Ohmic heating-assisted pasteurization of beer: Effects on quality, antioxidant, and yeast growth

The study compared ohmic heating (OH) and conventional heating (CH) pasteurization of non‑carbonated beer to evaluate their effects on physicochemical properties, antioxidant capacity, polyphenol profile, microbiological quality, and yeast microstructure. Beer samples were pasteurized in a temperature-controlled bath at 60 °C (CH) and subjected to an electric field of 13 V/cm (OH) for 30 min. Quality parameters included color, pH, total polyphenol content (TPC), antioxidant capacity using the DPPH assay, individual phenolic compounds by HPLC-DAD, mold and yeast counts, and scanning electron microscopy (SEM). The results showed that ohmic heating preserved higher levels of bioactive compounds than conventional heating. After 10 min, ohmic heating maintained a higher total phosphate concentration (724.80 mg GAE/L) and antioxidant capacity (165.49 mg TE/L) than conventional heating (660.30 mg GAE/L and 123.46 mg TE/L, respectively). However, the ohmic treatment produced significant color changes, with ΔE* values increasing to 12.54 after 30 min, indicating marked darkening, while the CH treatment caused only minor variations (ΔE* < 1.5). pH values remained stable across all treatments. Microbiological analysis showed no detectable yeast growth after 20 min with ohmic heating, while CH required 30 min for complete inactivation. Scanning electron microscopy (SEM) analysis confirmed greater structural damage in yeast cells treated with ohmic heating compared to those treated with CH. Overall, OH treatment showed greater efficiency in microbial inactivation and better preservation of functional compounds, although further optimization of OH is still required to reduce undesirable color alterations in beer.