Effects of conventional and high-pressure boiling on phenolic and flavonoid profiles, antioxidant activity, and in vitro gut microbiota modulation of Thai Kaeng Khae curry soup

ABSTRACT Increasing interest in vegetable-rich diets has highlighted Kaeng Khae, a traditional Northern Thai curry soup composed of seven indigenous vegetables. This study compared the effects of conventional boiling (NBKK) and high-pressure boiling (HBKK) on phenolic and flavonoid profiles, antioxidant activity, and in vitro gut microbiota modulation of Kaeng Khae. High-pressure boiling significantly enhanced the retention of total phenolic content (TPC) and total flavonoid content (TFC) compared with conventional boiling. Phenolic and flavonoid profiling revealed chlorogenic acid and naringenin as the predominant compounds in both treatments. HBKK exhibited greater in vitro antioxidant activity and improved bioaccessibility of key phytochemicals following simulated gastrointestinal digestion. In vitro human fecal fermentation analysis demonstrated that HBKK modulated gut microbiota composition at the phylum level and promoted higher production of short-chain fatty acids (SCFAs), particularly acetate and butyrate, compared with NBKK. These findings indicate that the boiling method influences phytochemical stability and subsequent microbial fermentation outcomes. Overall, high-pressure boiling improved the retention of bioactive compounds and enhanced microbiota-related fermentation responses in Kaeng Khae. This study provides evidence that processing conditions can modulate the functional properties of traditional vegetable-based foods.