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The paper reviews a career of more than forty years researching topics in malting and brewing science. Some themes attracted particularly close attention, namely the endosperm cell walls of barley, dimethyl sulphide, flavour stability, foam and the impact of beer on health. However, the scope has been far broader than that. The underlying imperative was to pursue research that was close to application and always focussed on a specific need in the processes involved in the production of beer. © 2020 The Institute of Brewing & Distilling.

NMR-focused metabolomic analysis has been employed to ascertain the extent to which a diversity of non-volatile substances change in level during maturation and storage on a pilot and commercial scale. No substantive changes were observed, leading to the conclusion that, once materials such as vicinal diketones and acetaldehyde have been dealt with, there is no merit in the prolonged storage of beer. © 2019 The Institute of Brewing & Distilling.

Flowers of the hop plant provide both bitterness and "hoppy" flavor to beer. Hops are, however, both a water and energy intensive crop and vary considerably in essential oil content, making it challenging to achieve a consistent hoppy taste in beer. Here, we report that brewer's yeast can be engineered to biosynthesize aromatic monoterpene molecules that impart hoppy flavor to beer by incorporating recombinant DNA derived from yeast, mint, and basil. Whereas metabolic engineering of biosynthetic pathways is commonly enlisted to maximize product titers, tuning expression of pathway enzymes to affect target production levels of multiple commercially important metabolites without major collateral metabolic changes represents a unique challenge. By applying state-of-the-art engineering techniques and a framework to guide iterative improvement, strains are generated with target performance characteristics. Beers produced using these strains are perceived as hoppier than traditionally hopped beers by a sensory panel in a double-blind tasting.

Dimethyl sulphoxide (DMSO) reductase is present in all brewing yeast strains tested, but is more readily detectable using activity stains on polyacrylamide gels than through direct spectrophotometric assay of crude extracts. The enzyme is detectable at higher activities in yeast cultivated at lower temperatures and this is because of increased expression of the primary gene that codes for the enzyme in yeast, MXR1. DMSO somewhat increases enzyme expression, notably in lager yeast by up to 70%, whereas methionine suppresses it. Both ale and lager strains produce enzymes of ~100,000 in molecular weight, but ion exchange chromatography divides the activity for both ale and lager yeasts into two fractions with distinct properties (heat tolerance, pH optimum, kinetic parameters). Copyright © 2017 The Institute of Brewing & Distilling.

Beer contains low-molecular-weight β-linked oligosaccharides that originate from the degradation of β-glucan in the barley cell wall during malting and mashing. Over 90% of these oligosaccharides contain three or four glucosyl units. They remain intact through a static oral, gastric and small intestinal in vitro human digestive system model, indicating that they should be available to beneficial organisms known to be present in the human large intestine. Several intestine-associated Lactobacillus strains were shown to be capable of growth on these β-linked oligosaccharides, thereby leading us to tentatively propose that these compounds may represent prebiotics. Copyright © 2017 The Institute of Brewing & Distilling.

Like iron and copper, manganese promotes the staling of beer, by converting ground state oxygen to reactive oxygen species. Manganese was detected in beers at levels that are likely to impact the aging of beer. Manganese originates in the grist materials but is present at even higher levels in hops. Although there is substantially more iron in those hops than manganese, the delivery into beer of these ions is much greater for manganese. Leaching of manganese into beer is much higher than in the equivalent quantity of deionized water. This study suggests that further study is warranted into the adverse impact of dry hopping on the flavor stability of beers.

The flavour of beer is complex, based upon changes at the molecular level in the key raw materials, notably grain, hops and yeast, as well as during the process stages that comprise malting and brewing. As analytical techniques evolve in their sophistication and sensitivity, there are opportunities to delve ever more deeply into the fate of small molecules in brewing. To this end, 1H nuclear magnetic resonance (NMR) metabolomics was used to follow the progression of 76 metabolites in four different late or dry hopped beers (brewed in triplicate) at five time points throughout the brewing process. The majority of the metabolites identified, including sugars, amino acids and nucleotides, significantly decreased in concentration from the start of the boil to post-secondary fermentation, whereas energy-related and fatty acid associated metabolites significantly increased in concentration as wort nutrients were consumed by the yeast. Adenine was significantly higher in the dry hopped brews than in the late hopped brews after both primary (p=2.1×10-6) and secondary (p=2.7×10-9) fermentation, while 2′-deoxyadenosine (after primary, p=1.1×10-2, after secondary, p=3.2×10-5) and adenosine (after primary, p=2.6×10-8; after secondary, p=3.1×10-7)were significantly lower in the dry hopped beers at these time points. These results give molecular insight into the brewing process and the differential effects of hopping methods on yeast purine metabolism.

Although there are product-to-product differences, the majority of the crystal and caramel malts tested have been shown to have a net destabilizing impact on foam. A foaming test using a model beer has been developed to quantify the magnitude of this inhibitory effect. Lipid analysis using thin-layer chromatography reveals that there are elevated levels of triglycerides in problematic malts. There also appear to be oxidized lipids in the specialty malts, probably produced in the heating stage of malt production with higher levels in more intensely heated products. However some specialty malts, such as black malt, while containing such foam-negative entities, do display superior foaming properties, probably because they develop even more powerful foam-positive components in the severe heating events. © 2014 The Institute of Brewing & Distilling.

