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

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 of β-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.