Modeling for aroma quality evaluation of Yunnan Pu-erh raw tea made from ancient trees based on principal component analysis

This study aimed to enhance the objectivity and scientificity of the aroma quality evaluation of Pu-erh raw tea made from ancient trees of Yunnan.A total of 94 volatile compounds were separated and identified from 13 tea samples by SPME and GC-MS.In addition, major characteristic aromatic components were identified by principal component analysis ( PCA) , which were Linalool and its oxides, Nerolidol, Geraniol, β-Ionone, Geranyl Acetone, ( Z) -2-Decenal, beta-Cyclocitral, Nonanal, ( E) -2-hexenyl ester Hexanoic acid, and Menthyl Salicylate.In addition, a PCA model for the aroma quality evaluation of Puerh raw tea made from ancient trees was constructed based on the comprehensive evaluation function: F = β₁F₁+ β₂F₂+ … +β_kF_k, which used the variance contribution rates of various eigenvalues βi ( i = 1, 2, ……, k) as weight coefficients.The model was used to calculate and rank aroma quality score of each tea sample for aroma quality evaluation.The evaluation results were in good agreement with those obtained from sensory evaluation, which indicated that it was feasible to use this model to evaluate the aroma quality of pu-erh raw tea made from ancient trees.