Evaluating the Impact of Various Drying Processes on the Comprehensive Properties of Thyme Powder (Thymus vulgaris) for Retention of Its Bioactive Properties

Thyme (Thymus vulgaris) was dried using a tray dryer, recirculating tray dryer, and vacuum dryer at 35 °C, 40 °C, and 45 °C, respectively. The dried thyme after attaining 5% moisture content was subjected to a grinding process to obtain powder using a hammer mill for further analysis of physiochemical properties, bioactive compounds, and techno-functional properties. The ash content was 10.21%, fiber content was 13.57%, fat content was 1.69%, protein content was 5.61%, and carbohydrate content was 22.91% for the thyme sample dried at 35 °C via vacuum drying. Meanwhile, regarding the functional properties, the swelling power was 0.31%, dispersibility was 27.72%, emulsion capacity was 35.44%, foam capacity was 35.47%, and foam stability was 1.84% for the thyme sample dried at 40 °C in the vacuum dryer. The total chlorophyll content, ascorbic acid content, and bioactive compounds were retained best in the vacuum-dried sample at 40 °C. Bioactive compound retention for VDT among the selected three techniques at 35 °C was considerably better. The color values were found to be similar to those of freshly harvested thyme (hue, 93.39; chroma, 3.47) for the thyme sample dried at 40 °C in a vacuum dryer. Based on the analysis, it was found that vacuum drying at 40 °C gave better results, followed by the recirculating tray dryer at 40 °C and the tray dryer at 40 °C. The adequately dried thyme samples with the time–temperature combinations for different drying techniques used can be used further for product development and studies on their shelf life.