Coriander leaves are valued for their culinary, medicinal, and cosmetic benefits, yet their high perishability leads to considerable post-harvest losses. This study investigated the effects of four drying techniques, sun drying (SD), microwave drying (MD), cabinet drying (CD), and freeze drying (FD), on the physicochemical, nutritional, and bioactive characteristics of coriander leaves, as well as their applicability in vegetable soup preparation. CD and FD effectively preserved color parameters (L*, a*, b*), chlorophyll content, and showed minimal total color change (2.32 ± 0.26, 5.81 ± 1.26, respectively), whereas MD resulted in the greatest degradation (23.53 ± 2.19) due to high thermal stress. SD maintained the highest total phenolic content (120.26 ± 3.02 µg GAE/g DM), flavonoid content (64.33 ± 2.97 µg QE/g DM), and antioxidant activity (2.30 ± 0.063 µM TE/g DM), likely due to mild drying conditions. The strongest α-glucosidase inhibitory activity—indicating antidiabetic potential—was observed in CD-treated samples (0.071 ± 0.012 µM Acarbose/g DM). Multivariate analysis (PCA) and Pearson’s correlation revealed strong positive relationships among TPC, TFC, antioxidant activity, chlorophyll levels, and antidiabetic capacity. Sensory evaluation showed that CD-treated leaves offered the best aroma, taste, and overall acceptability, while SD and FD were preferred for their color and texture. Vegetable soups prepared with CD and SD leaves received the highest sensory scores, even surpassing those made with fresh leaves. In contrast, MD samples consistently showed poor performance in terms of nutrient retention, appearance, and flavor. Overall, cabinet drying emerged as the most effective method for preserving the functional, nutritional, and sensory qualities of coriander leaves, making it highly suitable for commercial dried herb applications and soup formulations.
Sarkar et al. (Thu,) studied this question.