Draught beer hygiene: a survey of on‐trade 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. © 2018 The Institute of Brewing & Distilling     

Draught beer hygiene: cleaning of dispense tap nozzles

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 © 2016 The Institute of Brewing & Distilling     

Breeding of lipoxygenase‐1‐less malting barley variety ‘Satuiku 2 go’

The lipoxygenase‐1‐less (LOX‐less) trait has positive effects on beer quality, in particular, improvement of flavour stability related to the reduction of beer‐deteriorating substances such as trans‐2‐nonenal. ‘Ryohfu’ is the only spring‐sown malting barley variety grown in Hokkaido, located in the northern part of Japan, and has been used in the Japanese brewing industry for over 20 years. ‘Satuiku 2 go’ was developed as the first LOX‐less malting barley variety in Japan by successive back‐crossing with molecular marker‐assisted selection to introduce the LOX‐less trait into the recurrent parent ‘Ryohfu’. The agronomic performance and general malt quality of ‘Satuiku 2 go’ were almost equivalent to those of ‘Ryohfu’. Wort and beer analyses at the pilot‐scale brewing trial indicated that the LOX‐less trait had little effect on the general characteristics. In contrast, the beers made from ‘Satuiku 2 go’ malt exhibited reduced levels of trans‐2‐nonenal and trihydroxyoctadecenoic acid. The sensory evaluation demonstrated the superiority of ‘Satuiku 2 go’ beers stored under differing conditions in terms of staleness. It can be concluded that the LOX‐less trait was effective in different genetic backgrounds of the recurrent parents used for the development of LOX‐less malting barley varieties. Copyright © 2018 The Institute of Brewing & Distilling     

AN IMPROVED METHOD FOR MEASURING BEER FOAM COLLAPSE

An automated method for the measurement of beer foam collapse time is described. The method uses a photocell detection unit and a timer which measures the time taken for sufficient light to pass through the collapsing foam. A novel standard dispense method, suitable for beer of greater than 2·0 vols of CO₂ is also described. The method is intended for the rapid asssessment of the foam stability of smallpack beers for routine quality control purposes.     

纯生啤酒的特点和生产管理的重点

主要叙述了纯生啤酒的特点,进一步阐述了纯生啤酒生产过程中如何控制生产工艺、无茵过滤和无菌灌装等重点工序,严格实现无茵化操作,从而实现生产出优质的纯生啤酒.     

无菌瓶装纯生啤酒灌装新工艺

<正> 无菌瓶装纯生啤酒已成为世界啤酒市场的潮流,深受各国消费者的欢迎。由于这种生产工艺还不成熟,目前生产商所要面对的是产品的稳定性和长期存放能力的考验。虽然产品多为使用一次性的玻璃瓶,但也要求灌装线对包装物有较高的杀菌能力和防止二次染菌的功能。为此,市场上便推出了一套崭新的工艺技术,以配合这个潜力巨大的市场发展。     

The sensory evaluation of 2,4,6‐trichloroanisole in wines

This work proposes a sensory method to verify the ‘cork taint’ defect in food and beverages. This off‐flavour has considerable economic impact in wine but occasionally can occur in other food and beverages. In wine, 2,4,6‐trichloroanisole (TCA) is generally considered to be the main compound responsible for this taint. It is an easily recognized compound because of its low sensorial threshold, and it is described as a mouldy and damp cardboard odour. This sensory method, developed in wine, consists of specific panel training to recognize TCA in a series of olfactory tests. The effectiveness of the panel was tested with contaminated wines in which the TCA content had been previously determined by Solid Phase Microextraction‐Gas Chromatography Mass Spectrometry (SPME‐GC/MS) analysis. This sensory method is useful to train a panel able to recognize the ‘cork taint’ defect in different situations (legal appraisals or quality assurance systems). The use of a reliable sensory assay can reduce the number of chemical analyses and the proposed method can be applied to other beverages such as beer. Copyright © 2015 The Institute of Brewing & Distilling     

125th Anniversary Review: Bacteria in brewing: The good,the bad and the ugly

Beer is a beverage that is produced in a multistage process, where some stages of that process are intentionally influenced by microorganisms, while at other stages of the production process microorganisms are actively discouraged. Most of the intentional microbial activity is facilitated by yeast; however bacteria also play an influential role in beer production. This paper will describe the beneficial role of bacteria in the beer production process (the Good), but will also pay due attention to the negative influences bacteria might have on the quality of beer as a commodity (the Bad), and the properties of beer that have given it the status of an inherently safe food for human consumption with regards to disease‐causing bacteria (the Ugly). Copyright © 2013 The Institute of Brewing & Distilling     

