To compare mid-infrared(MIR)and near-infrared(NIR)spectroscopies for the determination of the fat and protein contents in milk,the same sample sets with varying concentrations of fat and protein were measured in the M...To compare mid-infrared(MIR)and near-infrared(NIR)spectroscopies for the determination of the fat and protein contents in milk,the same sample sets with varying concentrations of fat and protein were measured in the MIR range of 3 200-700 cm-1 and NIR range of 9 000-4 000 cm-1.The spectral features in the two regions were analyzed.The MIR spectra of milk were characteristic due to the MIR inherent molecular specificity,whereas the NIR spectra were relatively characterless due to the NIR low selectivity.Partial least squares(PLS)regression models for fat and protein were developed by using both MIR and NIR spectra.MIR data with no pretreatment gave better results than NIR data.The square correlation coefficient(R2)and the root mean square error of prediction(RMSEP)were 0.98 and 0.10 g/dL for fat and 0.97 and 0.11 g/dL for protein.With NIR techniques,satisfactory results were not obtained with raw data.However,NIR data after pretreatment gave similarly good results to the ones using MIR method.This paper indicates that either of the MIR and NIR spectral methods is reliable for the determination of the fat and protein contents.展开更多
本研究以DPPH自由基清除能力为抗氧化活性衡量指标,利用双因素实验设计研究方法,探究了高压脉冲电场(PEF)的电场强度(5、10、15、20 k V/cm)和脉冲频率(1800、2400 Hz)两个因素对抗氧化肽MMCTN的抗氧化活性的影响,并且考察了PEF处理后...本研究以DPPH自由基清除能力为抗氧化活性衡量指标,利用双因素实验设计研究方法,探究了高压脉冲电场(PEF)的电场强度(5、10、15、20 k V/cm)和脉冲频率(1800、2400 Hz)两个因素对抗氧化肽MMCTN的抗氧化活性的影响,并且考察了PEF处理后保留时间(0、2 h)对其抗氧化活性的作用;借助傅立叶红外光谱技术(MIR)、圆二色谱技术(CD)分析了PEF处理对MMCTN的二级结构影响情况。研究发现,当电场强度为10 k V/cm,脉冲频率为2400 Hz,且PEF处理后保留2 h时,MMCTN的DPPH自由基清除能力最高,达到94.14%±0.13%;MIR光谱分析得知高压脉冲电场处理的样品功能团发生了改变;CD色谱分析得知PEF处理后的样品中α螺旋、β折叠、β转角和无规则卷曲之间发生了相互的转化。展开更多
基金Supported by National Natural Science Foundation of China(No.30170261)the 10th Five-Year Plan of China(No.2004BA706B12).
文摘To compare mid-infrared(MIR)and near-infrared(NIR)spectroscopies for the determination of the fat and protein contents in milk,the same sample sets with varying concentrations of fat and protein were measured in the MIR range of 3 200-700 cm-1 and NIR range of 9 000-4 000 cm-1.The spectral features in the two regions were analyzed.The MIR spectra of milk were characteristic due to the MIR inherent molecular specificity,whereas the NIR spectra were relatively characterless due to the NIR low selectivity.Partial least squares(PLS)regression models for fat and protein were developed by using both MIR and NIR spectra.MIR data with no pretreatment gave better results than NIR data.The square correlation coefficient(R2)and the root mean square error of prediction(RMSEP)were 0.98 and 0.10 g/dL for fat and 0.97 and 0.11 g/dL for protein.With NIR techniques,satisfactory results were not obtained with raw data.However,NIR data after pretreatment gave similarly good results to the ones using MIR method.This paper indicates that either of the MIR and NIR spectral methods is reliable for the determination of the fat and protein contents.
文摘本研究以DPPH自由基清除能力为抗氧化活性衡量指标,利用双因素实验设计研究方法,探究了高压脉冲电场(PEF)的电场强度(5、10、15、20 k V/cm)和脉冲频率(1800、2400 Hz)两个因素对抗氧化肽MMCTN的抗氧化活性的影响,并且考察了PEF处理后保留时间(0、2 h)对其抗氧化活性的作用;借助傅立叶红外光谱技术(MIR)、圆二色谱技术(CD)分析了PEF处理对MMCTN的二级结构影响情况。研究发现,当电场强度为10 k V/cm,脉冲频率为2400 Hz,且PEF处理后保留2 h时,MMCTN的DPPH自由基清除能力最高,达到94.14%±0.13%;MIR光谱分析得知高压脉冲电场处理的样品功能团发生了改变;CD色谱分析得知PEF处理后的样品中α螺旋、β折叠、β转角和无规则卷曲之间发生了相互的转化。
