Effect of different drying treatments on the physicochemical, functional, and antioxidant properties of Bacopa monnieri

Bacopa monnieri (L.) Wettst is a very high-value medicinal plant that is commonly used for improving cognitive functions. However, the availability of very limited information on the drying method of B. monnieri has prompted to optimize a suitable drying method. The present study therefore aimed to evaluate the influence of the following six drying treatments on the quality of B. monnieri sample: microwave drying at 300 W and 600 W, hot air-drying at 50°C and 70°C, solar drying, and freeze-drying (FD). The quality attributes of the dried samples were comparatively analyzed in terms of color, total color difference, moisture content, water activity (a (w)), antioxidant activity, and bacoside A and bacopaside I content. The results of this study showed significant differences (P < 0.05) among the different drying methods in International Commission on Illumination (CIE) parameters, namely lightness index (L*), red-green index (a*), and yellow-blue index (b*), ΔE and a values. Among the samples dried with the six drying methods, freeze-dried B. monnieri samples had an attractive color with the lowest total color difference value (11.415%), a (w) value (0.15%), and maximum bacoside A (3.389%) and bacopaside I (0.620%) content. Moreover, Fourier transform infrared spectroscopy (FT-IR) analysis showed no major difference in the functional groups in B. monnieri samples processed by the different drying methods. Considering the retention of quality after drying, FD was found to be very effective for future large-scale production of good quality dried B. monnieri products.