Effects of Ultra-High Pressure–Cellulase Pretreatment on the Structural Characteristics and Functional Properties of Soluble Dietary Fiber from Perilla Seed Hulls and Its Application in Wheat–Corn Composite Dough

Abstract

Perilla seed hulls are a promising but underutilized source of dietary fiber, yet little is known about how pretreatment-induced structural changes in soluble dietary fiber (SDF) derived from these hulls affect its functionality in cereal dough. This study compared SDF extracted from untreated, ultra-high-pressure (UHP)-pretreated, cellulase-pretreated, and sequentially UHP–cellulase-pretreated perilla seed hulls and evaluated their structural, physicochemical, and dough-modifying properties. The combined treatment increased the SDF content of the hull material from 3.71% to 8.63% and decreased insoluble dietary fiber from 55.74% to 50.37%. Relative to untreated SDF, the resulting UCPSDF had a lower apparent molecular weight (2442 vs. 2788 Da), a smaller mean particle size (2.76 vs. 3.62 μm), a lower glucose proportion, and higher arabinose and acidic monosaccharide proportions. FTIR, XRD, SEM, and thermal analyses indicated retention of the principal polysaccharide and cellulose-I signatures, accompanied by changes in structural characteristics and a looser, more porous morphology. UCPSDF also showed the highest water-holding and swelling capacities. At 6% supplementation, UCPSDF produced the strongest elastic response in wheat–corn composite dough, significantly increased springiness (0.59–0.72) and cohesiveness (0.64–0.76), increased the combined amide I-derived α-helix and β-sheet proportion of dough proteins from 53.93% to 66.82%, and reduced the T23 relaxation time from 297.86 to 81.23 ms. These findings indicate that sequential UHP–cellulase pretreatment improves the measured SDF content and hydration functionality of perilla seed hull SDF and supports its use as a dough-structuring ingredient in wheat–corn composite foods.