光谱分析法应用于咖啡成分的测定和咖啡种类的鉴别

应用光谱分析法测定现磨咖啡、速溶咖啡和菊苣咖啡的成分。通过电感耦合等离子体发射光谱(ICP-ES)测定咖啡样品的矿物质元素。分别采用紫外(UV)和傅里叶红外(FTIR)光谱法测定咖啡因和有机物的含量，草酸的测定需要采用氧化还原滴定法来完成。基于咖啡因、草酸和矿物质的测定，分析现磨咖啡、速溶咖啡和菊苣咖啡的差异。实验表明，咖啡因在速溶咖啡中的含量比现磨咖啡的要高出2～3倍;草酸在速溶咖啡中的含量明显高于现磨咖啡;矿物质元素Mg，P，Zn在现磨咖啡中的含量比速溶咖啡的要低，而Cu的含量则比速溶咖啡高出好几倍;菊苣咖啡中的矿物质含量总体上比速溶咖啡的要低。此外，我们在不同种类的咖啡中测定Ti的含量，在菊苣咖啡中检测到Cu，Ti，Zn元素。作为一种快速检测技术，FTIR光谱可以用于鉴别现磨、速溶和菊苣咖啡，并能够检验咖啡因和草酸的存在。

Spectroscopic Methods Applied to Component Determination and Species Identification for Coffee

Spectroscopic analysis was applied to the determination of the nutrient quality of ground, instant and chicory coffees. By using inductively coupled plasma atomic emission spectrometry (ICP-ES), nine mineral elements were determined in solid coffee samples. Caffeine was determined by ultraviolet (UV) spectrometry and organic matter was investigated by Fourier transform infrared (FTIR) spectroscopy. Oxidation-reduction titration was utilized for measuring the oxalate. The differences between ground coffee and instant coffee was identified on the basis of the contents of caffeine, oxalate and mineral elements. Experimental evidence showed that, caffeine in instant coffee was 2-3 times higher than in ground coffee. Oxalate in instant coffee was significantly higher in ground coffee. Mineral elements of Mg, P and Zn in ground coffee is lower than in instant coffee, while Cu is several times higher. The mineral content in chicory coffee is overall lower than the instant coffee. In addition, we determined the content of Ti for different types of coffees, and simultaneously detected the elements of Cu, Ti and Zn in chicory coffee. As a fast detection technique, FTIR spectroscopy has the potential of detecting the differences between ground coffee and instant coffee, and is able to verify the presence of caffeine and oxalate.