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     

Chilling injury development of ‘Tahitian’ lime, ‘Emperor’ mandarin, ‘Marsh’ grapefruit and ‘Valencia’ orange

The effect of varying levels of ethylene on the chilling injury (CI) development and the changes in the levels of putrescine, squalene and α-farnesene of ‘Tahitian’ lime (Citrus latifolia Tanaka), ‘Emperor’ mandarin (Citrus reticulata Blanco), ‘Marsh’ grapefruit (Citrus paradisi Macf) and ‘Valencia’ orange (Citrus sinensis L Osbeck) stored at 0°C was investigated. It was found that different citrus fruits stored at 0°C had varying sensitivity to CI, and that low levels of exogenous ethyiene induced earlier and more severe CI in all citrus fiuits. The levels of endogenous putrescine, squalene and α-farnesene varied between fruit, and was affected by the time of exposure at 0°C and the presence of ethylene. The patterns of change indicate that loss of squalene coupled with loss of α-farnesene could be involved in induction of CI.     

啤酒稳定性的研究进展

本文总结了目前国内啤酒风味稳定性、非生物稳定性、生物稳定性方面的研究成果，对最终攻克这个顽症有一定的参考价值。     

Effects of wax coatings and postharvest storage on sensory quality and aroma volatile composition of ‘Mor’ mandarins

BACKGROUND: Mandarins suffer from accumulation of off‐flavours after harvest. In this study the sensory quality and aroma profile composition of homogenised segments of untreated (control) and wax‐coated ‘Mor’ mandarins after 7 days at 20 °C or 3 or 6 weeks of cold storage at 5 °C were examined. RESULTS: Fruit taste score decreased during storage and following wax coating, and this was attributed to decreases in sourness and mandarin flavour and accumulation of off‐flavours. Aroma profiling identified 31 volatiles that decreased by at least 50% during storage and after waxing and thus may be involved in the observed flavour loss. In contrast, 13 volatiles, mostly belonging to ethanol fermentation and fatty acid and amino acid catabolism pathways, significantly increased at least twofold and probably contributed to off‐flavour enhancement. CONCLUSION: The results showed that after harvest there was a progressive decrease in sensory quality of ‘Mor’ mandarins. It is proposed that observed decreases in contents of sesqui‐ and monoterpenes and short‐chain oxygenated fatty acids may contribute to the decrease in mandarin flavour, whereas increases in the contents of ethanol fermentation metabolites and derivates of fatty acid and amino acid catabolism are most likely involved in causing the enhanced sensation of off‐flavours. Copyright © 2010 Society of Chemical Industry     

Preliminary characterization of an Italian craft durum wheat beer

In recent years, there has been increasing interest in the production of beers brewed using raw materials of local origin. Many micro‐breweries have been established in Italy, particularly in Sardinia, where some have started to use Sardinian wheat to produce a beer that has a regional connection. The most widespread wheat cultivar used in Italy has been Senatore Cappelli, which is still grown in Sardinia and in some other regions. Bread produced with this type of wheat is characterized by a high protein content and good sensory properties. Owing to its origin, this cultivar is being considered for use in beer production. In this work, a Sardinian durum wheat beer was compared with two other wheat beers brewed in Europe (Germany and the Czech Republic). Standard beer chemical analyses, along with volatile and sensorial profiles, were used to characterize the Sardinian craft durum wheat beer. Copyright © 2014 The Institute of Brewing & Distilling     

The Contribution of 4‐Hydroxyfuranone Derivatives to the Aroma of Commercial Beers and Malts

Analysis of hot water extracts from a range of commercial malts showed that 2,5‐dimethyl‐4‐hydroxy‐3(2H)furanone (DMHF) varied from undetectable (lager malt) to 4.2 mg/litre (crystal malt), a concentration twenty‐six times the flavour threshold in water. 5‐Methyl‐4‐hydroxy‐3 (2H)furanone (MHF) was detected in all samples except one but was always well under its flavour threshold value. 2(or 5)‐Ethyl‐5(or 2)‐methyl‐4‐hydroxy‐3(2H)furanone (EMHF) was not detected in any of the samples. Fermentation of lager, ale and crystal malt extracts with an ale strain of yeast led to the appearance of EMHF in all cases as well as additional DMHF. The greatest increases in both compounds was with the ale malt. Both increases and decreases occurred in MHF concentration as a result of fermentation but final levels were always well below the flavour threshold value. Analysis of ten commercial beers found DMHF in all the samples and in five cases levels exceeded twice the flavour threshold value in beer with flavour units from 2.4 to 9.1. A flavour panel noted that in four of these cases the beer had a distinctly sweet/caramel aroma which is typical of DMHF. EMHF was undetectable in six samples, detectable, but unquantifiable, in three cases but at about 80% of the flavour threshold value in the remaining sample. MHF was found in all samples but at insignificant levels. The results show that DMHF is an important flavour compound in British ales and EMHF may make a contribution in a limited number of situations. The contribution of malt type, brewery processing and yeast strain in determining the concentration of the two 4‐hydroxyfuranones in beer remains uncertain.     

