Effects of Freeze Drying and Spray Drying Techniques on the Encapsulation of Black Tea Aroma Compounds

In this study, freeze drying and spray drying were evaluated as techniques for encapsulating the volatile compounds in the steam distillate of black tea. A mixture of carrier materials was prepared by dissolving 0.1 g of gum arabic and 9.9 g of maltodextrin in warm water, then mixing it with 1 L of steam distillate of black tea. The prepared mixture was divided into two portions: one portion was freeze-dried, and the other was spray-dried to produce encapsulated black tea aroma powders. The sensory properties of the freeze-dried black tea aroma powder (FD-BTA) and spray-dried black tea aroma powder (SD-BTA) were assessed using a pairwise comparison test with thirty semi-trained panellists. Aroma profiles of FD-BTA and SD-BTA were analysed by solid-phase microextraction-gas chromatography-mass spectrometry and gas chromatography-flame ionization detector techniques. The results indicated that FD-BTA had superior sensory properties compared to SD-BTA and contained 17 key volatile compounds, whereas SD-BTA contained only 8 compounds. FD-BTA retained high concentrations of tea aroma available in steam distillate, including linalool (262.64±33.88 mg/L) and methyl salicylate (190.02±28.58 mg/L). The encapsulation efficiencies of key black tea aroma compounds were significantly higher with freeze drying (linalool- 61.89±5.64%, methyl salicylate- 23.59±3.02%, geraniol- 39.45±6.92%, and β-ionone- 29.86±4.50%) than with spray drying (linalool- 4.93±0.25%, methyl salicylate- 0.70±0.10%, geraniol- 13.78±2.41%, and β-ionone- 13.86±1.88%). Overall, freeze drying was found to be more effective than spray drying for encapsulating aroma compounds in black tea steam distillate.