The Effect of Steam Blanching and Drying Method on Nutrients, Phytochemicals and Antioxidant Activity of Moringa ( Moringa oleifera L.) Leaves

The antioxidant activity of plant materials is affected by post-harvest treatments. The present study was undertaken to evaluate the effects of steam blanching and two (solar and electric) drying methods on physicochemical composition, antioxidant activity (AOA) and rehydration properties of Moringa oleifera leaves. Fresh and blanched leaves of M. oleifera were dried by indirect solar-drying (≈35 ± 3°C, 12 h) and hot air electric drying (50°C, 5 h), and milled into flour (particle size ≤ 500 µm). Fresh, blanched and dried leaves were analyzed for their nutrient and phytochemical contents, antioxidant activity (Total Reducing Power (TRP) and 2,2-diphenyl-2-picryl hydrazyl (DPPH) scavenging activity) as well as rehydration properties (water absorption capacity (WAC) and water solubility index (WSI). Macronutrients content of M. oleifera leaves were unaffected by blanching and drying. Irrespective of drying method, drying had a significant negative effect (p < 0.05) on phytochemical contents, TRP and DPPH scavenging activity of M. oleifera leaves. Blanching prior to drying, however, dimmed the negative effect of the latter. Blanched leaves exhibited higher carotenoids content, TRP and WAC compared to unblanched leaves; whereas blanching caused a decrease in DPPH scavenging activity, vitamin C and WSI. This study highlights that fresh and blanched Moringa oleifera leaves are more suiTableas a source of dietary antioxidants than dry leaves.