Abstract: To explore a new technique for replacing traditional heat processing, thermosonication (TS) (at 50 ℃ and 2.7 W/mL for 1, 2 and 3 min) and heat processing (at 60 ℃ for 15 min) of wheat beer were comparatively evaluated by examining their impacts on microbial populations, colloidal haze, flavor and foam stability during 84 days of storage. The results showed that the microbiological stability of TS-treated beer was comparable with that of heat-treated sample, and the development of both aerobic bacteria and lactic acid bacteria was inhibited during storage. The main parameters (ethanol content, original gravity, pH, bitterness and viscosity) were scarcely affected by either treatment compared to control samples. However, pasteurization increased the color value. Pasteurization resulted in an increase of phenethyl alcohol and ethyl acetate concentrations and a decrease of isoamyl acetate concentration in the beer compared to TS. These treatments did not affect the amounts of 4-vinylguaiacol and 4-vinylphenol in the beer. Meanwhile, TS-treated beer had higher colloidal haze and foam stability than pasteurized beer. Dynamic light scattering analysis showed that TS treatment resulted in a smaller and more uniform particle size, thus having a positive effect on the desired beer haze stability during storage.

Key words: wheat beer, thermosonication, quality properties, colloidal haze stability, dynamic light scattering