Analysis of Changes in Quality Indicators during Storage of Raw Pu-Erh Tea
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Abstract:
In this study, 18 raw Pu-erh tea samples with storage times of 3 to 20 years were selected to investigate the changes in quality indicators of raw Pu-erh tea during storage through sensory evaluation and physicochemical composition analysis. The results showed that with increasing storage time, the color of raw Pu-erh tea gradually deepened, while the fresh aroma transformed into an aged fragrance. Simultaneously, the flavor changed from mellow and rich to mellow and neutral, and the color of the leaf bottom turned darker. The sensory quality was seen to improve after storage for 10 years and above, but began to decline after 18 years of storage. The water extract components, caffeine, GC, C, and CG showed irregular changes, while the concentration of gallic acid gradually increased. The contents of free amino acids, EGC, EC, EGCG, GCG, and ECG showed a decreasing trend with increasing storage time. Seventeen quality indicators were standardized and the samples were subjected to correlation analysis, principal component analysis, and cluster analysis that revealed significant correlations among the quality indicators. The tea samples could be divided into five categories by systematic clustering and could be clustered into one category every 3~4 years. In particular, category A had the highest composite score, followed by category D, while category E had the lowest score. Although the quality indicators show a decreasing trend with the increase in number of storage years, they remained stable during 3~4 years of storage. The results provide a basis for an in-depth study on the quality changes of raw Pu-erh tea during storage.
