The retrogradation of 5, 10, 15, and 25% corn starch gels was measured using differential scanning calorimetry (DSC), rheology, and an array of NMR spectroscopy techniques. During the initial (<24 h) stage of retrogradation, an increase in G' corresponding to an increase in the number of solid protons participating in cross-relaxation (M(B)(0) was observed for all four concentrations studied. During the latter (>24 h) stage of retrogradation, amylopectin recrystallization becomes the dominant process as measured by an increase in deltaH(r) for the 25% starch gel, which corresponded to a further increase in. A decrease in the molecular mobility of the liquid component was observed by decreases in (17)O T(2), (1)H D(0), and T(2A). The value for T(2B) (the solid transverse relaxation time) did not change with concentration or time indicating that the mobility of the solid component does not change over time despite the conversion of the highly mobile starch fraction to the less mobile solid state during retrogradation.

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Addition of fiber to foods represents a strategy for increasing nutritional quality and health benefits but food matrix and processing play an important role in the properties of the final product. We investigated the effect of different conditions of extrusion on the digestibility of corn‐based cereal puffs with and without 15% fiber added. Two wheat fractions (bran or aleurone) were used as dietary fiber sources. Our results indicate that in vitro carbohydrate digestion of extruded products was faster and more extended than the non processed mixes, regardless of the formulation (presence or absence of fiber) or the conditions of extrusion. We also evaluated the presence of steryl ferulates (campestanyl ferulate, sitostanyl ferulate, and campesteryl ferulate) after in vitro digestion of the aleurone containing materials and observed increased amounts in solutions from extruded cereals compared to non processed raw mixture; this suggesting that processing by extrusion may increase bioaccessibility of health related compounds present in aleurone. Studies on the kinetics of steryl ferulates release and hydrolysis during in vitro digestion are ongoing. Funded by Cargill Inc

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