Comparative Evaluation of Drying Methods on Structural, Elemental, Cytotoxic, and Antimicrobial Properties of Moringa...

This study investigated the influence of different drying methods on the structural characteristics, cytotoxic, and antimicrobial properties of Moringa oleifera pod pulp powder (MPP). Fresh, mature pods were processed under hygienic conditions, and the resulting powders were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy to elucidate functional group stability, microstructural morphology, and elemental retention, respectively. Cytotoxicity was assessed in human colon carcinoma (Caco-2) cells using trypan blue exclusion, neutral red uptake, and MTT reduction assays, while antimicrobial activity was determined against Staphylococcus aureus, Bacillus cereus, Pseudomonas fragi, and Salmonella typhi via agar well diffusion. The results revealed that FD preserved key hydroxyl, amide, and polysaccharide bands; maintained porous structure; and ensured the highest mineral retention (Ca, K, Mg, P). FD-treated MPP demonstrated superior cell viability (>95%) with no detectable cytotoxicity (p > 0.05) and exhibited the strongest antibacterial activity, with inhibition zones ranging up to 30 mm against B. cereus. Conversely, OD and SD samples showed reduced bioactivity and minor structural degradation due to prolonged thermal exposure. The enhanced functional and microbiological characteristics of freeze-dried powder were attributed to the retention of bioactive phytochemicals such as phenolics and flavonoids (quercetin, kaempferol, caffeic acid) known for their antimicrobial action. The findings demonstrate that freeze drying effectively preserves the structural characteristics and functional bioactivity of MPP while maintaining favorable in vitro biocompatibility and intestinal epithelial tolerance in Caco-2 cells.