Why was the work done: To determine whether the susceptibility of lager to microbiological spoilage is determined by composition, microbiota or both. To assess beer spoilage by a consortium of yeasts and bacteria from draught beer rather than pure laboratory cultures. How was the work done: Four draught beer styles - cask ale and keg lager, ale, and stout – were sampled twice in five different public houses in four different locations. The beers were forced by static incubation at 30°C for four days. ‘Challenge testing’ with an inoculum of heterogeneous microorganisms from the forced samples was used to assess the spoilage of ten commercial lagers by the increase in turbidity at 660 nm. The same approach was used to evaluate the role of nutrients in beer spoilage by forcing with the addition of yeast extract or vitamins (thiamine and riboflavin). What are the main findings: The ten lagers varied in susceptibility to spoilage ranging three-fold from the least to most spoilable. Average spoilage of the beers was comparable for microorganisms from lager, keg ale and stout but ca. 50% greater with microorganisms from cask ale. The ranking of spoilage of the 10 lagers was similar for microbiota from cask ale, keg ale and stout but less so from lager. Spoilage was influenced by beer composition and was inversely related to beer pH and level of free amino nitrogen. The addition of yeast extract stimulated spoilage of the least spoilable lager but the addition of vitamins B1 and B2 had little or no effect. Spoilage was extensive at 30°C, measurable at 12°C but imperceptible at 2°C. Why is the work important: The oft-quoted statement that beer is ‘robust to microbiological spoilage’ is a fallacy. All ten lagers were spoilt by draught beer microorganisms, but some were more spoilable than others. It is suggested that spoilage may be reduced by lowering beer pH and curbing the availability of nutrients for microbial growth. Whilst (as would be expected) beer storage at 2°C suppresses microbial growth, storage at 12°C (as practiced in UK public house cellars) allows spoilage microorganisms to grow in beer. Although the threat of microbial spoilage in the brewing process is managed by good manufacturing practices, draught beer is vulnerable and requires more focus and commitment to hygienic practices to assure quality.

In 2022, the Journal of the Institute of Brewing published two reviews and 14 papers. Front and centre of the process is peer review. This is a key process in scientific publication. It inevitably takes much time but without doubt results in a significantly better manuscript to the benefit of the authors, the Journal and its readers. I would like to fulsomely thank the 43 busy reviewers who freely gave their time and expertise to review manuscripts for the Journal in 2022. Many will have reviewed the manuscript on submission and after revision. Further, some reviewers were kind enough to review two or more manuscripts. The contribution of all 43 reviewers to the Journal is hugely appreciated.

AIMS:To determine whether the culture-dependent spoilage microflora found in draught beer are influenced by beer style.METHODS AND RESULTS:Four beer styles-lager, ale, stout and cask ale - were sampled twice from five different public houses (accounts) in four different locations. The microbiological quality of the dispensed beers was determined by a culture-dependent method ('forcing'), measuring the increase in turbidity after incubation at 30°C. The quality of draught beer varied from 'excellent' to 'poor' with cask beer samples having a higher Quality Index (90%) with keg ale the lowest (67.5%). With PCR amplified DNA (ITS1, ITS4, 16S rRNA primers) and blast identification of microflora, 386 colonies from agar plates were identified with 28 different micro-organisms from five genera of yeast and six of bacteria. Seven micro-organisms were found in all beer styles with Brettanomyces bruxellensis, B. anomalus and Acetobacter fabarum representing 53% of the identified micro-organisms. A subsequent, limited study using PALL multiplex PCR GeneDisc technology on forced samples (without selection on plates) suggests that draught beer microflora is qualitatively broader. It is noteworthy that the microflora of spoilt draught beer resembles that involved in the production of Belgian Lambic sour beers.CONCLUSIONS:Draught beer was of variable quality. Culture-dependent analysis suggests that species of Brettanomyces and Acetobacter are core microflora with some micro-organisms being associated with beer style.SIGNIFICANCE AND IMPACT OF THE STUDY:The microbiological quality of draught beer is important both commercially and to the consumer. Here, we report the core and diverse microflora found in different styles of draught beer using culture-dependent methods.

