Fractionation and identification of minor and aroma-active constituents in Kangra orthodox black tea

Abstract

The aroma constituents of Kangra orthodox black tea were isolated by simultaneous distillation extraction (SDE), supercritical fluid extraction and beverage method. The aroma-active compounds were identified using gas chromatography-olfactometry-mass spectrometry. Geraniol, linalool, (Z/E)-linalool oxides, (E)-2-hexenal, phytol, β-ionone, hotrienol, methylpyrazine and methyl salicylate were major volatile constituents in all the extracts. Minor volatile compounds in all the extracts were 2-ethyl-5-methylpyrazine, ethylpyrazine, 2-6,10,14-trimethyl-2-pentadecanone, acetylfuran, hexanoic acid, dihydroactinidiolide and (E/Z)-2,6-nonadienal. The concentrated SDE extract was fractionated into acidic, basic, water-soluble and neutral fractions. The neutral fraction was further chromatographed on a packed silica gel column eluted with pentane and diethyl ether to separate minor compounds. The aroma-active compounds identified using gas chromatography-olfactometry-mass spectrometry were 2-amylfuran, (E/Z)-2,6-nonadienal, 1-pentanol, epoxylinalool, (Z)-jasmone, 2-acetylpyrrole, farnesyl acetone, geranyl acetone, cadinol, cubenol and dihydroactinidiolide. AEDA studies showed 2-hexenal, 3-hexenol, ethylpyrazine, (Z/E)-linalool oxides, linalool, (E/Z)-2,6-nonadienal, geraniol, phenylethanol, β-ionone, hotrienol and dihydroactinidiolide to be odour active components.

Keywords: Extraction; Fractionation; Minor components; Odour impact; Orthodox black tea; Pyrazines.