本实验以大豆分离蛋白(soy protein isolate,SPI)为原料,在不同挤压系统参数下对大豆分离蛋白进行挤压,通过测定蛋白质溶解度、Zeta电位、粒径、蛋白质亚基及蛋白质二级结构,研究挤压温度、物料水分质量分数和螺杆转速条件对大豆蛋白构...本实验以大豆分离蛋白(soy protein isolate,SPI)为原料,在不同挤压系统参数下对大豆分离蛋白进行挤压,通过测定蛋白质溶解度、Zeta电位、粒径、蛋白质亚基及蛋白质二级结构,研究挤压温度、物料水分质量分数和螺杆转速条件对大豆蛋白构象的影响,揭示大豆拉丝蛋白形成机理。结果表明,随着挤压温度升高,SPI天然结构被破坏,内部巯基基团暴露,二硫键含量的增加促使蛋白形成团聚体,过高或过低的温度均不利于蛋白质聚集和形成稳定状态;在过低或过高物料水分质量分数条件下,挤出模口难以形成较完整的挤出物,物料水分质量分数在20%~22%时因水的保护作用使得挤出物状态最佳,形成体系均一的SPI聚集体。较低的螺杆转速(130 r/min以下)会使机械能输入不足,蛋白质不能完全变性和解聚;较高的螺杆转速(140 r/min以上)条件下,高剪切力促进了蛋白质原有天然结构的破坏,形成了分子质量较大的蛋白质聚集体。综上,在适当的挤出条件下挤压处理有助于获得最佳的挤出物品质,过于极端的挤出条件会造成挤出物成型困难或质地不均匀。本研究可为大豆拉丝蛋白品质优化提供理论依据。展开更多
A prompt gamma neutron activation analysis(PGNAA)set-up was developed for the elements detection in aqueous solution,which includes a 241Am-Be neutron source and a 4-inch BGO detector.The geometry of set-up is determi...A prompt gamma neutron activation analysis(PGNAA)set-up was developed for the elements detection in aqueous solution,which includes a 241Am-Be neutron source and a 4-inch BGO detector.The geometry of set-up is determined by a series of simulations with the MOCA code to improve the efficiency of the elements detection.The thermal neutron flux and the gamma-ray self-absorption are considered during the optimization calculations.Experiments were performed to validate the set-up using samples including chlorine and mercury,respectively.The result shows that the characteristic peak count has linear relationship with the chlorine and mercury concentration changing.The minimum detectable concentrations of chlorine and mercury were found as 54 mg/L and 51.4 mg/L,respectively.展开更多
文摘本实验以大豆分离蛋白(soy protein isolate,SPI)为原料,在不同挤压系统参数下对大豆分离蛋白进行挤压,通过测定蛋白质溶解度、Zeta电位、粒径、蛋白质亚基及蛋白质二级结构,研究挤压温度、物料水分质量分数和螺杆转速条件对大豆蛋白构象的影响,揭示大豆拉丝蛋白形成机理。结果表明,随着挤压温度升高,SPI天然结构被破坏,内部巯基基团暴露,二硫键含量的增加促使蛋白形成团聚体,过高或过低的温度均不利于蛋白质聚集和形成稳定状态;在过低或过高物料水分质量分数条件下,挤出模口难以形成较完整的挤出物,物料水分质量分数在20%~22%时因水的保护作用使得挤出物状态最佳,形成体系均一的SPI聚集体。较低的螺杆转速(130 r/min以下)会使机械能输入不足,蛋白质不能完全变性和解聚;较高的螺杆转速(140 r/min以上)条件下,高剪切力促进了蛋白质原有天然结构的破坏,形成了分子质量较大的蛋白质聚集体。综上,在适当的挤出条件下挤压处理有助于获得最佳的挤出物品质,过于极端的挤出条件会造成挤出物成型困难或质地不均匀。本研究可为大豆拉丝蛋白品质优化提供理论依据。
基金supported by the National Natural Science Foundation of China(Grant No.11375087)National Key Scientific Instrument and Equipment Development Projects(Grant No.2013YQ40861)
文摘A prompt gamma neutron activation analysis(PGNAA)set-up was developed for the elements detection in aqueous solution,which includes a 241Am-Be neutron source and a 4-inch BGO detector.The geometry of set-up is determined by a series of simulations with the MOCA code to improve the efficiency of the elements detection.The thermal neutron flux and the gamma-ray self-absorption are considered during the optimization calculations.Experiments were performed to validate the set-up using samples including chlorine and mercury,respectively.The result shows that the characteristic peak count has linear relationship with the chlorine and mercury concentration changing.The minimum detectable concentrations of chlorine and mercury were found as 54 mg/L and 51.4 mg/L,respectively.