The spoilage of six alcohol-free (AFB, ≤ 0.05% ABV) and two low alcohol beers (LAB, ≤ 1.2% ABV) was assessed by challenge testing with microflora from draught beer. Spoilage of AFB and LABs was greater (2-5 x) than two ‘control’ premium lager beers (4.5% ABV). Measurement of spoilage by challenge testing was reproducible irrespective of the source of draught beer microflora (public house, date, or beer style). Spoilage was correlated with the level of ‘fermentables’ (glucose + fructose + maltose) in the product but was also dependent on the availability of micronutrients. The addition of ethanol (2-8% ABV) to three AFBs and a LAB resulted only in a modest inhibition of spoilage (collectively 24% at 8% ABV) and, it is suggested, that the complexity of the product composition provides protection. Given the vulnerability of AFBs and LABs to spoilage and susceptibility to microorganisms that are usually supressed by ethanol, it is strongly recommended that low or alcohol-free beer styles are not offered to consumers in the on-trade by conventional long line dispense systems. It is suggested that AFB and LABs in a draught format require innovative, hygienically designed stand-alone dispense systems that remove or significantly minimise the risk of microbiological contamination, growth and associated product spoilage. © 2021 The Institute of Brewing & Distilling

Draught beer quality is assured by the management of microbial biofilm in dispense lines through regular and effective line cleaning with alkaline detergent. Here, a method is described which enables biofilm formation, growth and removal to be assessed in 96 well polyvinyl chloride microplates. Draught beer (and cider) microflora formed reproducible biofilms in their ‘parent’ beer after incubation at 15°C for seven days. Biofilm formation by four draught beer styles – keg lager, ale, stout and cask ale - was assessed and was enhanced by periodic replenishment with fresh beer. The rate of biofilm formation by microflora from keg beers decreased with increasing temperature whereas with cask ale it increased. Oxygen enhanced biofilm formation with microflora from cask ale but not keg. Simulation of line cleaning in microplates with a proprietary alkaline solution failed to kill all microflora and the microorganisms regrew in all four beer styles. Further, the line cleaning process was increasingly ineffective with older biofilms. It is suggested that the method reported here will help focus attention on the efficacy of line cleaning, in particular, the role of mechanical action, which contributes little to the standard manual line cleaning process in the UK. This and other investigations will hopefully contribute to the ultimate intention of improving and assuring draught beer quality.

The quality of draught beer in 57 on-trade licensed premises in 10 locations in the UK Midlands was assessed using a forcing test. Of 149 samples of standard lager ('SL', abv <= 4.2%), 44% were in the 'excellent' quality band compared with 16% of 88 samples of keg ale ('KA', abv <= 4.2%). Of the total of 237 samples, >90% were represented by two lager and two ale national brands. There were differences in the quality index (QI) between the brands, with lager SL3 having a QI of 84% compared with 72% for lager SL6, 71% for ale KA5 and 68% for ale KA1. The susceptibility of the four brands to spoilage was assessed using a challenge test with microorganisms taken from forced draught beer samples of the brands. Ale KA5 (challenge test QI = 87.5%) was the most resistant to spoilage followed by lager SL3 (81.3%), lager SL6 (75%) and ale KA1 (62.5%). Keg beers in accounts with a national cask beer quality accreditation had the same QI as those without accreditation. Analysis of price vs quality showed that the most expensive price band had the lowest quality. Draught beer quality declined as the number of dispense taps increased across the bar. It was also noted that dispense into branded half-pint glasses had variable take-up, with lager SL3 served in the correct branded glassware on 71% of occasions but only on 5% of occasions for lager SL6. None of the keg ales were served in correctly branded glassware. (C) 2018 The Institute of Brewing & Distilling

The quality of draught beer is important to consumers but can be inconsistent, ranging from excellent through to unacceptable. The few, dated studies of draught beer quality have focused on the number of microorganisms that are present in the product. Work reported here suggests that this approach has its limitations and fails to relate to beer quality post-dispense. An alternative approach using the long-established forcing' method provides a better but still retrospective assessment of draught beer quality. Samples post dispense are forced' by static incubation at 30 degrees C for four days and beer quality is ranked by the measurement of absorbance at 660 nm. The increase in absorbance reflects the growth of beer spoilage microorganisms present in the beer at dispense. Four quality bands are proposed, where quality is described as excellent (absorbance increase of <0.3), acceptable (0.3-0.6), poor (0.6-0.9) and unacceptable (>0.9). The method is straightforward, requires no special skills and enables, for the first time, the robust quantification of draught beer quality. It is anticipated that the method will have widespread application in the measurement and improvement of the quality of draught beer. Copyright (c) 2017 The Institute of Brewing & Distilling

The bottom line in brewery fermentation is that consistency is paramount. Whatever the scale of the operation, excellent yeast quality is a fundamental process requirement to ensure good and sustainable beer quality. The recycling of yeast across numerous fermentations adds complexity and biological stress. It is recommended that this be compensated by application of best practice in yeast supply/propagation, pitching, fermentation and storage. Craft brewers operating at a small scale and without recycling should be conscious of best practice for the rehydration of active dried yeast.

