黄酒类黑精的提取、成分及光谱特性研究

EXTRACTION, COMPOSITION AND SPECTRAL PROPERTIES OF MELANOIDINS FROM CHINESE RICE WINE

为进一步揭示黄酒的褐变机理,将不同年份黄酒进行乙醇丙酮分级沉淀、超滤、冷冻干燥,分别得到3个类黑精组分(MWCO>1 000),对其总氮含量、总糖含量、骨架肽段氨基酸组成、UVVis和FT-IR吸收光谱进行了研究。结果表明:黄酒陈化过程中,类黑精的总氮含量增加,总糖含量减少,说明游离氨基酸等氨基化合物逐渐参与类黑精形成,糖类参与生成羰基或二羰基中间体,并进一步与蛋白质骨架结合形成类黑精;其骨架肽段氨基酸组成的变化表明脯氨酸最具类黑精形成活性;其UV-Vis光谱呈现典型的"尾巴模式",紫外区有强吸收,吸光度随波长增大而逐渐减小;FT-IR光谱表明黄酒类黑精存在显著的酰胺Ⅰ带和糖类特征吸收带,酰胺Ⅱ带及Ⅲ带几乎消失表明其肽段骨架因Maillard反应改变了部分结构。

In order to further reveal the browning mechanism of Chinese rice wine,melanoidins（CRWM-1,CRWM-2 and CRWM-3） from Chinese rice wine produced in different years were separated by fraction precipitation using ethanol and acetone, and then subjected to ultrafiltration to obtain the fractions whose molecular weight larger than 1 000 Da. The nitrogen content,sugar content,amino acid composition,UV-Vis and FT-IR spectra of the fractions were investigated. The results showed that the nitrogen content increased while sugar content decreased during aging, which indicated that amino compounds such as free amino acids participated in forming melanoidins,sugars participated in forming carbonyl or dicarbonyl compounds and then combined with the protein skeleton to generate melanoidins. The change of amino acid composition of peptides skeleton showed that proline was easiest to form melanoidins. The UV-Vis spectra of melanoidins presented the typical ＂tail＂mode,which had a strong absorption in the ultraviolet region and absorbance decreased with the increasing wavelength. FT-IR spectra showed that melanoidins from Chinese rice wine had remarkable amide Ⅰband and saccharide bands. The almost disappeared amide Ⅱ and Ⅲ bands might indicate that partial structure of skeleton protein were changed due to maillard reaction.