Effect of Degree of Polymerization of Amylose on in Vitro First-Order Digestion Kinetics of Ternary Complexes of Seedless Breadfruit Starch, Lauric Acid and β-Lactoglobulin

Objective: This study aimed to investigate the influence of degree of polymerization of amylose on the digestibility characteristics of its ternary complexes. Methods: Ternary complexes of seedless breadfruit starch, prepared by separately mixing amyloses extracted from five cultivars (GJS, FSS, SMS, SS and CS) with amylopectin extracted from GJS, having the highest degree of polymerization among amylopectins from these cultviars, at a 1:1 ratio were prepared with lauric acid (LA) and β-lactoglobulin (β-LG) and characterized for supramolecular structure and digestion kinetics by high-performance size-exclusion chromatography (HPSEC), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. All five complex samples displayed obvious characteristic peaks of ternary complexes, V-type crystalline structure and rodlike molecular configuration. As the degree of polymerization of amylose increased, the complexing index (CI) (from 68.81% to 83.55%), relative crystallinity (from 21.10% to 28.35%), short-range order (from 0.44 to 0.63), molecular mass (from 2.90 × 106 to 8.02 × 106 Da), molecular density index (from 3.50 to 23.07 g/(mol·nm3), gelation temperature (from 98.52 to 103.71 ℃), and gelation enthalpy (from 13.95 to 18.73 J/g), second-order kinetic rate constant (from 1.00 × 10-2 to 2.92 × 10-2 min-1) increased, while the semicrystalline lamellae thickness (from 3.20 to 4.82 nm), mass fractal dimension (from 1.28 to 1.81), characteristic length of crystallite unit (from 6.33 to 7.01 Å), radius of gyration (from 70.31 to 93.94 nm), and nanosurface “blocklet” size (from 7.05 to 15.03 nm) dropped, which led to a decrease of in vitro glycemic index (from 78.83 to 85.71). Statistical analysis showed that the degree of polymerization of amylose could remarkably affect the multiscale superstructure of the ternary complexes, which in turn could change its digestion kinetics. The results provide new theoretical guidance for the production of starch-based multicomponent foods. © 2023 Chinese Chamber of Commerce. All rights reserved.