新年的香味！基于UHPLC-MS/MS揭示咖啡豆烘焙过程中脂质的动态变化

2.5 质量控制(Qc)

●  3. 结果与讨论  ●

     脂质提取作为样品制备中的关键步骤，对于降低样品的复杂性和富集感兴趣的化合物具有重大影响。四种溶剂分别提取咖啡豆的脂质如Fig. 1所示，正离子模式和负离子模式下的总离子色谱（TIC）峰强度分别为Fig. 1A 和1B，可以看出MeOH/CH₂Cl₂ (2:1,v/v )提取的咖啡豆中脂质的TIC强度是Z高的，Fig. 1C显示了四种提取溶剂的化学特征总量，这表明用MeOH/CH₂Cl₂ (2:1,v/v )提取的脂质样品中获得了Z高数量的化学特征。综合考虑脂质覆盖率和响应强度，选择MeOH/CH₂Cl₂ (2:1,v/v )作为提取咖啡豆脂质的Z合适溶剂。

Fig. 1. Total ion chromatography peak intensity of lipids detected of roasted coffee bean extracted by different solvents, in both (A) positive mode and (B)negative mode, (C) total number of chemical features.

Fig. 2. MS/MS fragmentation pathway of: (A) PC (16:0_18:2) (m/z 758.5694) in ESI (+) mode (B) PI (16:0_18:2) (m/z 833.5266) in ESI (-) mode; (C) TAG (16:0_18:2_18:2) (m/z 854.7363) in ESI (+) mode. PC: Phosphatidylcholine; PI:Phosphatidylinositol; TAG: Triacylglycerol.

Fig. 3. Lipid composition (%) of coffee bean at different roasting times. (A) 0 min; (B) 4 min; (C) 8 min; (D) 12 min; (E) 16 min.

Fig. 4. Heatmap of the metabolic variations of individual lipid subclasses during coffee bean roasting process.

Fig. 5. Trends of characteristic lipids during the roasting process. (A) PC (16:0_18:2); (B) PI (16:0_18:2); (C) TAG (16:0_18:2_18:2); (D) DAG (16:0_18:2). PC: Phosphatidylcholine; PI: Phosphatidylinositol; TAG: Triacylglycerol; DAG: Diacylglycerol.

Fig. 6. The score plots of orthogonal partial least squares discrimination analysis (OPLS-DA) pairwise comparisons of different groups of coffee bean. (A) 0 min vs. 4 min; (B) 4 min vs. 8 min; (C) 8 min vs. 12 min; (D) 12 min vs. 16 min.

Fig. 7. Upregulated and downregulated differential lipids in pairwise comparison. Red indicates an upward adjustment and green indicates a downward adjustment. (A) 0 min vs. 4 min; (B) 4 min vs. 8 min; (C) 8 min vs. 12 min; (D) 12 min vs. 16 min.