为探究不同海拔南川大树红茶挥发性物质特征,采用顶空固相微萃取联用气相色谱-质谱技术结合多元分析方法对其鲜叶及成茶挥发性代谢物进行分析。从鲜叶中检测出15类,574种物质,红茶中检测出16类,575种物质;不同海拔鲜叶中挥发性代谢物总...为探究不同海拔南川大树红茶挥发性物质特征,采用顶空固相微萃取联用气相色谱-质谱技术结合多元分析方法对其鲜叶及成茶挥发性代谢物进行分析。从鲜叶中检测出15类,574种物质,红茶中检测出16类,575种物质;不同海拔鲜叶中挥发性代谢物总量差异不显著。经萎凋、发酵、干燥等工序加工成红茶后,其香气较鲜叶明显丰富,其含量较高的物质类型是酯类、杂环类、萜类、醛类和醇类;而低海拔红茶(low attitude-congou black tea,LA-CB)挥发性物质含量达148.67μg/g,显著高于高海拔红茶(high attitude-congou black tea,HA-CB)(104.27μg/g)。经正交偏最小二乘法判别分析,分别从鲜叶组和红茶组中筛选出113种、179种差异代谢物,并对红茶组差异代谢进行风味注释,建立了差异代谢物风味轮,得出不同海拔茶园的南川大树红茶香气品质主要表现为果甜香,同时高含量的挥发性代谢物使低海拔红茶香气表现为更浓郁而持久,该结果与感官审评一致。而对代谢物相对气味活度值进一步分析发现,2-异丙基-3-甲氧基吡嗪、5-乙基-3-羟基-4-甲基-2(5H)-呋喃酮、苯甲硫醇、6-壬烯醛、二乙基二硫醚等物质可能是南川大树红茶独特香气品质的重要贡献物质,其中2-异丙基-3-甲氧基吡嗪具有坚果、豆、巧克力风味,推测是红茶成茶香气特征区别于其鲜叶的重要物质。该研究为不同海拔南川大树红茶特征品质区分及香气品质形成成因提供理论参考。展开更多
The rheological characteristic of soy protein isolate(SPI),is one of the most important properties in its application in food industry.The effects of different concentrations of guar gum(GG,polysaccharide)and sodium c...The rheological characteristic of soy protein isolate(SPI),is one of the most important properties in its application in food industry.The effects of different concentrations of guar gum(GG,polysaccharide)and sodium chloride(salt ion)on the rheological properties of SPI were studied in this research.Steady-state shear,strain sweep and frequency sweep tests(static and dynamic rheological tests)were performed,and the following phenomenon and conclusions were drawn:(1)The viscosity of the hybrid system increases with the GG addition.This trend could also be seen with the appropriate adding of salt ion;(2)As the applied frequency increases,the storage modulus G′and the loss modulus G″of the hybrid system increase at a similar rate.And the frequency sweep parameters of the hybrid system rise significantly with the increase of both GG and ionic concentration;The frequency dependence of the system varies significantly with the addition of salt ion;(3)With the concentration of the salt ion increase,the storage module G′of the hybrid system decrease indicating that salt ion destroyed the network structure of hybrid dispersion to a certain extent.展开更多
文摘为探究不同海拔南川大树红茶挥发性物质特征,采用顶空固相微萃取联用气相色谱-质谱技术结合多元分析方法对其鲜叶及成茶挥发性代谢物进行分析。从鲜叶中检测出15类,574种物质,红茶中检测出16类,575种物质;不同海拔鲜叶中挥发性代谢物总量差异不显著。经萎凋、发酵、干燥等工序加工成红茶后,其香气较鲜叶明显丰富,其含量较高的物质类型是酯类、杂环类、萜类、醛类和醇类;而低海拔红茶(low attitude-congou black tea,LA-CB)挥发性物质含量达148.67μg/g,显著高于高海拔红茶(high attitude-congou black tea,HA-CB)(104.27μg/g)。经正交偏最小二乘法判别分析,分别从鲜叶组和红茶组中筛选出113种、179种差异代谢物,并对红茶组差异代谢进行风味注释,建立了差异代谢物风味轮,得出不同海拔茶园的南川大树红茶香气品质主要表现为果甜香,同时高含量的挥发性代谢物使低海拔红茶香气表现为更浓郁而持久,该结果与感官审评一致。而对代谢物相对气味活度值进一步分析发现,2-异丙基-3-甲氧基吡嗪、5-乙基-3-羟基-4-甲基-2(5H)-呋喃酮、苯甲硫醇、6-壬烯醛、二乙基二硫醚等物质可能是南川大树红茶独特香气品质的重要贡献物质,其中2-异丙基-3-甲氧基吡嗪具有坚果、豆、巧克力风味,推测是红茶成茶香气特征区别于其鲜叶的重要物质。该研究为不同海拔南川大树红茶特征品质区分及香气品质形成成因提供理论参考。
基金supported by the Research Foundation for Youth Scholars of Beijing Technology and Business University(QNJJ2016-17)supported by the National Natural Science Foundation of China(31301593)Research and Development Fund for University’s Doctoral Discipline of China(20130008120021).
文摘The rheological characteristic of soy protein isolate(SPI),is one of the most important properties in its application in food industry.The effects of different concentrations of guar gum(GG,polysaccharide)and sodium chloride(salt ion)on the rheological properties of SPI were studied in this research.Steady-state shear,strain sweep and frequency sweep tests(static and dynamic rheological tests)were performed,and the following phenomenon and conclusions were drawn:(1)The viscosity of the hybrid system increases with the GG addition.This trend could also be seen with the appropriate adding of salt ion;(2)As the applied frequency increases,the storage modulus G′and the loss modulus G″of the hybrid system increase at a similar rate.And the frequency sweep parameters of the hybrid system rise significantly with the increase of both GG and ionic concentration;The frequency dependence of the system varies significantly with the addition of salt ion;(3)With the concentration of the salt ion increase,the storage module G′of the hybrid system decrease indicating that salt ion destroyed the network structure of hybrid dispersion to a certain extent.
