Relationship between microstructure formation and in vitro starch digestibility in baked gluten-starch matrices.

Increased prevalence of diabetes prompts the development of foods with reduced starch digestibility. This study analyzed the impact of adding soluble dietary fiber (inulin-IN; polydextrose-PD) to baked gluten-starch matrices (7.5-13%) on microstructure formation and in vitro starch digestibility. IN and PD enhanced water-holding capacity, the hardness of baked matrices, and lowered water activity in the formulated matrices, potentially explaining the reduced starch gelatinization degree as IN or PD concentration increased. A maximum gelatinization decrease (26%) occurred in formulations with 13% IN. Micro-CT analysis showed a reduction in total and open porosity, which, along with the lower gelatinization degree, may account for the reduced in vitro starch digestibility. Samples with 13% IN exhibited a significantly lower rapidly available glucose fraction (8.56 g/100 g) and higher unavailable glucose fraction (87.76 g/100 g) compared to the control (34.85 g/100 g and 47.59 g/100 g, respectively). These findings suggest the potential for developing healthier, starch-rich baked foods with a reduced glycemic impact.

Effect of the Addition of Soluble Dietary Fiber and Green Tea Polyphenols on Acrylamide Formation and In Vitro Starch Digestibility in Baked Starchy Matrices.

Starch digestibility may be affected by food microstructural changes, as well as by specific interactions with some biomolecules, such as soluble dietary fibers (SDFs). It is well-known that acrylamide (AA) is a toxic and potentially carcinogenic compound formed in starchy food products processed at temperatures above 120 °C. This study aimed to investigate the effect of the addition of SDF and green tea polyphenols (GTP) on AA formation and in vitro starch digestibility in baked starchy matrices. The formulations were prepared using gluten and wheat starch, ensuring ~40 ± 2% (wet basis, w.b.) moisture in the doughs. In some samples, 7.5% (dry basis, d.b.) of starch was replaced with inulin (IN), polydextrose (PD) or partially hydrolyzed guar gum (PHGG), and/or with GTP at 1% (d.b). Acrylamide was determined by gas chromatography-mass spectrometry, and the in vitro starch digestibility using the Englyst method. The GTP was able to reduce AA content by ~48%, and a combination of IN-GTP allowed it to be reduced by up to ~64%, revealing the lowest rapidly available glucose content (~17 mg/g glucose). While a PD-GTP mixture reduced the AA content by around ~57% and gave the highest unavailable glucose fraction (~74 mg/g glucose) compared to the control. This study showed how functional ingredients could be used to develop successfully healthier starchy bakery foods.