Pulsed Electric Field continuous pasteurization of different types of beers

- Saccharomyces cerevisiae ascospores were inactivated by PEF in nine beers.
- Thermal assisted PEF (≤53 °C) caused further inactivation of S. cerevisiae spores.
- The higher the alcohol content, the higher the PEF yeast inactivation in beer.

Thermal pasteurization of bottled beer is used to extend its shelf life. However, the thermal process negatively affects the beer sensory. In this research, beer was processed using Pulsed Electric Fields (PEF), a non-thermal continuous preservation technology that has the potential to be implemented at a commercial scale by the brewing industry. The main goal of this work was to investigate the feasibility of PEF for yeast inactivation and its impact on beer sensory.First, the effect of a PEF process (temperature below 43 °C, 45 kV/cm electrical field intensity, 46 pulses, 70 μs) on Saccharomyces cerevisiae ascospores inactivation in nine different beers comprising ale, lager, dark, low alcohol, and no alcohol, was investigated. Log reductions of 0.2 and 2.2 were registered for 0 and 7% alc/vol beers, respectively, which indicated that the alcohol content is the major beer constituent driving the microbial inactivation. Then, 0, 4, and 7% alc/vol beers containing S. cerevisiae ascospores were submitted to PEF combined with thermal processing up to 53 °C. An increase in the PEF treatment temperature from 43 to 53 °C caused at least an additional 0.7, 2.1 and 1.8 log reductions in the yeast spore population for 0, 4, and 7% alc/vol beers, respectively. Results of another experiment carried out with 4 and 7% alc/vol beers, showed the huge advantage of using PEF compared with thermal processing. Additionally, lightstruck attribute sensory tests revealed six (aroma) and three (flavour) PEF beers did not develop the lightstruck character, being acceptable in terms of sensory. The results of this study can be helpful for designing appropriate PEF conditions to pasteurize beers with different alcohol contents.