Dry hopping is a brewing technique where hops or hop products are added to the process during beer fermentation or maturation. This technique is used by brewers to impart hop characteristics to the beer, which in turn changes the aroma and flavour profile. The dry hopping process differs significantly from traditional kettle hopping during wort boiling and has gained substantial interest in recent years. However, due to its novelty, certain aspects of dry hopping remain unexplored and require further studies. In this study, we conducted dry hopping experiments at the laboratory scale using lager beer. We investigated the influence of various factors such as the duration of the process, different hop varieties, temperature, and agitation on the extraction of hop components into the beer. The process was conducted under varying conditions of temperature and agitation – dynamic (with mixing) and static (without mixing). Specifically, we focused on understanding the extraction of bittering compounds during dry hopping, which include α-acids, iso-α-acids, and polyphenols. Our results indicate that the concentration of α-acids and polyphenols increases during dry hopping, while the concentration of iso-α-acids decreases. We found that the extraction of hop components depends on factors like hop variety, temperature, agitation intensity, as well as the initial beer characteristics such as pH and alcohol content. Additionally, we evaluated the dry-hopped beers using spectrophotometric analysis to determine their bitterness, quantified as International Bitterness Units (IBU). This provided insights into the extraction of less studied bittering hop compounds. Our study raises questions about the suitability of this analytical method for assessing bitterness in dry-hopped beers and highlights the need for improved analytical techniques to accurately quantify the complex changes in beer composition during the dry hopping process. These findings contribute to a partial understanding of how hop components interact with beer matrices during cold hopping, offering valuable information for brewers aiming to optimize the production of dry-hopped beer and its bitterness profiles.
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