The relationship between flavour instability,preference and drinkability of fresh and aged beer

The preference and drinkability of fresh beer compared with aged beer was tested using a ‘paired comparison test’. After a duo test with small samples, respondents could freely consume the beer of their choice. The results show that the initial preference for fresh beer was significantly higher than the preference for aged beer, with 65% of respondents taking fresh beer first after the duo test. The drinkability of fresh beer also scored significantly higher, with 35% more fresh beer consumed. However, since multiple respondents consecutively consumed multiple aged beers, it cannot be concluded that aged beer results in a lower consumption volume (per capita) when compared with fresh beer. Additionally, Belgians older than 24 years particularly favoured and consumed the fresh beer in the experiment. This was attributed to the influencing and mimicking behaviour of the other respondent groups, since the table setting and table sizes were also found to be important parameters. In this paper, we show the continuing importance of research into beer flavour stability. © 2019 The Institute of Brewing & Distilling     

Identification of aroma‐active compounds in fresh and stored ‘Mor’ mandarins

In this study, gas chromatography–olfactometry (GC‐O) (sniffing) combined with gas chromatography–mass spectrometry (GC‐MS) analysis was applied to identify volatile aroma‐active compounds in homogenised segments of fresh and stored ‘Mor’ mandarins. The GC‐O nasal impact frequency method was used to identify Twenty‐three aroma‐active compounds, of which seventeen odorants were identified by GC‐MS. The aroma of fresh ‘Mor’ mandarins derived from a mixture of eleven odorants that contribute ‘green’ [(E)‐3‐hexenol and hexanal], ‘fresh’ [(E)‐carveol], ‘fruity’ (ethyl 2‐methylbutanoate), ‘citrus’ (limonene), ‘floral’ (linalool), ‘musty’ (β‐myrecene and γ‐terpinene), ‘potato’ (α‐terpinene), ‘mushroom’ (unknown 2) and ‘cabbage’ (α‐cubebene) odours. During postharvest, storage losses were observed in ‘green’ [(E)‐3‐hexenol] and ‘fresh’ [(E)‐carveol] odours, accompanied by increases in ‘fruity’ (ethyl propanoate) and several unpleasant aromas, such as ‘alcohol’ (ethanol), ‘musty’ [α‐pinene, (E)‐2‐nonenal and 1‐terpinen‐4‐ol] and ‘fatty’ (octyl acetate and δ‐cadinene) odours, all of which possibly account for the observed decrease in sensory acceptability after harvest.     

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     

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     

高效液相色谱分析啤酒中的肌苷、肌苷酸

采用Nova-pak C18色谱柱(150×3.9mm id,4μm),水(含0.5%H3PO4)、甲醇为流动相,梯度洗脱,流速0.60mL/min,柱温30℃,测定波长(λ)248nm,直接进样同时分离了肌苷和肌苷酸。结果显示,在肌苷、肌苷酸含量分别为0.5mg/L～10mg/L时,呈线性关系,加样平均回收率为91.6%、96.8%,相对标准偏差为0.8%～2.6%。     

Occurrence of sotolon,abhexon and theaspirane‐derived molecules in Gueuze beers. Chemical similarities with ‘yellow wines’

The typical Belgian Gueuze beers are produced with aged hop from a grist of malt and wheat, according to a very long oxidation process (extended boiling, cooling overnight in an open‐air container, oak‐barrel ageing). Two theaspirane‐oxidation‐derived products, dihydrodehydro‐β‐ionone and 4‐hydroxy‐7,8‐dihydro‐β‐ionone, are evidenced here for the first time in Gueuze beers. Both compounds have been recently identified in oxidative wines such as Jura Flor‐Sherry and Sauternes wines. Another analogy with Jura Flor‐Sherry wines was the presence of the nutty/curry odorants sotolon and abhexon, although at lower concentrations. Copyright © 2012 The Institute of Brewing & Distilling     

Toxicity profile of commercially produced indigenous banana beer

Mycotoxins, together with endotoxins, represent important classes of naturally occurring contaminants in food products, posing significant health risks to consumers. The aim of this study is to investigate the occurrence of both Fusarium mycotoxins and endotoxins in commercially produced traditional banana beer. Two brands of commercially produced traditional banana beer were collected from a local retail market in Kigali, Rwanda. Beer samples were analysed for the presence of deoxynivalenol (DON), fumonisin B₁ and zearalenone (ZEA), using an enzyme-linked immuno-sorbent assay (ELISA) method. The quantification of bacterial endotoxin using Limulus amoeboecyte lysate (LAL) assay was also conducted. The contamination levels were 20 and 6.7?µg?kg^?1 for DON; 34 and 31.3?µg?kg^?1 for FB₁; 0.66 and 2.2?µg?kg^?1 for ZEA in brands A and B of the beers, respectively. Results indicate that the levels of Fusarium toxins and bacterial endotoxin reported in this study did not pose adverse human health effects as a result of drinking/consuming banana beer. However, exposure to low/sub-threshold doses or non-toxic levels of endotoxins magnifies the toxic effect of xenobiotic agents (e.g. fungal toxins) on liver and other target organs. Considering Fusarium toxins and/or endotoxin contamination levels in other agricultural commodities intended for human consumption, health risks might be high and the condition is aggravated when beer is contaminated by mixtures of the mycotoxins, as indicated in this study.     

