Aroma compounds in black tea powders of different origins-changes induced by preparation of the infusion

By application of the Aroma Extract Dilution Analysis on the volatiles of black tea leaves (Darjeeling Gold Selection, DG), linalool, β-ionone, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF), 3-hydroxy-4,5-dimethyl-2(5H)-furanone, phenylacetic acid and (E,E,Z)-2,4,6-nonatrienal were identified with the highest Flavour Dilution (FD) factors among the 25 odour-active compounds detected in the FD-factor range of 16 to 256. Quantitative measurements performed on the infusion prepared from DG indicated the same set of odorants as identified in the leaves, but the hot water treatment led to an increase of, in particular, most of the alcohols, i.e. geraniol, 4-HDF, 2-phenylethanol and (Z)-3-hexenol, as well as the Strecker aldehydes methylpropanal and 2-methylbutanal. Infusions prepared from four other black tea leaves of different origins also contained the same set of odorants as the infusion from DG, but the odorants identified varied significantly in their FD-factors.