LILLE 2024

4-Mercapto-4-methyl-2-pentanone (4MMP) is a volatile thiol that contributes towards the pleasant blackcurrant aroma in hoppy beer styles. It is understood that the chemical and sensory profile of hoppy beers changes during storage. Some sensorial changes, i.e. the loss of fruity aroma, can occur shortly after packaging and have been linked to the decrease of 4MMP levels in beer. Therefore, a storage trial was performed in order to evaluate the chemical factors and reactions responsible for the decrease in 4MMP. In this trial, the role of temperature, oxygen, metals, polyphenols, protein thiols, sulphur dioxide and initial 4MMP concentration was evaluated in several beer styles, including a Lager, Pale Ale and New England IPA. In all matrices, copper sulphate addition strongly reduced 4MMP levels, whereas polyphenols were unable to prevent 4MMP reduction. Protein thiols were effective in slowing down 4MMP reductionoxidation, however this was dependent upon beer composition. The analysis of 4MMP disulfides in fresh and aged beer indicated that both 4MMP oxidation and potentially metal binding or reactions with polyphenols are responsible for reduced 4MMP levels in aged hoppy beer.

The sensory instability of beer is an undesirable phenomenon with a significant influence on sensory quality resulting in the stale flavour. Recent methods for evaluation of beer propensity for staling are based on storage of beer for a few months at e.g., 20 °C or a few days at e.g., 45 °C. Although the methods provide some information, their drawbacks make them useable for informative evaluation with difficulty. Hence, a project focused on the evaluation of the sensory stability of beer was launched by the authors. The project aims to develop a universal tool for quick evaluation of beer propensity for sensorial deterioration during storage (directly from fresh beer sample) by Fourier-transform infrared spectroscopy (FTIR) and convolutional neural network (CNN), useable for routine quality control of beer. The CNN was trained by data obtained from 163 beer brands (lagers, ales, and non-alcoholic beers) brewed by collaborative breweries (> 1000 samples) and naturally aged at 20 °C for 6 and 9 months. Resulted prediction performance for a test set expressed by the coefficient of determination was 0.83 and the prediction uncertainty was comparable with the experimental one. Beside

Beer consumers are seeking new beer flavors. To offer larger beer variety, the brewing industry uses different yeast strains such as Saccharomyces cerevisiae (Sc) and Saccharomyces pastorianus (Sp) among others. Using different yeasts requires ensuring accurate identification of each one and preventing any potential cross-contamination. So, having a rapid and reproducible method for this aim is crucial.
In Mahou-SanMiguel (MSM), different molecular methods and even MALDI-TOF have been tested. While these technologies differentiate Sc strains, they are not helpful for Sp strains due their similarity at genomic level. To solve this issue, the genome of 5 MSM Sp strains was sequenced by Illumina, to define specific qPCR primers for each one. Sp specie is a hybrid (Sc x Saccharomyces eubayanus -Se-). Hence, to detect areas of greater variability among strains, the reads were mapped against reference genomes of Sc and Se . Few SNPs were found to differentiate the strains. Sp, as a hybrid, may have unique chromosomal rearrangements useful to differentiate them. So, using SNPs and chromosomal rearrangements, a group of primers was developed to differentiate the most relevant MSM strains.

Beer gushing is an unprovoked over-foaming following the opening of a bottle. Primary gushing is highly dependent on barley growing and harvesting climatic conditions. This phenomenon can have economic and reputational consequences for breweries.
Current techniques, such as the Modified Carlsberg Test (MCT), provide information on a predictive gushing potential of malt with a high uncertainty and is time consuming. Thus, a rapid screening test for gushing potential on raw material could be of interest to the malting & brewing industries and for research purposes.
In prior research, we identified markers associated with beer gushing, aiming to create a method for their detection and quantification. To achieve this, we extracted proteins from industrial malt batches and employed a bioinformatic approach to pinpoint proteins relevant to the gushing phenomena. Afterwards, recombinant target proteins were used to produce antibodies to develop an ELISA test against these markers.
Currently, the ELISA test is available and is being implemented on a small scale with various raw materials as part of the method validation process.
The methodology and validation results will be presented.