Identification of potent odourants in static headspace samples of green and black tea powders on the basis of aroma extract dilution analysis (AEDA)

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Abstract
Aroma extract dilution analysis (AEDA) of the volatile fractions of green and black tea samples revealed 28 odourants of which 27 were identified. As the odour quality and the chromatographic properties of most of the odourants occurring in the air above the tea powders agreed with those which were identified by the preceding AEDA, these compounds were detectable by gas chromatography–olfactometry (GC–O) in static headspace samples. (Z)‐Hex‐3‐enal, linalol, (Z)‐octa‐1,5‐dien‐3‐one, oct‐1‐en‐3‐one, (Z)‐hept‐4‐enal, butane‐2,3‐dione, 2‐methylpropanal, 3‐methylbutanal, 3‐methylnonane‐2,4‐dione, (E)‐non‐2‐enal, octanal, (E,Z)‐nona‐2,6‐dienal and hexanal were found in the headspace volume of 40 ml which was drawn at 40°C from both kinds of tea. (E, E)‐Nona‐2,4‐dienal and α‐pinene were detected as additional odourants of black tea. The most potent odourants occurring in the air above the tea powders were evaluated by the analysis of decreasing headspace volumes, e.g. (Z)‐hex‐3‐enal was the sole odourant in 2 ml of the headspace of green tea and linalol in 0.5 ml of that of black tea. This procedure indicated that the difference in the odours of green and black tea was mainly due to a higher concentration of (Z)‐hex‐3‐enal, (Z)‐octa‐1,5‐dien‐3‐one and butane‐2,3‐dione and the much lower concentration of linalol in the air above the former.

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