Abstract: In order to study the impact of heat moisture treatment (HMT) on the aggregation structure and pasting behavior of adlay starch, starch extracted from adlay seeds was adjusted to moderate moisture content (20%, 25% and 30%) and then subjected to HMT at 110 ℃ for 4 h. The effects of HMT on the granular structure, crystalline structure, short-range ordered structure and molecular ordered structure were investigated by scanning electron microscope (SEM), X-ray diffraction, Fourier transform infrared spectrometer (FTIR), Raman spectrometer and differential scanning calorimeter (DSC). Furthermore, the pasting parameters of HMT treated starch including pasting temperature, peak viscosity, breakdown and setback values were recorded, and the relationship between their aggregation structure and pasting behavior was constructed. It was revealed that during HMT thermal energy and water molecules could synergistically induce damage to the aggregation structure of adlay starch, causing pits and pores on the surface of starch granules or even their rupture, reduce relative crystallinity, decrease the ordered degree of short-range ordered molecular structure and unravel double helices, thus resulting in a reduction in swelling power and peak viscosity. Meanwhile, HMT could enhance the interaction between starch chains and lead to rearrangement and reorientation of the molecular ordered structure, improved double-helical structure and microcrystaline structure and starch granule aggregation. All these structural changes promoted an increase in onset pasting temperature and a decrease in breakdown and setback values. These results indicated that adlay starch treated with HMT possessed lower viscosity and higher stability to both low and high temperatures, thereby showing excellent application potentials for the food industry.

Key words: adlay starch; heat moisture treatment; aggregation structure; pasting behavior