Scenting Processes for Quality Improvement of Osmanthus Green Tea

Objective Effects of scenting process on quality of osmanthus green tea (OGT) were analyzed.

Method Sensory evaluation, biochemical determination, and automatic thermal desorption-gas chromatography-mass spectrometry (ATD-GC-MS) were conducted on raw tea leaves, scented OGTs, and a traditional OGT. The scented OGTs made by using various scenting processes were all judged by the sensory panel to be significantly superior to the traditionally OGT in quality.

Result The contents of water extracts, tea polyphenols, free amino acids, and caffeine were 48.60%, 19.30%, 4.47%, and 3.10%, respectively, in the scented OGTs, while 48.47%, 19.80%, 4.50%, and 3.17%, respectively, in the traditional product. Forty aromatics including alcohols, ketones, esters, aldehydes, alkenes, and other volatiles were isolated from the various samples. The contents of isovalerate, nerol, and β-ionone of the floral, fresh fruit, and ripe apple aroma type were significantly higher in the traditional OGT than in the tea leaves. On the other hand, the scented OGTs had significantly lower relative content of 1-octen-3-ol that is characterized as lavender and rose fragrance than did the leaves from which they were made. But nerol and β-ionone were significantly higher in the scented than the traditional OGT. The scenting processes also significantly accentuated the relative contents of the rose and orange flower aroma-related nerolidol, the violet and floral fragrance-related β-ionone, and the sweet violet fragrance-related 5,6-epoxy-β-ionone in OGTs. The significantly affected biochemistry, specifically aromatic compounds, elevated the sensory quality of OGT.

Conclusion In particular, the “one-scenting + one-scenting and one-extraction” process was deemed superior for the tea making. Among the aromatics isolated, nerol and β-ionone were believed to be the major components that characterized the scented OGTs.