Aroma-active compounds of Georgian black tea infusions as determined by gas chromatography-olfactometry

Aroma belongs to the most important quality characteristics of black tea infusions. Volatile aroma-active compounds were analysed in infusions of black tea produced in Georgia in two major production locations. For this purpose, solid phase microextraction was used to isolate the volatile fractions, which were subsequently analysed by gas chromatography-olfactometry and gas chromatography-mass spectrometry. The method used involves a combination of instrumental separation and sensory analysis by the human nose, which provide quantitative data to characterize the organoleptic quality and allow the detection of volatile compounds with strong aroma perception even if present at low concentration levels. Overall, 59 odouric zones were identified in the lowland black tea and 57 odouric zones were identified in the highland black tea. The aroma-active compounds comprised alcohols, aldehydes, terpenes, ketones, phenolics lactones, furanes, furanones and long chain fatty acids. Odorously most pronounced compounds in both Georgian black tea infusions were benzaldehyde, beta-ionone, delta-decalactone, (E)-linalool-3,7-oxide, furaneol, hexanal, indole and 2-phenylethanol. The results demonstrated that Georgian black tea is of good quality, being compatible with international requirements, while indicating specific components that might be interesting for its use in premium blends.