resulted in significant increase of calcium content, improved bioaccessibility (and uptake) of calcium was achieved only by using soy flour, carob (and amaranth). Obtained results therefore emphasize that, in addition to its total content, calcium bioavailability and uptake should also be determined when evaluating certain foodstuff as the nutritive source of this essential trace element.

biscuits; Caco-2 cells; calcium availability; ICP AES

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