Enhancing tea brewing with ultrasound: effects of temperature on antioxidant and antibacterial activities

Abstract This study investigated the effects of ultrasound (US)-assisted extraction on the antioxidant properties and antimicrobial activities of black, oolong, green, and matcha teas. Tea infusions were prepared using US treatment at two temperatures (45 °C and 90 °C) and compared with conventionally brewed samples. Antioxidant capacity was evaluated via cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, along with total phenolic content (TPC) and total flavonoid content (TFC). Results showed that antioxidant activity and bioactive compound levels varied significantly with tea type and brewing temperature. Matcha brewed at higher temperature consistently exhibited the strongest antioxidant responses across the assays, whereas black tea showed comparatively lower activity. Black teas showed the lowest activity across all parameters. Antibacterial evaluations revealed that US-assisted teas, particularly high-temperature matcha and green tea infusions, demonstrated pronounced inhibitory effects against E. coli , with matcha also exhibiting notable activity against S. typhimurium . US-assisted brewing, especially at high temperatures, enhanced the extraction of bioactive compounds and improved the antimicrobial efficacy of tea infusions. Graphical abstract