Comparative Analysis of Biochemical and Physiological Parameters: Unraveling the Influence of Harvest Timing in Two Kale Cultivars (<i>Brassica oleracea</i> L. var. Sabellica)

This study aimed to evaluate which kale (Brasicca oleracea L. var. sabellica) cultivar and sampling period are the most suitable for crop yield and accumulation of bioactive compounds. Two commercial kale cultivars, “Curly Kale” and “Black Magic”, were grown under field conditions, and their biochemical and physiological parameters were assessed over three sampling periods. Black Magic presented higher biomass production and accumulation of mineral nutrients in the early stages of the crop, and greater amino acid and carotenoid accumulation. Meanwhile, Curly Kale showed higher biomass toward the end of the crop, supported by its better phytohormonal profile, its greater accumulation of phenolic compounds and ascorbate, and its higher values of antioxidant tests. Furthermore, sampling in the intermediate phases would be more appropriate to promote antioxidant accumulation, whereas sampling toward the end of the crop is more appropriate for mineral nutrient accumulation. Overall, Curly Kale emerged as a superior cultivar in terms of growth, accumulation of bioactive compounds, and antioxidant capacity, suggesting its potential as a functional food source.