紫花苜蓿挥发性成分萃取条件优化与定性、定量分析

Optimization of extraction conditions and qualitative and quantitative analysis of volatile components of alfalfa

挥发性成分是判断苜蓿干草品质优劣的基本感官指标,苜蓿干草在贮藏过程中受环境变化和微生物的作用,挥发性成分发生明显改变,直接影响苜蓿干草的适口性。目前我国牧草行业内缺乏针对苜蓿干草挥发性成分的分析鉴定方法,为此本研究采用顶空固相微萃取–气相色谱–质谱联用法(HS–SPME–GC–MS)分析紫花苜蓿(Medicago sativa)挥发性成分,结合峰面积归一化法确定各化合物的相对含量。结果表明:萃取温度90℃、萃取时间80 min、解析温度250℃、解析时间3 min为最佳萃取条件。该萃取条件下紫花苜蓿中共检测出52种化合物,包括酮类化合物9种,占总挥发物的37.55%;醇类化合物12种,占总挥发物的21.74%;醛类化合物15种,占总挥发物的19.31%;酯类化合物6种,占总挥发物的9.41%。其中β-紫罗兰酮含量可达到总挥发物的20%左右,苯乙醇、反式-2-己烯醛、2-苯基乙醛、壬醛、癸醛、6-甲基-5-庚烯-2-酮、3,5,5-三甲基环己-2-烯酮、胡薄荷酮等对紫花苜蓿挥发性成分贡献较大。

Volatile components are the basic sensory indicators of the quality of alfalfa hay,which is subject to environmental changes and microbial effects during storage,resulting in significant changes in the volatile components,directly affecting the palatability of alfalfa hay.At present,there is a lack of analytical methods to identify the volatile components of alfalfa hay in China’s forage industry.So,this experiment used headspace solid phase microextraction–gas chromatography–mass spectrometry(HS–SPME–GC–MS)to analyze the volatile components of alfalfa(Medicago sativa),combined with areas of peak.Normalization method determines the relative content of each compound.The results showed that an extraction temperature of 90℃,extraction time of 80 min,desorption temperature of 250℃,and desorption time of 3 min are the best extraction conditions.A total of 52 compounds were detected in alfalfa under these extraction conditions,including 9 ketones,accounting for 37.55%of the total volatiles,12 alcohols,accounting for 21.74%of the total volatiles,and 15 aldehydes,accounting for 19.31%of the total volatile matter,6 kinds of ester compounds,accounting for 9.41%of the total volatile matter.The content ofβ-ionone can reach about 20%of the total volatiles,phenethyl alcohol,trans-2-hexenal,2-phenylacetaldehyde,nonanal,decanal,6-methyl-5-heptene-2-ketones,3,5,5-trimethylcyclohex-2-enone,menthone,etc.contribute significantly to the volatile components of alfalfa.