SOME REASONS WHY HIGH GRAVITY BREWING HAS A NEGATIVE EFFECT ON HEAD RETENTION*

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Abstract
Our aim was to examine the effect of high gravity brewing on head retention with respect particularly to the effect of high gravity brewing on hydrophobic polypeptide levels. High gravity brewed beer had poorer head retention values when compared to a similarly brewed low gravity beer. Analysis of hydrophobic polypeptide levels in both high gravity wort (20° Plato) and low gravity wort (10° Plato) produced using a lauter tun, revealed that the high gravity wort contained 8% less hydrophobic polypeptide than the low gravity wort (undiluted basis). Analysis of hydrophobic polypeptides throughout the brewing process for these 10°P and 20°P brews demonstrated that the hydrophobic polypeptide content decreased, especially during the kettle boil and fermentation. Furthermore, the high gravity brewed beer suffered the greatest loss, leaving the final beer with approximately 40% less hydrophobic polypeptides than the low gravity beer. Brewing at 10°P and 20°P using a mash filter demonstrated that these filters can improve the head formation and stability of the resultant beers at sales gravity. However, the low gravity beer still produced a more stable foam (Rudin value 93 s) when compared to the high gravity beer (Rudin value 83 s). The mash filter slightly increased the hydrophobic polypeptide extraction. It is concluded that the mash filter produced higher hydrophobic polypeptide levels in the final beers, as well as having a positive effect on reducing the levels of foam negative compounds such as fatty acids in the wort, and therefore slightly improved head retention values.

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