Comparison of microwave and conventional heating on physicochemical properties and phenolic profiles of purple sweetpotato and wheat flours

The hydrothermal treatment assisted with microwaves on physicochemical properties and phenolic profiles of purple sweetpotato flour and wheat flour was studied and compared with those of conventional heat treatment.Both treatments significantly decreased the enthalpy change,pasting viscosity and gelling capacity of flours,while increasing particle size,gelatinization temperatures and content of resistant starch.Microwaves induced more severe damages on the starch granule morphology and crystallinity than conventional heat treatment,which could be attributed to the intensive friction and collision produced by electromagnetic waves.The total concentrations of hydroxycinnamic acid derivatives and anthocyanins in purple sweetpotato flour extracted using microwaves at 100℃ were 36%and 68%higher than those in the samples after conventional heat treatment at 100℃,respectively.Electromagnetic waves caused a higher extent of cell damage due to sudden temperature rise during microwave treatment.Overall,microwave treatment has potential to produce novel functionalities and nutritional values of flours and can be applied as an effective approach for other starch-based food products.

Microwave-assisted synthesis of new pyrimido[4′,5′:4,5]thiazolo[3,2-a]benzimidazol-4(3H)-one derivatives in solvent-free condition

Microwave-assisted synthesis of new 2-arylpyrimido[4′,5′：4,5]thiazolo[3,2-α]benzimidazol-4（3H）-ones from 3-aminothia- zolo[3,2-α]benzimidazol-2-earboxamide and aroyl halides in solvent-free condition is described. In comparison with classical conditions the reactions are faster and the yields are higher under microwave irradiation.

Synthesis of Novolacs under Microwave Irradiation

Novolacs were successfully synthesized using oxalic acid as the catalyst in a self-designed device based on a domestic microwave oven, The fundamental characteristics of the synthesis of novolacs under microwave irradiation （MI） were investigated, and the properties of the resins polymerized and dehydrated under microwave irradiation and conventional heating （CH） were analyzed comparatively, The results show that MI reduced the polymerization and dehydration time greatly; and that the resins polymedzed and dehydrated under MI presented longer flow distances （ i. e., higher flowability） and shorter cure time than those obtained under CH.

Effect of Microwave Irradiation on Oximation of Acetylferrocene

Microwave-assisted reactions are an environmentally friendly approach for synthesizing organic compounds. In this study, oximation of acetylferrocene and acetophenone was conducted under both microwave irradiation and conventional heating conditions. Acetylferrocene and acetophenone were subjected to oximation under the two conditions in various solvent mixtures, and the extent of conversion was determined by 1H nuclear magnetic resonance spectroscopy. Microwave irradiation was found to accelerate the rate of oximation of both acetylferrocene and acetophenone. Acceleration of the reaction under microwave irradiation was attributed to the efficient absorption of microwaves by the ferrocene nucleus.

Solid-Phase Decarburization of High-Carbon Ferromanganese Powders by Microwave Heating

The solid-phase decarburization of high-carbon ferromanganese powders （HCFPs） was investigated using calcium carbonate as the decarburizer by microwave heating and conventional heating methods to explore the differ-ences of microwave heating and conventional heating. Experimental results show that HCFPs containing calcium.car-bonate were heated up to 900, 1000, 1 100, and 1200 ℃ and held for 60 rain for decarburization by microwave heat-ing at decarburization ratios of 76.69%, 82.90%, 84.11%, and 85. 75%, respectively. These ratios are higher than the decarburization ratios used for conventional heating under the same experimental conditipns. The microwave heat- ing can significantly improve decarburization ratio. This indicates the microwave heating field features a non-thermal effect, which in turn, visibly enhances the carbon diffusion ability of HCFPs. It also improves the kinetic conditions of solid-phase decarburization.