Journal of The Institute of Brewing最新文献

Flavour stability, or instability, relates to the rate of flavour change through the shelf-life of packaged beer. There are several control points in the production of beer where flavour stability may be altered. These include fermentation and the influence of yeast is key. Greater insight into the yeast traits which contribute to flavour stability may help yeast strain selection in the future. Knowledge of the key phenotypes may also lead to improved yeast handing or monitoring practices. In this study, 11 yeast strains, previously characterised according to their sensitivity to oxidative stresses (induced by menadione and hydrogen peroxide) were screened using miniature (100 mL) fermentations and the oxidative stability of the resultant green beer assessed using Electron Paramagnetic Resonance Spectroscopy. The selection of strains with high resistance to multiple oxidative stresses was shown to be a good indicator that yeast would produce a more oxidatively stable beer, although the mechanisms determining this are unknown. The relevance of selecting yeast based on their oxidative sensitivity, their potential to remove metals and sulphur dioxide production are discussed. © 2021 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling

In the past, a variety of herbs were used in brewing, however only hops (Humulus lupulus) are now widely used as they contribute to the bitterness, flavour and microbiological stability of beer. After the abolition of prohibition of the cultivation of the Cannabis sativa L. species (the closest relative of H. lupulus), there are now beers infused with cannabis extracts made from all parts of the plant. The variety ‘hemp’ is used as it contains a minor concentration of the psychoactive Δ⁹-tetrahydrocannabinol compared with marijuana. In this review, H. lupulus and C. sativa are compared and the opportunities and constraints for producing cannabis beers are discussed. © 2021 The Institute of Brewing & Distilling

Saccharomyces cerevisiae var. diastaticus is a feared contaminant in the brewing industry, causing super-attenuation and deterioration in beer quality. The aim of this study was to monitor parameters of bottled lager beer contaminated with Saccharomyces cerevisiae var. diastaticus. Two bottled lagers with original extracts of 10.2 and 11.6% (w/w) were inoculated at 3 ± 1 or 300 ± 50 CFU/mL and stored at 8 or 23°C. Changes in the concentration of real extract, alcohol, turbidity, sugars and increase in 4-vinyl guaiacol were monitored over 14 weeks of storage. The most significant changes were observed in beers stored at 23°C for both concentrations of contaminant. Cold storage at 8°C delayed indicators of spoilage associated with contamination by Saccharomyces cerevisiae var. diastaticus. © 2021 The Institute of Brewing & Distilling

Yeast is central to the brewing process and as such deserves great care and attention to ensure it is fit-for-purpose. It is widely accepted that assessment based on simple viability testing is useful but far too blunt an instrument to give much useful information regarding the physiological state of the live yeast cells within the population. The need to address this issue has spawned a plethora of procedures collectively termed ‘vitality tests’. The concept of yeast vitality is nebulous, and this goes some way to explain why no single test has been universally adopted. There is, however, another major flaw in the underlying assumptions of the majority of vitality tests. This is, most are based on bulk samples which ignore heterogeneities within the population of cells being examined.

The asymmetric mode of proliferation of Saccharomyces yeasts means that mother and daughter cells are always unequal. Individual cells have finite lifespans, old cells die and must be replaced with new fitter progeny. We are fortunate in that budding yeasts are widely used as a model cell for studies into ageing in higher eukaryotes and as a result there is a huge and ever-expanding body of literature devoted to this subject. This has shown that yeast populations comprise several distinct sub-populations which respond differently to external messengers. These messengers may be generated by one sub-set of the population and received and acted upon by another indicating a degree of cooperation designed to ensure survival of the whole. Death of individuals within populations can be as a result of the application of lethal external stresses but more usually is a programmed process in which targeted cells commit suicide in an expression of altruism for the greater good of the whole. On reflection, perhaps this is unexpected but perfectly logical behaviour for single celled organisms to adopt.

Most yeast population studies have been performed using haploid laboratory strains cultivated under relatively defined conditions. The industrial scale model is, of course, far removed from this. Brewing yeast strains are very different, and the complexities of serial fermentations and associated yeast handling processes introduce added layers of complexity. Nevertheless, there is every reason to believe that similar population heterogeneities and cooperative behaviour exist within the context of brewing. The thrust of the arguments presented in this article is that we should embrace this and consider individual cells within yeast populations within a fermenter, for example, as being individual free-living components of a multicellular organism. Further, intercellular cooperation is managed by a network of messenger molecules many of which are likely to trigger the global shifts associated in metabolic activities which accompany the reversible passage from growth to quiescence and which coincidentally are likely to be of importance in beer flavour.

