低温对磷化氢熏蒸长角扁谷盗致死时间延迟影响的研究

为研究不同冻结温度对米发糕品质特性的影响，本研究采用-18、-30、-80和-196 ℃四种冻结温度处理，对冷冻曲线、失水率、质构特性、白度、淀粉老化、电子舌、电子鼻、GC-MS及感官评定等进行分析。结果表明：米发糕的冻结温度越低，越能有效缩短冻结时间，减小冻结损伤，降低失水率和米发糕的淀粉老化焓值。且-196 ℃组的白度值、质构特性与鲜样最接近，均显著优于其它三组（p≤0.05）。此外电子舌与电子鼻的PCA图显示冻结温度越低，其主成分阈值越接近鲜样。GC-MS数据表示冻结处理会降低米发糕总体醇类物质含量，其中-80℃组的醇类含量最高。米发糕经冻结处理后复蒸，其感官评分会相应下降，冻结温度越低感官评分越高。以上结果表明，-196 ℃冻结可以更好地保持冷冻米发糕的品质特性。

Influence of low temperature on the lethal time delay in phosphine fumigation of Cryptolestes pusillus Schoenherr

KF-MgO solid base catalyst was prepared from potassium fluoride dihydrate and magnesium acetate (tetrahydrate) by mixing, grinding and roasting. The optimal preparation conditions for the single-factor experiment are : n(KF.2H₂O) : n(MgAc₂.4H₂O)=1, roasting temperature 500 degrees C, roasting time 3h. The solid alkali catalyst produced under the above conditions is used to catalyze the ester exchange reaction of castor oil and methanol, and the refractive index of biodiesel is 1.4626 and the conversion rate of castor oil is 96.36%. The KF-MgO solid alkali catalyst and its precursor prepared under optimal conditions are characterized by thermal weight analysis, scanning electroscope and X-ray diffraction, and the results show that: The decomposition process of the precursor of KF-MgO solid base catalyst is basically completed at about 500 degrees C. The catalyst is mainly in the form of KMgF₃, which is honeycomb with a certain number of holes.