Impact of thermal processing on amino acid composition, physicochemical properties, and bioactive compounds of watermeal (Wolffia globosa) extract

• Thermal processing improved protein solubility of watermeal extract (WME). • Boiling and autoclaving enhanced the amino acid content of WME. • Bitterness-related amino acids increased most after autoclaving. • Thermal processing enhanced the release of certain phenolics and flavonoids. • Gentisic acid, catechin, and apigenin were maximized after boiling. Watermeal ( Wolffia globosa ) is a nutrient-dense aquatic plant receiving increasing attention as a sustainable plant-based protein source due to its protein content and bioactive compounds. This study investigated the effects of two thermal processes, namely boiling and autoclaving, on the amino acid composition, physicochemical properties, bioactive compound and antioxidant activities of a watermeal extract (WME). Boiling markedly increased essential amino acids (45.4 to 79.9 mg/100 mL), particularly valine, methionine, and phenylalanine. Sweet-related amino acids remained predominant, although bitterness-associated amino acids also increased slightly after heating. Both processes lowered the pH and lightness but enhanced total soluble solids and protein content, with boiled samples showing the highest protein content (176 mg/100 mL), followed by autoclaved and raw samples. The total phenolic content nearly tripled after boiling, increasing from 236 to 635 µg GAE/mL (2.7-fold), while total flavonoid content increased by 2.5-fold. DPPH radical scavenging activity increased by 7.5-fold in boiled samples (104 to 775 µg AA/mL) and by 7.1-fold in autoclaved samples, accompanied by a corresponding rise in reducing power, as indicated by FRAP values (4600 to 5700 µg FeSO₄/mL). HPLC analysis confirmed an increased release of gentisic acid, catechin, and apigenin after boiling. These results suggest that thermally processed WME, particularly when processed by boiling, can serve as a promising functional ingredient for plant-based beverages, protein-fortified foods, and nutraceutical formulations, while providing a basis for the further development of sustainable protein ingredients through process optimization and product formulation studies.