Air-Frying Improves the Bioactive Compounds of Thermally Processed <i>Brassica oleracea</i> Vegetables

Brassica oleracea vegetables, including cabbage, kale, Brussels sprouts, and broccoli sprouts, are renowned for their rich phenolic contents and bioactive compounds. This study investigated the impact of thermal processing on key bioactives, including phenolic acids, flavonoids, glucosinolates (such as sulforaphane), fatty acids, and phytosterols. Additionally, we evaluated bioactivities such as angiotensin-converting enzyme (ACE) inhibitory activity, lipid peroxidation activity, and α-amylase inhibitory activity. Among the thermal processing methods tested, air-frying significantly enhanced the bioactive composition of Brassica vegetables. Notably, phenolic acids, such as chlorogenic and caffeic acids, were significantly increased (p < 0.05) with air-frying. Air-fried kale and broccoli sprouts exhibited superior α-amylase and ACE inhibitory activities (p < 0.05), indicating their potential antidiabetic and antihypertensive benefits. These findings emphasize the effectiveness of air-frying in optimizing the health-promoting properties of Brassica vegetables, offering a sustainable approach to improving their nutritional profiles. This study underscores the potential of air-fried Brassica species in the development of functional food products with enhanced bioactive properties.