Ultrahigh magnetic field selectively promotes starch-fatty acid complexation depending on crystal type and fatty acid unsaturation.

Ultrahigh magnetic field (UMF) processing can modulate the properties of starch and alter starch crystallization. However, the effect of UMF in the formation of starch-fatty acid complexes remains limited, particularly regarding systematic comparisons across different crystalline starch and varied fatty acids. Using A-type wheat starch, B-type potato starch, saturated palmitic acid, and unsaturated palmitoleic acid as model systems, this study examined the effects of UMF treatment at two distinct stages (pretreatment and post-treatment) on starch-fatty acid complexation. UMF treatment at different stages significantly improved complexing ability and structural stability, as evidenced by increased complex index, relative crystallinity, and thermal parameters. Importantly, compared with post-treatment, UMF pretreatment is more effective, in which potato starch exhibits a stronger response than that of wheat starch. Specifically, the most prominent improvement was observed in the UMF-pretreated potato starch-palmitic acid complex, which achieved a CI of 62.69%, the relative crystallinity increased from 26.83% to 30.08%, and an enthalpy increase from 0.981 J/g to 1.295 J/g. Moreover, the saturated palmitic acid formed structurally more stable complexes than that of unsaturated palmitoleic acid. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses confirmed that UMF treatment preserved the V-type crystalline structure and promoted complexation. This study provides foundational data on the effects of UMF treatment at different stages on starch-fatty acid complexes, thereby laying a theoretical basis for the application of this technology in starchy food engineering.