A deep exploration of microstructural transformation and physicochemical property variation of corn starch under electron beam (EB) irradiation at 0–500 kGy and a use application of acrylic acid (AA) grafting

Abstract

EB irradiation is widely used for starch modification. Nevertheless, modification mechanism and level are blurry especially at a higher dose irradiation, restraining deep functional material design. In this work, pure corn starch was irradiated by an EB in air with dose up to 500 kGy. Then, microstructural and physicochemical property variations were explored via FT-IR, XPS, ¹³C-NMR, GPC, XRD, SEM, whiteness, TGA and viscosity analysis. Later, its post acceleration effect was explored via AA grafting. Main results reveal that irradiation induced severe starch backbone scission. Cleavage mainly occurred at α-1,4 glycosidic bond and the link of C-1 and C-2 atoms within starch glucose unit. Upon 500 kGy irradiation, number-average molecular mass-Mn-decreased from 2.56 × 10⁵ to 1.33 × 10³ Da, conversing macromolecule to small molecule debris. Certain hydroxyls were oxidized to carbonyls. Molecule chain stacking regularity was destroyed. Amorphization occurred shown a crystallinity reduction close to 34%. Synchronously, color be darken, cracks and micropores were generated, thermal-stability and viscosity decreased. In details, whiteness and viscosity decreased from 91.3 ± 0.1 and 1539 ± 5 to 45.3 ± 1.6 and 0 mPas and the fastest speed thermal-decomposition temperature decreased by 6 °C. It seems a dose of 500 kGy EB irradiation deteriorated starch microstructure and physicochemical property sufficiently. However, it promotes post AA grafting efficiently. Via a dose of 100 kGy EB irradiation and certain level AA grafting a QH₂O as 687.9 ± 19.5 sample was achieved, showing a 1.16 times elevation compared to sample without pre-irradiation, implying sufficient acceleration effect. These findings promote EB irradiation technology use in starch-based functional material design and starch irradiation damage mechanism, sustaining visible use and academic values. In addition, the prepared grafted product possibly sustains a use application in agriculture field, sustaining potential commercial profit, attractive.