Effect of full-scale brewing process on polyphenols in Italian all-malt and maize adjunct lager beers

This paper analyses, in a full-scale industrial process, the flavonoids, non-flavonoids, tannins and non-tannins in all malt worts and in maize adjunct worts and their fate during the main brewing steps. The effect on wort phenols of two different wort separation technologies, a mash filter (Meura 2001) and a lauter tun (Steinecker FVAS 26), were also investigated. The results obtained showed that total phenols are lower in maize-adjunct, than in all-malt worts (542 mg/L and 730 mg/L, respectively), and that non-tannins are the main phenolic components: 91% of the total in all-malt and 82% in maize-adjunct worts, respectively. The overall brewing process reduces the initial content of total phenols by 50%, and the highest reduction is on tannins and flavonoids. After the brewing process, total phenols in beer were 336.5 mg/L in all-malt and 280 mg/L in maize adjunct. In moderate drinkers they contribute to 10-20% of the total phenolic daily intake accounting for around 4-8% of the total antioxidant capacity of the diet. As regards the influence of lauter tun and mash filter on phenols, our results showed their great depletion when using lauter tun, and suggested that the brewing process may be adapted in order to overcome the high impact of lauter tun on phenols.