Effect of decaffeination conditions on quality parameters of Kangra orthodox black tea

Effect of extraction temperature and pressure on the removal of caffeine from Kangra orthodox black tea using supercritical carbon dioxide was investigated. Maximum caffeine as well as volatile flavor components was extracted at 35 °C/170 bar using 60 g/min flow rate for 90 min extraction in dynamic mode. Satisfactory decaffeination and quality retention were achieved at extraction at 60 °C/90 bar. The quality of extracts reduced at higher extraction temperature and pressure combinations. Maximum amounts of theaflavins (88.88%), thearubigins (81.18%) and catechins (73.53%) were retained at these extraction conditions. Volatile components in original (caffeinated) and decaffeinated black teas were isolated by simultaneous distillation extraction (SDE), and analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). 2-Hexenal, 3-hexenol, phenylacetaldehyde, cis-linalool oxide, linalool, trans-geraniol, nerolidol, methyl salicylate, α- and β-ionones decreased in decaffeinated black teas compared to untreated control. β-ionone (1.77%), trans-linalool oxide (5.36%), linalool (7.84%), trans-geraniol (4.32%) and methyl salicylate (1.90%) were retained in satisfactory amount in decaffeination at 60 °C/90 bar. Application of aroma extract dilution analysis revealed 11 odor active compounds with flavor dilution (FD) factor ranging from 8 to 512 and odor quality investigated by GC-FID, GC-MS. Some unknown compounds quantitatively reduced or disappeared during decaffeination process. Although there was considerable loss of theaflavins and thearubigins as well as volatile flavor components, SFE extraction at 60 °C/90 bar for 90 min appears as the method suitable for selective removal of caffeine from the Kangra orthodox black tea.

► Decaffeination of black orthodox tea via supercritical fluid extraction. ► Decaffeination and quality retention were achieved at 60 °C/90 bar. ► trans-Linalool oxide, linalool and trans-geraniol were higher at 60 °C/90 bar. ► Aroma extract dilution analysis revealed 11 odour active compounds. ► Sensory analysis validated sweet, floral and fruity characters at 60 °C/90bar.