Optimization of super dry hopping for medium and large-scale applications

The method of dry hopping consists of the addition of hops in the fermentation or maturation tank. This technique has gained popularity in recent years because of its capacity to impart the beer with appreciated intense hop aromas. Despite the fact that this technique is now widely used by the craft community, its performance is not yet fully controlled, and the current methods are characterized by several disadvantages (inconsistent extraction, extract and beer losses, operational complexity, etc.). Super dry hopping, which consists in miniaturization and externalization of the process in a smaller vessel, that is completely offline, either with beer or customized process water. This method is believed to be an innovative and flexible method capable of overcoming those challenges. This work aimed to develop a method of super dry hopping that is able to produce a beer that is similar, sensory-wise, to the same beer produced with a classical dry hopping method. With this in mind, the super dry hopping technique was tested and developed at three scales: laboratory scale, intermediate scale and pilot scale. The beers prepared at the different scale were subjected to physicochemical and sensory analyses. Thanks to the results obtained during this study, sensory profiles of super dry hopped beers were determined and potential gaps with the reference were highlighted and significant parameters were identified. The learnings gathered from the laboratory scale were crucial for the development of the experimental designs of the trials at intermediate and pilot scale and the selection of three worthwhile super dry hopped prototypes. At intermediate and pilot scale, the sensory analysis reported the super dry hopped beers as significantly different from the classical dry hopped reference. Super dry hopping was different in terms of the overall flavour impression as well as in the individual hop-related attributes, such as floral, citrusy and overall fruitiness. The physicochemical analyses reflected the gaps identified by the sensory analysis with lower concentrations of the markers quantified as well as decreased relative performances of dry hopping in the super dry hopped beers. The studied markers linalool, geraniol, 3S4MPol (3-sulfanyl-4-methylpentan-1-ol) and 4S4MPone (4-sulfanyl-4-methylpentan-2-one) didn’t exceed relative performances of dry hopping of 85%, 60%, 40% and 65%, respectively. Only 3SHol (3-sulfanylhexan-1-ol) was able to reach a relative performance of 100% (or higher) in three prototypes. However, it didn’t exceed 90% in the other three. The conversion rates of the thiol S-conjugates were, however, relatively high, although those results have to be carefully considered. Therefore, it is clear that super dry hopping is not capable, at this stage, to produce dry hopped beers that are similar to the dry hopped beers produced with the classical method. Nonetheless, several potential ways of improvement were identified. Indeed, further investigation of the sequential extractions as well as lower hop concentrations during the super dry hopping extraction, the addition of small fractions of hop pellets, in addition to the hop extracts, during super dry hopping and the use of exogenous enzymes are believed to be realistic solutions to close the gaps between super dry hopping and classical dry hopping.