Dimethyl sulfide (DMS) is a substantial contributor to the aroma of many lager-style beers. Opinion varies on its desirability. It can be derived in beer from two sources: the thermal decomposition of S-methylmethionine (SMM) produced in the embryo of barley during germination, or the reduction of dimethyl sulfoxide (DMSO, derived from the breakdown of SMM during the curing of malt) by yeast. The enzyme that effects DMSO reduction is a reductase whose primary function is the reduction of methionine sulfoxide and which competes for reducing power with several other cellular systems. Control of DMS production from SMM is achieved by specifying precursor levels in malt, by attending to the vigor and duration of the boil, and by controlling the length of the whirlpool stand. Control of DMS production from yeast is achieved by specifying yeast strain, wort gravity, free amino nitrogen and pH, the type of fermenter (ergo the extent of volatilization), and the fermentation temperature.

Why was the work done: Gushing caused by hydrophobin originating from field fungal contamination of grain remains a significant problem in certain regions. We sought to explore whether the use of added proteinase enzymes could overcome the problem and allow the use of problematic grain. How was the work done: Four commercial proteinases were studied for their ability to digest hydrophobin and remove its foaming potential. One of those enzymes was then explored for its utility as an addition to mashing with a view to lowering the gushing potential of the ensuing beer. What are the main findings: The four enzyme preparations (Smizyme LP-G, Thermoase PC, Bromelain and Papain) were all capable of digesting hydrophobin. Of these, papain was chosen to assess whether the use of such an enzyme in mashing could ameliorate the gushing potential in finished beers. It was demonstrated that this can be achieved and without apparent detriment to the foaming potential of those beers. Why is the work important: It is now possible for brewers to consider an alternative approach to rectifying gushing risks if they are confronted with problematic grain. It must be stressed that this technique will not address the other main risk from infections of this type, namely the production of mycotoxins. Even in a context where gushing is not a problem, this work has indicated that there should be little concern with addition of papain at the mashing stage from a perspective of decreasing the foaming performance of beer. [ABSTRACT FROM AUTHOR]

Ascorbic acid oxidase (AAO) develops in the embryo tissues of barley during steeping and initial stages of germination. Two AAO enzymes have been identified. One of them is of remarkably low molecular weight (

American coolship ale (ACA) is a type of spontaneously fermented beer that employs production methods similar to traditional Belgian lambic. In spite of its growing popularity in the American craft-brewing sector, the fermentation microbiology of ACA has not been previously described, and thus the interface between production methodology and microbial community structure is unexplored. Using terminal restriction fragment length polymorphism (TRFLP), barcoded amplicon sequencing (BAS), quantitative PCR (qPCR) and culture-dependent analysis, ACA fermentations were shown to follow a consistent fermentation progression, initially dominated by Enterobacteriaceae and a range of oxidative yeasts in the first month, then ceding to Saccharomyces spp. and Lactobacillales for the following year. After one year of fermentation, Brettanomyces bruxellensis was the dominant yeast population (occasionally accompanied by minor populations of Candida spp., Pichia spp., and other yeasts) and Lactobacillales remained dominant, though various aerobic bacteria became more prevalent. This work demonstrates that ACA exhibits a conserved core microbial succession in absence of inoculation, supporting the role of a resident brewhouse microbiota. These findings establish this core microbial profile of spontaneous beer fermentations as a target for production control points and quality standards for these beers.

Approaches to brewing are suffused with dogmatic insistence that certain techniques are unequivocally linked to the delivery of quality products. Amongst these belief sets is the perseverance with prolonged maturation (or 'conditioning') times post-fermentation. Historically the justification for these lagering techniques was to allow settling of solids, carbonation, flavour maturation and removal of chill haze entities. As science and technology have advanced it is unequivocally the case that solids and chill haze precursors can be dealt with in short order and without the need for lengthy treatments. Equally it is perfectly possible to deliver specified levels of carbonation without the need for all the carbon dioxide to be introduced via yeast action. However, there remain many who feel that the nature of carbonation differs depending on which approach is taken. Herein lies one of the research areas that the author proposes. The perception of carbonation is not primarily due to bubble release on the palate, but rather is through the detection of carbonic acid. Is there a difference in the availability of this form of the gas depending on the mode of carbonation and to what extent does the adsorption of the carbonic acid on polypeptides in the beer have a role to play? In terms of flavour, the advocates for lagering insist that there needs to be a handling of vicinal diketones, acetaldehyde, and hydrogen sulphide. However, all of these can be controlled through attention to primary fermentation. Then, the proponents for maturation insist that there is a desirable release of non-volatile materials into beer, which substances supposedly benefit the balance and mouthfeel of the lager. These include amino acids and nucleotides. It seems to this author however that the likeliest explanation for the greatly increased levels of these materials and of pH is autolysis of yeast. This, together with the disadvantageous impact of increased free amino nitrogen and higher pH on aspects such as biological stability, flavour stability and foam, should convince any brewer that there is a sound argument for avoiding the prolonged contact of beer with yeast. Indeed, a metabolomic approach to studying changes in non-volatile substances under conditions where there is little or no autolysis, revealed no detectable changes in any entity. The author is open to being convinced that there are yet unidentified materials that are developed (whether through the action of viable yeast or by yeast autolysis) as beer is stored, substances which can be proven through sound organoleptic investigation to benefit the flavour of beer. Perhaps the Japanese term, kokumi, is what we are looking for here: 'rich taste'. This is believed to be afforded by γ-glutamyl peptides and, inter alia, these are to be found in yeast extracts. Herein lies the second experimental approach that the author recommends for pursuit. [ABSTRACT FROM AUTHOR]