Draught beer quality can be compromised by the growth of spoilage microorganisms. Whilst best practice for assuring dispense hygiene is broadly recognized, it is not always fully or regularly implemented. In some markets, tap nozzles are removed and stored overnight at room temperature in carbonated (soda) water. The next morning they are returned (sometimes after rinsing) to the dispense tap. The effectiveness of this approach is compared with soaking in diluted line-cleaning solution (UK best practice) or a solution containing hypochlorous acid (commercial sanitizing tablets). Two novel approaches - ozonated water and use of ultrasonics - were also evaluated. Bioluminescence analysis of microbial attachment to the inner surfaces of nozzles showed that soaking in carbonated water resulted in gross contamination. Sanitizing tablets achieved commercial sterility' and a 4-log reduction in bioluminescence compared with carbonated water. The efficacy of hypochlorous acid was confirmed by incubating cleaned nozzles in fresh beer without any increase in turbidity. Diluted line-cleaning solution was less effective and achieved a 2-log reduction. Ultrasonics reduced microbial attachment but effectiveness was aligned to increasing process time. Soaking in ozonated water was without antimicrobial impact. This work has shown carbonated water to be ineffective in cleaning microbiologically contaminated nozzles. This is a concern as these microorganisms derive from the dispense line, the environment and likely human interaction. To minimize the risks of transfer to dispensed product or back-contaminating the dispense line, soaking draught beer nozzles in an effective sanitizing solution is strongly recommended. Copyright (c) 2016 The Institute of Brewing & Distilling

The draught beer category is in long-term decline. Product quality is one of a number of factors that have contributed to consumers switching from the on- to off-trade/premise. This reflects increasing dispense system complexity and poor hygienic practices that together result in poor product microbiology. Routes to improve system hygiene and product quality require sustainable implementation of recognised best practice. Whilst doing the right things right would provide a ready improvement to product quality, there are also a number of diverse innovations that individually and collectively could make a positive difference to assure draught beer microbiology and consequent beer quality.

In the theatre of brewing, yeast is viewed, quite inappropriately, as a “supporting actor.” But unlike the more commercial leading actors, water, malt and hops, yeast appears not once but in many successive productions. Further, with fermentation being the longest chunk of the process, yeast is on stage longer. Finally and critically, as an agent of change, yeast facilitates the most dramatic event in the whole production—transformation of wort to beer. Given this impressive history, it is a surprise that yeast is not lauded and celebrated as the real star of the production of beer. This thinking is the foundation of this chapter and the chapter focuses on the principles and best practices behind in-brewery propagation of yeast together with emerging “work-arounds,” such as the advent of active dried yeast.

Studies of yeast obtained postfermentation have largely considered individual cells within the crop to be phenotypically and genotypically similar. However, previous studies have indicated that environmental conditions within the cone of a cylindroconical vessel are variable, suggesting that physiological and potentially genetic heterogeneity may occur. Two 2,000-hL fermentation vessels, pitched in parallel with a lager strain, were cropped using two regimens and yeast fractions obtained at 500-kg intervals. Each yeast fraction was analyzed for factors impacting fermentation performance. In addition, characteristics of the barm beer were investigated. Analysis of yeast postfermentation indicated extensive heterogeneity within the crop, in terms of physiological condition, flocculation potential, cell size, and replicative age. In addition, environmental conditions within the cone were also observed to vary substantially. Gradients in terms of temperature, pH, gravity, and ethanol were all detected within the cone. Although cropping regimens can differ, it is proposed that variation in yeast quality throughout the cone may facilitate selection during cropping. Successively cropping and pitching with a specific portion of the cone may lead to the accumulation of a population comprising cells with inappropriate fermentative characteristics, potentially leading to fermentation inconsistency.