The antimicrobial effect of thyme essential oil, nisin and their combination against Escherichia coli O157:H7 in minced beef during refrigerated storage

The antimicrobial effect of thyme essential oil (EO) at supplementation levels of 0.3%, 0.6% or 0.9%, nisin at 500 or 1000 IU/g, and their combination, on Escherichia coli O157:H7 was examined in both tryptic soy broth (TSB) and minced beef meat. EO at 0.3% possessed a weak antibacterial activity against the pathogen in TSB, whereas at 0.9% showed unacceptable organoleptic properties in minced meat. Thus, only the level of 0.6% of EO was further examined against the pathogens in minced meat. Treatment of minced beef meat with EO at 0.6% showed an inhibitory activity against E. coli O157:H7 during storage at 10 °C, but not at 4 °C. Treatment of minced beef meat or TSB with nisin at 500 or 1000 IU/g did not show any antibacterial activity against E. coli O157:H7. The combination of EO at 0.6% and nisin at 500 or 1000 IU/g showed an additive effect against the pathogen, which was higher during storage at 10 °C than at 4 °C.     

Influence of hop harvest date of the ‘Mandarina Bavaria’ hop variety on the sensory evaluation of dry‐hopped top‐fermented beer

To impart a special hop aroma to beer, dry‐hopping is a technique that is becoming more and more popular with commercial breweries. Nevertheless, until now little was known about the factors that influence the reproducibility (and consistent product quality) of dry‐hopping with flavour varieties. One factor that could influence the sensory impressions and aroma profile compositions of dry‐hopped beers is the hop harvest date. Therefore, to determine the effects of different harvest dates of the flavour variety ‘Mandarina Bavaria’ on the aroma of top‐fermented beer, laboratory‐scale dry‐hopping trials were performed. Besides tasting sessions of brewed beers, relative quantities of selected hop‐derived, as well as beer‐originated aroma compounds, were investigated by headspace–solid‐phase microextraction–gas chromatography–mass spectrometry. Duo–trio tests between the beers hopped with pellets of different harvest dates showed no significant differences (α = 0.05) between them. In addition, these beers had similar profiles in a five‐point profile tasting scheme. On the other hand, relative concentrations of some hop‐derived aroma compounds – especially myrcene, which is known to be able to contribute to beer flavour – increased corresponding to a later harvest date, while beer originated volatiles were not different between the beers. Analytical results combined with the results of sensory evaluations led to the conclusion that the harvest date of Mandarina Bavaria was not a dominant factor in the dry‐hopping aroma of top‐fermented beers. High amounts of fermentation by‐products are likely responsible for masking effects resulting in no sensory distinctness between the samples with different hop aroma compound concentrations. Copyright © 2016 The Institute of Brewing & Distilling     

Pilot‐scale brewing using self‐cloning bottom‐fermenting yeast with high SSU1 expression

A pilot‐scale fermentation was performed using SSU1‐overexpressing bottom‐fermenting yeast strains constructed by ‘self‐cloning’. In these strains, the gene SSU1, encoding a plasma membrane protein that excretes sulphite, was highly expressed. The rate of fermentation of the two SSU1‐overexpressing strains tested showed some reduction during the mid‐fermentation phase as compared with the parental strain. These differences, however, did not affect overall fermentation and the final apparent extracts had decreased to a level normally obtained during brewing. The concentration of hydrogen sulphide in the wort remained low during fermentation in the case of the two self‐cloning strains compared with the parent. The concentration of 2‐mercapto‐3‐methyl‐1‐butanol, a sulphur compound that causes an ‘onion‐like’ off‐flavour, was also reduced in the case of the self‐cloning strains, a result confirmed by sensory evaluation of the beer immediately after bottling. Furthermore, with these strains the anti‐oxidation potential of bottled beer, as measured by electron spin resonance, was improved and the concentration of trans‐2‐nonenal in bottled beer after 7 days of accelerated aging at 37°C was decreased. These observations, together with the lower stale flavour score determined by sensory evaluation of bottled beer after a month of aging at 25°C, indicated that the flavour stability of the beer had been successfully improved. Copyright © 2013 The Institute of Brewing & Distilling     

