The application of an in vitro method for mineral bioaccessibility estimation in the nutritional optimization of special food formulas

Abstract

Enteral formulas (EF) are complex food systems having all the necessary nutrients for complete human nourishment. However, there are components in EF that can interact with minerals, reducing their absorption and therefore EF nutritional quality. Dialyzability is an in vitro technique that can be used as an estimator of bioaccessibility of a particular mineral. It is the ratio of an element that diffuses through a semipermeable membrane during simulated gastrointestinal digestion after a period to allow equilibrium. In order to optimize mineral bio-accessibility of enteral formulas, the effects of soy protein (SP) and casein protein (CP) ratios (0, 50, and 100%), and polydextrose content (Px: 8.0, 16.5, and 25.0 g L-1) on Fe, Zn, and Ca bioaccessibility (%DFe, %DZn, and %DCa) were studied using the dialyzability method. Also, protein digestibility (%PD) was assayed. Experimental normal-protein (40 g L-1 protein) EF was developed and evaluated using a response surface design. Two control samples without Px and with only SP or CP were carried out. As an estimator of bioaccessibility for a particular mineral, the in vitro mineral dialyzability assay was used. Results appeared as SP content increased, %DFe (10.56-14.62%), %DZn (3.17?8.19%) and %PD (85.97?100%) decreased, probably due to the increased levels of phytic acid and trypsin inhibitors from SP isolate. %DCa (22.33 ± 22.99%) was not affected by any analyzed factors. Px did not affect any response variable in the design. However, it impaired mineral bioaccessibility of SP-EF compared with the same formulation without Px, although this effect was not observed for CP-EF, suggesting physicochemical interactions among nutrients affecting solubility were present in SP-Px-EF. The responses for an optimized enteral formula were: %DFe: 14.5; %DZn: 8.1; %DCa: 22.8 and %DP: 100.0. The use of the dialyzability assay as an indicator of mineral bioaccessibility contributes to defining special food formulas in such a way that they provide adequate bioavailable mineral quantity to achieve nutritional targets.