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The Korean traditional rice wine, yakju, has been gaining popularity, especially among young consumers. However, research addressing the consumer acceptance of yakju, based on age, has been limited. This study aimed to identify the drivers of liking and disliking for yakju, across different age groups, by comparing the results of a penalty analysis (PA) based on the check-all-that-apply (CATA) method, with those of the partial least squares (PLS) regression. Overall liking and CATA attributes of 12 commercial yakju samples were assessed by 166 consumers. The liking patterns and drivers of liking, obtained in each age group (20’s and 30-50’s), were similar in some attributes, though not completely identical. Both groups identified sweetness and bitterness as ‘must have’ and ‘must not have’ attributes, respectively. Younger consumers preferred yakju with a green apricot flavour while the 30-50’s age group disliked the flavour of alcohol in it. There was strong agreement between the PLS regression and the CATA-based PA, although the latter was more appropriate at the individual consumer level. It is concluded that the combined use of the two sensory methodologies would be preferable for the analysis of consumer perception, and for the optimisation of yakju manufacturing. © 2021 The Institute of Brewing & Distilling

Despite decades of extensive research, beer flavour instability remains a challenge for both brewing and malting industries. Malt impacts the brewing process as well as the quality of the final beer. It also affects the stability of beer flavour, as it delivers to the brewing process various compounds with the potential to compromise the desired flavour characteristics of beer. These include staling aldehydes and their precursors, such as amino acids, reducing sugars, α-dicarbonyls and bound-state aldehydes. In general, the content of these compounds depends on barley variety and quality, the malting regime and final malt quality. Malt that represents a low potential for beer staling, i.e. that has low values of Kolbach Index, heat load, colour, LOX activity, Strecker aldehydes, transition metal ions and high antioxidative activity, leads to beer with enhanced flavour stability. However, the consistent production of malt with the desired quality remains challenging. Approaches to achieve this include adjustment of steeping and germination conditions, allowing control of grain modification and thus, the reservoir of aldehydes precursors. Also, the application of alternative kilning technologies may reduce the applied heat load, responsible for the formation of staling aldehydes and triggering development of the oxidising free radical species. This review provides an evaluation of current knowledge on the contribution of the malting process and malt quality to the formation of beer staling aldehydes. © 2021 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

Not only variety but also terroir may have a significant impact on the biochemical and brewing characteristics of hops and, consequently, on the resulting beer flavour profile. To date, in contrast to variety-specific effects, comprehensive research data on the impact of terroir on hop brewing characteristics are limited. Therefore, the relevance of hop terroir was further explored with three industrially important hop varieties by examining the consequences of terroir-driven variations in hop characteristics on the sensory attributes and qualities of beer. Eight single-hop beers were produced with T90 hop pellets from distinct cultivation regions worldwide: (i) Amarillo hops grown in Germany, Idaho, or Washington, (ii) Cascade hops grown in Australia, Germany, or Washington, and (iii) Centennial hops grown in Belgium or Washington. Clear biochemical and sensory differences were found between single-hop beers produced with hop pellets of the same variety cultivated in distinct geographical regions. It was confirmed that terroir-related characteristics of hop batches affect the sensory attributes of beer and that the effects are variety dependent. These insights may allow brewers to account for the impact of hop terroir on the consistency and the quality of their beers, while it may open perspectives for subtle diversification in beer flavour profiles. Additional research should further unravel the link between terroir-related hop characteristics and the hoppy aroma and flavour of the resulting beers. © 2021 The Institute of Brewing & Distilling

Beers and other low pH beverages are often stabilised by pasteurisation. There is a lack of guidance as to how many pasteurisation units are required for effective treatment of novel products so as to avoid over-pasteurisation. Yeast are common spoilers of such beverages and some species can produce heat resistant ascospores. As ascospores are more heat tolerant than vegetative cells they are ideal marker organisms for validating the effectiveness of beverage pasteurisation processes. In this study, 63 yeast strains were screened for their ability to produce spores with 30 strains showing different spore configurations. The rate of ascospore development during incubation on sporulation medium was also determined. It was found that the heat resistance of the ascospores of different species/strains varied widely with Saccharomyces species producing some of the most heat tolerant spores. Ascospores of Saccharomyces cerevisiae BRYC 501 were the most heat resistant with significantly more (over 6–16 times) heat resistance than heat tolerant lactic acid bacteria. The D- and z-values of Saccharomyces cerevisiae BRYC 501 ascospores were determined in alcoholic and non-alcoholic versions of two lager beers (American and German). The spores were over 14–18 times more heat tolerant in the non-alcoholic beers and, accordingly, higher PUs need to be applied. Interestingly, at the same/similar alcohol concentration and pH the yeast ascospores were significantly more heat resistant (1.9–2.5 times) in the American than the German beer which may suggest that bitterness contributed to their heat resistance. © 2021 The Institute of Brewing & Distilling

Beer contains the vitamins pyridoxine (B₆) and folates (B₉); their content is variable and depends on several factors. The aim of this study was to investigate the level of these vitamins during large and small scale brewing so as to identify the steps that can influence their levels in the final product. A Golden Ale and Scottish Ale were brewed at sales gravity in a 12 hL plant and a Gold Lager from a bottom fermented high gravity wort at a commercial scale. The levels of pyridoxine at mash-in differed between the brewing processes, due to the different malt used. Pyridoxine levels decreased during mashing while the pyridoxamine concentration remained constant. Although an increase of pyridoxine was observed after the fermentation, its level decreased in the final beers from the large scale process reflecting dilution and pasteurisation. With regard to folates, the levels increased during mashing, decreased after wort boiling and increased during fermentation. This study showed that both pyridoxine and folates were solubilised during the process and remained in the final product. © 2021 The Institute of Brewing & Distilling