Fate of 2‐sulphanylethyl acetate and 3‐sulphanylpropyl acetate through beer aging

Sulphanylalkyl alcohols and their corresponding acetates were investigated in 14 commercial Belgian beers. Although it was the major peak at the pulsed‐flame photometric detector, the empyreumatic 2‐sulphanylethyl acetate was found at concentrations below its individual odour threshold, estimated at 40 µg/L (0–4 µg/L in most fresh beers, 5–12 µg/L in three fresh high‐bitter beers). Both the Ehrlich pathway and hop constituents contribute to this content. In 11 of the investigated samples, synthesis of 2SE‐A and 3‐sulphanylpropyl acetate (roasted, burned) continued during the first three months of storage. Although below their individual thresholds, these compounds might interact by synergy with other aged flavours. As yeast was absent from most of the investigated bottles, chemical degradation of precursors is suspected. Copyright © 2012 The Institute of Brewing & Distilling     

Analytical‐Sensory Determination of Potential Flavour Deficiencies of Light Beers

Although currently light beers have a high market share in the US, this beer style is still not accepted on the European continent because light beers are considered watery, mainly on account of lack of mouthfeel. In this paper, the flavour quality, including flavour stability, of five commercial light beers was evaluated in comparison with their corresponding pilsner beers derived from the same breweries. Through detailed physico‐chemical and sensory evaluation, followed by multivariate data analysis, the fresh beers could be differentiated according to their origin (US or European) and beer style (light or pilsner). Potential flavour deficiencies of fresh light beers were determined as too much sweetness, lack of bitterness, and especially reduced fullness. As a result, the fresh light beers were less preferred than their corresponding pilsner. Upon ageing, the light beers were generally less flavour stable than their pilsner counterparts. This is mainly ascribed to increased sensory perception of cardboard and ribes staling flavours in most aged light beers. Nevertheless, based on detailed analytical/sensory investigation, it was clearly demonstrated that one of the light beers involved in this study showed enhanced flavour stability with respect to all other beers, including the pilsner beers.     

仙人掌啤酒的研制

经过研制在啤酒生产中按3％～4％的比例加入处理后的仙人掌汁，制成仙人掌保健啤酒。这种保健啤酒具有独特的抗癌、降脂、降糖、降压及减肥功效，深受消费者喜爱。     

Relationship of iso‐α‐acid content and endogenous antioxidative potential during storage of lager beer

One of the critical issues regarding the quality of beer is the change in its chemical composition that occurs during storage. Decomposition of iso‐α‐acids results in an undesirable decrease in bitterness as well as a deterioration in the sensory profile of the beer. These changes are caused by the susceptibility of iso‐α‐acids to degradation owing to the influence of reactive oxygen species and light. The aim of this study was to investigate the influence of storage conditions (temperature, light) on the degradation of iso‐α‐acids during aging, with the main focus on monitoring the relationship between the turnover of iso‐α‐acids, the sulphur dioxide content and the antioxidative potential of stored beer as measured by electron spin resonance spectroscopy. In agreement with previous investigations, a significant decrease in the content of bitter compounds (up to 18 % relative to the original level, depending on storage conditions) was observed. A significant decrease in the antioxidant potential of beer was recorded simultaneously and the data confirmed a strong correlation between these parameters. The decline in beer bitterness could become a marker for estimating oxidative damage during storage. Copyright © 2014 The Institute of Brewing & Distilling     

Formation of 4‐Hydroxyfuranones and their Precursors during Production of Worts and Beers

Laboratory beers and samples taken at each stage of production, were analysed for the flavour active 4‐hydroxyfuranones; 5‐methyl‐4‐hydroxy‐3(2H)‐furanone (MHF), 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone (DMHF) and 5‐(or 2)‐ethyl‐2(or 5)‐methyl‐4‐hydroxy‐3(2H)‐furanone (EMHF). The length and temperature of mashing, the length of boiling, the rate of cooling the worts and the effects of grist composition were investigated to identify the 4‐hydroxyfuranone content of worts and subsequent beers. Fermentation temperature and the use of the stabilising agents, PVPP and Lucilite PC5, on the 4‐hydroxyfuranone content of the beer was also investigated. The results demonstrated that several aspects of beer production procedures affect the furanone content of the beer, but in practice the important factors are grist composition, the rate at which the boiled wort is cooled and fermentation temperature. Fermentation has a major effect on final furanone content as yeast produces both DMHF and EMHF. The results suggest that malt levels of precursor compounds, which can be converted to 4‐hydroxyfuranones by the Maillard reaction or by yeast, may prove to be more important than the quantities of the furanones found in malt in determining the final furanone content of beer. A clearer understanding of the nature of the precursors should allow manipulation of their production and beer furanone content.