Ultrasound-assisted thermal processing: Microbial safety and physicochemical attributes of Tejuino, a Mexican heritage fermented beverage

Introduction. Tejuino is an artisanal Mexican fermented corn beverage with limited shelf life, challenging industrial production. Research on microbial safety methods remains scarce despite their cultural importance. Objectives. This study aimed to evaluate the impact of Ultrasound-assisted thermal processing (USTP) on microbial safety and physicochemical properties on tejuino beverage. Materials and Methods. Commercial tejuino samples (200mL) underwent ultrasonic treatment at 0.5 kJ/mL at 20 °C, followed by thermal treatment at 45-65°C (USTP– USTP 65). Fresh, pasteurized (65°C/30 min), and ultrasound-treated samples served as controls. Analyses included microbiological [aerobic mesophilic bacteria (AMB), coliform bacteria (CB), molds and yeasts (MY), lactic acid bacteria (LAB)] and physicochemical parameters (pH, acidity, soluble solids, browning index, density, viscosity, conductivity, turbidity, color), as well as antioxidants [total soluble phenols (TSP), DPPH, ABTS, FRAP]. Results. AMB, CB, and MY counts decreased under USTP treatments while maintaining substantial LAB concentrations in a temperature-dependent response (USTP45–USTP65) compared to controls. All physicochemical properties except density were altered by USTP treatments in a temperature-dependent manner compared to fresh control. USTP45, USTP50, and USTP55 treatments showed similar TSP content and antioxidant activity by DPPH and ABTS compared to ultrasound-treated and fresh controls, while FRAP values decreased significantly in temperatures of >50°C. Conclusions. The ultrasound-assisted thermal processing can be a viable alternative for the industrial manufacturing of tejuino.