No abstract

It is generally believed that acetylation can enhance the hydrophilicity of starch, resulting in increased viscosity. However, moderate vinyl acetate acetylation is interestingly found to decrease the peak viscosity of oxidized starch during pasting in this study. This low viscosity of starch paste is extremely desirable in paper surface sizing and textile sizing. Corn starches are oxidized by NaClO (4.0% chlorine) and then acetylated using vinyl acetate at different levels. The peak viscosity of oxidized starch modified by vinyl acetate is reduced by 67.1%. Fourier transform infrared spectroscopy confirms the presence of acetyl groups with a peak at 1730 cm−1. X‐ray diffraction analysis shows that the intensity of crystalline peaks of oxidized–acetylated starches is decreased compared with that of oxidized or acetylated starch. Granule morphology observations further reveal extensive surface damage of the granules resulting from moderate acetylation. Molecular size distribution analysis also shows that the moderate vinyl acetylation can significantly reduce (≈60%) the average molecular weight of oxidized starch. These results show that moderate acetylation can change the structural and morphological properties of oxidized starch, leading to a considerable drop in paste viscosity and shows great application potential in the starch industry.

Thermal stabilization is efficient for slowing lipid degradation and prolonging the shelf life of highland barley, but the impacts of different thermal stabilized treatments on highland barley and possible chemical reactions remain unclear. The effects of thermal stabilization treatments (bake, far-infrared, fry, microwave and steam) on the enzymes, lipids and aroma profiles of highland barley flour (HBF) were investigated in this study. Thermal stabilization significantly decreased the contents of ash and GABA. Baked HBF exhibited the lowest fatty acid value and peroxide value. Untreated HBF had higher lipase and lipoxygenase activities and fried mostly inactivated these enzymes. All thermal stabilization treatments increased the catalase activities and fried showed the higher level. Thus, fried might be an effective method to stabilize the HBF. The high temperatures during stabilizing triggered the complex reactions, leading to the loss of some volatile compounds, and in the meantime the formation of others such as furans and aldehydes. These productions contributed to the unique aroma profiles of different HBFs. Furthermore, a chemometric approach was used to analyze the changes of thermal stabilized treated HBFs and to identity six key volatile compounds, which provided important knowledge on possible chemical reactions caused by thermal stabilization. Overall, these results provide the theoretical basis for the wider application of thermal stabilization technologies in highland barley processing.

No abstract