采用质量浓度为5 m g/L的臭氧作为氧化剂,对糯米整米通气氧化后制作水磨糯米粉并且提取相对应的糯米淀粉。通过实验发现氧化后糯米粉及对应提取的糯米淀粉随着臭氧处理时间的增长糊化黏度呈增大趋势,但热糊稳定性和抗老化性有略许减弱,...采用质量浓度为5 m g/L的臭氧作为氧化剂,对糯米整米通气氧化后制作水磨糯米粉并且提取相对应的糯米淀粉。通过实验发现氧化后糯米粉及对应提取的糯米淀粉随着臭氧处理时间的增长糊化黏度呈增大趋势,但热糊稳定性和抗老化性有略许减弱,蒸煮特性未发生较大变化。羧基含量随着氧化时间的增长而增大,而羰基含量随着氧化时间的增长呈先增后减的趋势。通过红外光谱分析发现臭氧将糯米淀粉中葡萄糖单元上C2、C3和C6的羟基先氧化为羰基,随着氧化作用的加强羰基被氧化成为羧基,但由于是对于糯米的氧化处理,因此在反应中会生成部分酰胺,同时葡萄糖环中的C—O—C未发生断裂。展开更多
Enthalpy changes for the protonation of carboxyl group of four α amino acids(glycine,L α alanine,L valine and L serine) were measured in water ethanol mixtures (10－70wt％) at 298.15K using LKB 2277 Bioactivity Moni...Enthalpy changes for the protonation of carboxyl group of four α amino acids(glycine,L α alanine,L valine and L serine) were measured in water ethanol mixtures (10－70wt％) at 298.15K using LKB 2277 Bioactivity Monitor.The corresponding entropy and Gibbs energy changes were also calculated.The results show that both enthalpy changes and entropy changes are favorable to the protonation of carboxyl groups of the investigated amino acids in water ethanol mixtures.However,the influence of the composition of ethanol in the mixed solvents on the enthalpy change and entropy changes is complicated . Both and ,the differences of enthalpy changes and entropy changes in mixed solvents and in pure water respectively,show a minimum approximately at xEtOH=0.1.The effects of side chains on the enthalpy change and entropy changes were also investigated using the proton transfer process between glycine and the other three amino acids.The results demonstrate that the proton transfer processes for alanine and valine are spontaneous but not for serine,which could be interpreted in terms of the electrostatic interaction between amino group and carboxyl group within the molecule and the interaction between carboxyl group and the solvent.展开更多
文摘采用质量浓度为5 m g/L的臭氧作为氧化剂,对糯米整米通气氧化后制作水磨糯米粉并且提取相对应的糯米淀粉。通过实验发现氧化后糯米粉及对应提取的糯米淀粉随着臭氧处理时间的增长糊化黏度呈增大趋势,但热糊稳定性和抗老化性有略许减弱,蒸煮特性未发生较大变化。羧基含量随着氧化时间的增长而增大,而羰基含量随着氧化时间的增长呈先增后减的趋势。通过红外光谱分析发现臭氧将糯米淀粉中葡萄糖单元上C2、C3和C6的羟基先氧化为羰基,随着氧化作用的加强羰基被氧化成为羧基,但由于是对于糯米的氧化处理,因此在反应中会生成部分酰胺,同时葡萄糖环中的C—O—C未发生断裂。
文摘Enthalpy changes for the protonation of carboxyl group of four α amino acids(glycine,L α alanine,L valine and L serine) were measured in water ethanol mixtures (10－70wt％) at 298.15K using LKB 2277 Bioactivity Monitor.The corresponding entropy and Gibbs energy changes were also calculated.The results show that both enthalpy changes and entropy changes are favorable to the protonation of carboxyl groups of the investigated amino acids in water ethanol mixtures.However,the influence of the composition of ethanol in the mixed solvents on the enthalpy change and entropy changes is complicated . Both and ,the differences of enthalpy changes and entropy changes in mixed solvents and in pure water respectively,show a minimum approximately at xEtOH=0.1.The effects of side chains on the enthalpy change and entropy changes were also investigated using the proton transfer process between glycine and the other three amino acids.The results demonstrate that the proton transfer processes for alanine and valine are spontaneous but not for serine,which could be interpreted in terms of the electrostatic interaction between amino group and carboxyl group within the molecule and the interaction between carboxyl group and the solvent.
