The effect of hydrodynamic conditions on the monogastric-like in vitro digestion of maize flours dried at different temperatures

Abstract The effect of hydrodynamic conditions on the in vitro digestion of two maize varieties (flint-dent and flint maize), dried at different temperatures (54 °C, 90 °C or 130 °C), was assessed. During the digestion assay, maize flours were mixed using either gentle agitation (a shaking bath) or rotational agitation at four different speeds. Increasing rotational agitation gradually increased the digestibility of the in vitro dry matter (IVDMD) and of starch (IVSD) by 15 and 20%, respectively, and also affected the rate of starch amylolysis. The increase in digestion with the mixing rate was modulated by the thermal history suffered by the feedstuff materials. The variability introduced by flour thermal histories makes it difficult to compare the digestibility of such materials of unknown origin without the standardization of mixing procedures. Flour thermal history also results in different rheological properties of samples, with potential implications for enzymatic digestion that current static in vitro protocols are not able to reproduce. In order to improve the predictive quality of static in vitro models and for a reliable comparison of the digestibility of foods and feedstuffs, hydrodynamic and mixing procedures need to be optimized and standardized.