Comparative analysis of physicochemical properties and antioxidant activities of kale (Brassica oleracea var. acephala) under organic and conventional cultivation systems

This study evaluated the physicochemical properties, bioactive compounds, and antioxidant activities of kale cultivated under conventional and organic systems. Moisture content showed little difference between groups, while ash values varied more widely in organic kale. Crude protein was higher in organic kale, averaging about 0.55% compared to 0.39% in conventional samples, and crude fat was also slightly greater at up to 2.36% in organic kale versus 2.07% in conventional kale. Total polyphenol and flavonoid contents were greater in organic kale, reaching over 312.53 μg GAE/g and 75.40 μg QE/g, while the lowest values in conventional kale were around 238.56 μg GAE/g and 18.07 μg QE/g. The highest β-carotene concentration was observed in organic kale at more than 31.02 μg/g, exceeding the lowest level in conventional kale of about 20.71 μg/g. Glucosinolate analysis revealed increased levels in organic samples, particularly gluconapin and 4-methoxyglucobrassicin. Antioxidant assays demonstrated that organic kale exhibited superior activity, with DPPH radical scavenging close to 62.01-64.59%, ABTS scavenging above 75.00%, and reducing power values approaching 0.85-0.95. These findings indicate that organic cultivation enhances the accumulation of bioactive compounds and improves antioxidant capacity, supporting the nutritional and functional advantages of organically grown kale.