蛋白酶抑制剂对纯生啤酒泡沫稳定性影响

纯生啤酒因未经巴氏灭菌而残留一些酶类,其中具有活性的蛋白酶A及非活性的蛋白酶A前驱物的存在会直接或间接地破坏纯生啤酒的泡沫蛋白,从而使纯生啤酒的泡沫稳定性降低。通常情况下,纯生啤酒中PrA的含量为10^-3TU～10^-5TU。纯生啤酒中蛋白酶A的含量与泡沫稳定性之间有着直接的关系,蛋白酶A及其前驱物的总量决定着降解成品啤酒中泡沫蛋白的综合能力。当蛋白酶A的含量大于10^-4TU时,纯生啤酒的泡沫稳定性就会受到较大的影响。本实验采用热水抽提、乙醇分级沉淀等步骤从灵芝真菌中分离提取一种特异性的蛋白酶抑制剂,用于抑制纯生啤酒中PTA的活性。实验表明,一定条件下,抑制率达75％。在成品纯生啤酒中添加适量的蛋白酶A抑制剂可使纯生啤酒的泡沫稳定性明显提高。     

THE OCCURRENCE OF TWO GEOMETRICAL ISOMERS OF 2,4,5-TRIMETHYL-1,3-DIOXOLANE IN BEER

Two geometrical isomers of 2,4,5-trimethyl-1,3-dioxolane have been detected in a range of commercial and experimental beers at levels up to ca 0.1 ppm. These compounds, plus a number of other dioxolanes, are present in unboiled wort but are lost by evaporation during wort boiling. The trimethyldioxolanes are then reformed during subsequent fermentation. The flavour threshold of a mixture of the two trimethyldioxolanes was found to be ca 0.9 ppm, at which concentration it produced in beer ‘phenolic’ and ‘astringent/drying’ flavour notes. However, these compounds are not present in sufficiently high concentrations to make a significant contribution to the flavour of beer.     

A study on kinetics of beer ageing and development of methods for predicting the time to detection of flavour changes in beer

The kinetics of beer ageing were studied based on the development of beer stale flavour with storage time. Results showed that the beer ageing rates at 50 and 60°C were 30.0 and 56 times as fast as those at room temperature, respectively. Based on these findings, two methods (method A and B) for predicting the ‘time to detection of flavour change’ (TDFC) of beer were developed. TDFC is the beer shelf‐life in terms of flavour stability. In method A, beers were stored in a 50°C water bath and the intensity of beer ageing was scored daily. Thus, the range of TDFC of the beer was acquired according to the maximum number of days within which the intensity of beer ageing was ≤2 and the minimum number of days within which the intensity of beer ageing was >2. In method B, the 2‐thiobarbituric acid (TBA) values of a beer were determined before and after 1 day of storage in a 50°C water bath, and the TDFC of the beer was calculated using the equation: where ΔTBA is the increment of TBA value during 1 day of storage at 50°C. Both methods were simple, rapid and accurate. Copyright © 2015 The Institute of Brewing & Distilling     

The multisensory perception of hop essential oil: a review

Hops are a key ingredient to add bitterness, aroma and flavour to beer, one of the most consumed beverages worldwide. Essential oils from different hop varieties are characterised by similar classes of chemical compounds and complexity, but their contribution to sensory characteristics in beer differs considerably. Volatiles in hop oil are categorised into several chemical classes. These induce diverse aroma and flavour sensations in beer being described as ‘floral’, ‘fruity’ (e.g. contributed by alcohols, esters, sulphur-containing compounds), ‘spicy’, ‘woody’, ‘herbal’ (sesquiterpenes, oxygenated sesquiterpenoids), and ‘green’ (aldehydes). The perception of hop volatiles depends on their concentrations and combinations, but also on threshold levels in different beer matrices or model systems. Several studies attributed modified taste and mouthfeel sensations to the presence of hop volatiles contributing to a multisensory perception of hop flavour. Linalool is frequently observed to show additive and synergistic-type behaviour and to affect aroma perception if combined with geraniol. Linalool has also been found to be involved in aroma-taste interactions, modifying the perception of bitterness qualities in beer. Particularly oxygenated sesquiterpenoids are suggested to be responsible for an irritating, tingling sensation indicating the activation of trigeminal receptors. The majority of these sensory interactions have been discovered almost by accident and a systematic research approach is required to gain a broad understanding of these complex phenomena. This review provides an overview of factors affecting the perception of hop derived volatiles involved in different sensory characteristics of beer, while illustrating the latest advances and highlighting research gaps from a sensory science perspective. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling     

