Liquid nitrogen ball-milled mechanochemistry prior to dry heating regulates the multiscale structure and...

Liquid nitrogen ball-milled mechanochemistry (BM), with favorable clean-label characteristics, is a novel method used industrially for starch processing. In this study, corn starch (CS) was subjected to BM for 20 min, followed by dry heating (DH) treatment at 130 °C for 2-4 h. Microstructural observations revealed that DH-treated starches maintained an integrated granular structure with slight aggregation. BM-treated starch displayed a collapsed granular structure, while starches subjected to combined BM and DH modifications exhibited a morphology similar to that of BM-treated starch. The modifications altered the starch molecular structure, as demonstrated by the observed changes in amylose content (increasing from 26.14% to 27.72%-30.45%), molecular weight (decreasing from 69,385.75 kDa to 57,000.91-68,642.37 kDa), and the average degree of polymerization (DP) of amylopectin (decreasing from 21.63 to 20.72-21.61). The results of X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy revealed damaged crystalline structure and reduced short-range ordered structure in modified starches, as evidenced by the reduction in relative crystallinity (RC) from 28.76% to 12.68%-26.94%, the decline in the R_1047/1022 from 0.943 to 0.741-0.902, and the increase in FWHM₄₈₀ from 23.30 to 24.65-27.51. The modifications also facilitated the starch gelatinization and thermal degradation, while significantly altering the swelling power, solubility, and in vitro digestibility of starches. These findings demonstrated the potential of combined BM and DH modifications as an innovative approach for modulating the multiscale structure and physicochemical properties of starch, broadening its functional utility in food-related applications.