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Effect of pigskin-originated gelatin on dough properties and bread characteristics, especially on bread staling was investigated in terms of starch retrogradation and water migration in the present study. Results showed that gelatin significantly improved bread qualities during storage. Compared with the control, 7-day staling rate of bread containing 0.5% and 1.0% gelatin decreased by 6.56% and 20.83% respectively, indicating gelatin retarded the staling process of bread. This retardation effect was related to starch retrogradation and water migration. The relative crystallinity decreased from 15.12%, 11.60% to 10.75%, which demonstrated the alleviation effect of amylopectin crystallization. Bread samples containing 1.0% gelatin had the lowest retrogradation enthalpy of 2.93 ± 0.24 J/g followed by 0.5% gelatin bread and the control group, further indicating that gelatin may induce less water available to form crystal lattice and restrict the migration of starch molecules. The 5-day moisture loss rate for the control group was highest with the values of 12.39%, which was 1.43% and 1.83% higher than that of bread with 0.5% gelatin and 1.0% gelatin, respectively. Water activity and T 2 relaxation results provided the information that gelatin inhibited water migration upon storage and gelatin interacted with bread components. However, the effect of gelatin on improving bread quality and retarding staling could not be reflected by the dough properties measured through farinograph, extensograph and rheometer. This study suggested gelatin from pigskin had great potential to be served as an effective bread improver. Image 1 • Gelatin enhanced the bread qualities significantly, especially retarding the staling process. • Gelatin hindered the chain reassociation of starch molecules during storage. • Gelatin interacted with bread components and restricted water transfer. • Dough properties showed gelatin might to some extent weaken the gluten network. [ABSTRACT FROM AUTHOR]

Wheat flour superheated steam treatment can improve the baking food quality by modifying the functionality of wheat flour. To reveal the underlying mechanism of improving wheat flour quality by superheated steam treatment, the gluten molecular rearrangement and polymerization behavior of wheat flour upon superheated steam were studied. Molecular size distributions of samples were analyzed using size exclusion (SE-HPLC) and electrophoresis, which illustrated that superheated steam treatment promoted the aggregation of gluten due to cross-links of disulfide (SS) bonds. Superheated steam treatment increased the SDS-insoluble proteins content from 63.07% (native wheat flour) to 93.32% (treated at 150 °C for 1 min). Infrared spectroscopy (FTIR) was used to calculate the different secondary structures percentages of gluten, suggesting that superheated steam treatment increased intermolecular β-sheet and α-helix while it decreased anti-parallel β-sheet, β-turn and β-sheet. Furthermore, thermo gravimetric analysis (TGA) and rheology suggested that superheated steam treatment enhanced gluten mass but weakened gel system due to molecular rearrangements of SS bonds and hydrogen bonds. [Display omitted] • Gluten polymerization behavior of wheat flour upon superheated steam were studied. • Superheated steam treatment induced gluten aggregation and SS bonds cross-links. • Superheated steam treatment weakened the wheat flour gel system. [ABSTRACT FROM AUTHOR]

The structural and digestive properties of wheat flour which had been treated with superheated steam were investigated. Superheated steam treatment increased the degree of gelatinization (DG) and water absorption indexes (WAI) while decreased water solubility indexes (WSI) of wheat flour samples, compared with native wheat flour. The structural properties of wheat flour were characterized using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), particle size analyzer, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The starch granules agglomeration and denatured gluten proteins aggregation of samples were observed after treated with superheated steam. Additionally, Superheated steam treatment decreased the relative crystallinity and short-range order structure of starch. These structural changes were related to the starch digestibility. Superheated steam treatment caused the significant increase for slowly digestible starch (SDS) contents from 21.5% of native wheat flour to 35.0% of treated wheat flour (170 °C, 4 min). Additionally, the equilibrium hydrolysis concentration (C ∞) and the kinetic coefficient (k) of treated wheat flour were lower than native wheat flour, indicating that superheated steam treatment decelerated the hydrolysis rate. These results contributed to the applications of superheated steam technology in wheat flour modification. Image 1 • Structure and digestibility properties of wheat flour were studied. • Gluten aggregation of wheat flour was observed by superheated steam treatment. • Superheated steam treatment changed the structural characteristics of wheat flour. • Superheated steam treatment increased SDS and RS contents of wheat flour. [ABSTRACT FROM AUTHOR]