Differences in protein content and foaming properties of cloudy beers based on wheat malt content

To investigate differences in protein content, all barley malt beer, wheat/barley malt beer and all wheat malt beer were brewed, and the protein during mashing, wort, fermentation and beer determined. It was shown that protein was mainly extracted during mashing and the protein rest phase, decreased in the early stages of fermentation and remained almost steady during wort boiling and cooling, in the middle and late stages of fermentation. By separating beer foam from beer, similar protein bands of 51.7, 40.0, 27.3, 14.8, 6.5 and < 6.5 kDa appeared in the three beers, defoamed beers and beer foams using the sodium dodecyl sulphate polyacrylamide gel electrophoresis. Quantitatively, protein bands of 6.5–14.8 and <6.5 kDa had the highest contents in the three beers. Unique bands at 34, 29.2, 23.0, 19.7 and 17.7 kDa were found in beer, defoamed beer and beer foam from wheat beer and all‐wheat malt beer, respectively. Wheat beer foam showed the best foam stability and the protein in all barley malt beer showed the best migration to the foam. The beer foam properties were influenced by not only protein content but also protein characteristics and/or origin. It is suggested that the barley malt contributed the beer foam ‘skeleton protein’ while protein components from wheat malt kept the foam stable. © 2018 The Institute of Brewing & Distilling     

Comparative analysis of the fermentation performance of high‐quality milk beer strains (Kluyveromyces marxianus) and optimisation of medium formula for high‐density fermentation

Milk beer is a new type of dairy beverage in China and increasingly popular with consumers. The strain FXJ1 isolated in our laboratory was an excellent strain for the production of milk beer with alcohol content of 0.48%. Our research verified that the strain FXJ1 was superior to the commercial strain MJ for milk beer production and got the optimal medium formula (67.37 g/L sucrose, 29.7 g/L yeast extract, 15.61 g/L corn steep liquor, 4.13 g/L KH₂PO₄ and 0.3 g/L MgSO₄) which allowed the biomass production of strain FXJ1 to achieve 8.88 ± 0.08 g/L and increase 2.94‐fold as compared with yeast extract peptone dextrose base medium.     

A SIMPLE METHOD FOR TESTING BEER FILTERABILITY

Based on a filtration manifold from ‘Millipore’ a method was developed which permits the simultaneous investigation of the filterability of up to ten beer samples. Characteristics of the simple apparatus are the use of sheet filters, a vacuum filtration at room temperature and very small sample volumes. An excellent correlation to the differential pressure at the industrial filter was found, demonstrating the reliability of the test for routine applications. The usefulness of the method for research applications was demonstrated in experiments with enzymes improving beer filtration.     

Enhanced Quantitative Extraction and HPLC Determination of Hop and Beer Bitter Acids

A pleasant and consistent bitterness is an essential flavour attribute of beer. Hop‐derived iso‐α‐acids are largely responsible for beer bitterness and accurate determination of these primary flavour compounds is very important in relation to quality control. The most widely used way to determine beer bitterness is based on spectrophotometry, measuring the absorbance of an iso‐octane extract of acidified beer. However, this approach is far from specific as it measures all of the extracted compounds, including non‐bittering principles. For that particular reason, High Performance Liquid Chromatography (HPLC) is increasingly applied for the quantitative determination of hop‐derived iso‐α‐acids and, if present, reduced iso‐α‐acids. However, to obtain accurate data on beer bitterness profiles, both quantitative sample preparation and state‐of‐the‐art HPLC are essential. In this paper, several extraction procedures based on solid phase extraction (SPE) and liquid‐liquid extraction (LLE), respectively, were evaluated and an optimised extraction methodology using H₃PO₄ for sample acidification prior to extraction is presented. The proposed extraction/HPLC methodology allows for the quantitative recovery and analysis of hop‐derived beer bitterness.     

微膜过滤法无菌鲜啤酒生产工艺设计研究

采用膜错流过滤和新型的无菌灌装系统的消毒灭菌方法对无菌生啤酒的生产工艺进行设计 ,使整个生产工艺系统高效、优化运行 ,同时加强生产操作及卫生的管理 ,生产出色泽、品质优良、保质期长的无菌鲜啤酒