刺槐二氧六环溶剂抽提物热诱导变色光谱分析

Spectrum analysis on heat-induced discoloration of dioxane extractives from locust(Robinia pseudoacacia) wood.

为探讨木材的受热变色机理,采用紫外光谱、红外光谱分析了二氧六环抽提物加热处理前后的发色体系结构变化;并对抽提前后木粉在模拟干燥条件下、加热处理前后进行了紫外漫反射光谱分析。结果表明:①抽出物含有黄酮类、可水解鞣质、香豆素等成分;加热后结构中羰基、羧基以及不饱和双键等发色基团数量增加,共轭发色体系电子跃迁能量降低,光谱吸收带延伸至可见光范围。②木粉中多酚类物质鞣质以及黄酮受热后易发生结构改变,这是木材受热后颜色变化的重要原因。③二氧六环抽提可除去部分具有醛、酮羰基等使木粉受热后颜色变深的物质,抽提后木粉在可见光区的吸收明显降低。

This study focuses on the mechanism of heat-induced wood discoloration.The UVVis spectra and FTIR spectra of the chromophoric system of dioxane extractives from locust(Robinia pseudoacacia) wood were compared and the analysis of diffusion UVVis reflection spectra of wood flours was conducted before and after the heating treatment.The results showed that the dioxane extractives consisted of flavonoids,hydrolysable tannins,coumarin and other components liable to discolor at high temperatures.Carbonyl(—CO),carboxyl(—COOH) and unsaturated linkage increased after the heating treatment,which resulted in a decrease of the electron transition energy,an increase of intensity and a red shift of the absorption band to the visible region.Structures of polyphenols,such as tannins and flavonoids,were apt to change during the heating treatment,which is the key reason for the wood discoloration.Part of the extractives with aldehyde groups and carbonyl groups which could lead to discoloration,could be removed by the extraction with dioxane and the absorption spectrum in the visible region was obviously reduced.