Modulation of structural transitions, integrity, and digestibility in deep-defatted pea starch noodles through supplementation with partial defatting of common vetch starch

Abstract

Defatting is an effective strategy for modifying the structural and functional attributes of pea starch; however, extensive surface granule defatting markedly compromises viscosity, thermal, and gel stability. This study investigated the combined effects of deep-defatted pea starch (DDPS) and partially defatted common vetch starch (PDCVS) on the structural integrity and digestibility of gluten-free noodles. Pea and vetch starches were defatted for 18 h and 12 h, respectively, to produce DDPS and PDCVS. Deep defatting disrupted crystalline lamellae, reduced gelatinization enthalpy, and weakened gel strength due to the loss of amylose-lipid complexes. Incorporation of PDCVS (10-40%) counteracted these effects in a concentration-dependent manner. Moderate substitution (10-20%) promoted partial recrystallization (relative crystallinity = 17.53-16.69%), increased gelatinization enthalpy (∼2.24 J/g), and enhanced viscoelastic moduli, indicating restoration of ordered double helices. The transformation of the crystalline pattern from C- to C_a-type and increased short-range molecular order (1047/1022 cm^-1 = 1.057-1.069), accompanied by the formation of amylose-lipid complexes (single helix: 5.63-6.50%), confirmed that 10-20% PDCVS enhanced helical stability and molecular order while mitigating electrostatic repulsion. Microstructural observations and spatial lipid distribution revealed compact, homogeneous matrices with uniformly distributed lipid-amylose domains, whereas ≥30% PDCVS induced porous heterogeneity. During refrigerated storage, 10-20% PDCVS noodles maintained superior texture, higher water retention, and delayed retrogradation. Digestibility assays showed restricted enzymatic access, yielding the lowest equilibrium hydrolysis (C_∞ = 84.32%), estimated glycemic index (eGI = 65.91), and resistant starch content of 15.71%. Overall, moderate PDCVS supplementation effectively compensates for deep-defatting-induced fragility, enhancing structural resilience and digestive resistance, and demonstrates a novel dual-defatting approach for developing functional, low-glycemic legume starch noodles.

Keywords: Digestibility control; Dual-defatting; Gluten-free noodles; Legume starch; Molecular ordering; Retrogradation behavior.