Role of Strecker aldehydes on beer flavour stability

In this work, attempts were made in order to measure the importance of “Strecker aldehydes” on flavour stability of beer correlating chemical and sensory data. It has been observed that methional and phenylacetaldehyde accumulates during storage and that these molecules were well correlated with “Aroma Quality”. A “fresh beer” was spiked with methional, phenylacetaldehyde and also with trans-2-nonenal, singly and in combination, the “Similarity Value” was then determined, between samples and an “aged beer”. The highest value was 72 % when the three compounds were added simultaneously and the combination of the two Strecker aldehydes increases by 54 % the degree of similarity

Characterization of craft beer through flavour component analysis by GC-MS and multivariate statistical tools

Beer is a rather popular drink and represents the most widely consumed alcoholic beverage in the world.The present research aims at characterizing the flavour profile of lager pilsner, the category of low fermentation beers most common in Europe. The largest portion of the global market is dominated by a few multinational companies, but in the last years the number of independent craft breweries has increased very rapidly also in countries where there weren’t an established craft brewing tradition. According to the Italian Brewers Association, in Italy there are eight brewing companies which operate 14 industrial breweries, which in the years have standardized the product to increase their slice of market. The craft-beer sector represents a niche market, about 3% of total production (1% in 2011) [EU Report, 2016]. Italy has a relatively young craft brewing tradition, but the data together with the new ways of consumption, can be considered promising for the sector development. In 2016, the “craft beer” has been defined for the first time in Italy with DDL 1328-B (art.35). Legislation does not consider the quality of the raw materials, but only the manufacturing processes: the artisanal beer-making is a beer obtained without microfiltration and pasteurization steps, unlike industrial products. In this contest, the aim of the study was to characterize the beers (all lager style) purchased on the market through the analysis of the aromatic profile of samples produced under different processes (craft methods or industrial processes). In fact, in addition to smaller production scale and independent, the main characteristic of craft beer is to put the emphasis on flavour and brewing techniques. Flavour, consisting of a large number of volatile compounds, has a great influence on consumer acceptability and, when safety and nutritional value are guaranteed, sensory parameters become the discriminating factor in the product quality assessment which determines the differentiation on the market. The identification of specific compounds, which confer a particular aroma, suitable to be used as potential quality/process markers in order to discriminate beer samples according to their production method. A headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) was performed to evaluate the beer samples fingerprint. Multivariate statistical methods were then applied to the collected profiles to built model which could allow differentiating craft beers from all the others. Hence, the proposed method may represent an interesting tool to authenticate craft beer by verification of the compliance with their label description which, at the same time, can entail brand protection

The science of the tropical cereals sorghum, maize and rice in relation to lager beer brewing

Mainstream lager beer brewing using the tropical cereals sorghum, maize and rice, either as malt or as raw grain plus commercial enzymes, is becoming widespread. This review examines the differences in composition between these tropical cereals and barley and their impact on brewing processes and beer quality. All of these cereals have a starch gelatinization temperature some 10 °C higher than barley. The sorghum prolamin proteins are particularly resistant to proteolysis owing to disulphide cross-linking involving γ-kafirin. Unlike barley, the major endosperm cell wall components in sorghum and maize are arabinoxylans, which persist during malting. The rice cell walls also seem to contain pectic substances. Notably, certain sorghum varieties, the tannin-type sorghums, contain considerable levels of condensed tannins (proanthocyanidins), which can substantially inhibit amylases, and probably also other brewing enzymes. Tropical cereal malts exhibit a similar complement of enzymic activities to barley malt, with the notable exception of β-amylase, which is much lower and essentially is absent in their raw grain. Concerning beer flavour, it is probable that condensed tannins, where present in sorghum, could contribute to bitterness and astringency. The compound 2-acetyl-1-pyrroline, responsible for the popcorn aroma of maize and also the major aroma compound in rice, presumably affects beer flavour. However, much more research is needed into tropical cereals and beer flavour. Other future directions should include improving hydrolysis of prolamins into free amino nitrogen, possibly using prolyl carboxypeptidases and investigating tropical cereal lines with useful novel traits such as high amylopectin, high protein digestibility and low phytatehttp://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2050-0416hb201

Flavour formation in continuous fermentations

Fundação para a Ciência e a Tecnologia (FCT

Identification of a Protein with Antioxidant Activity that is Important for the Protection against Beer Ageing

This study was carried out with fresh Australian lager beer which was sampled directly off the production line, the same samples aged for 12 weeks at 30 °C, and the vintage beer which was kept at 20 °C for 5 years. Characteristic Australian lager flavour was maintained in the fresh and vintage beers but was lost in the aged beer. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and free thiol group labelling analyses of beer proteins found that this flavour stability correlated with the presence of an unknown 10 kilodaltons (kDa) protein with a higher level of free thiols. The protein was purified by size-exclusion chromatography, then peptide sequencing and database matching identified it as the barley lipid transfer protein (LTP1). Further characterisation using diphenylpicrylhydrazyl (DPPH) free radical scavenging and a Saccharomyces cerevisiae-based antioxidant screening assay demonstrated that the LTP1 protein was active in DPPH reduction and antioxidant activity. The absence of free thiol in the aged beer indicates that the thiol functional groups within the LTP1 protein were saturated and suggests that it is important in the flavour stability of beer by maintaining reduction capacity during the ageing process

Evolution of staling aldehydes on lager beer stability: impact of maritime transport and storage condidtions

A estabilidade organolética da cerveja engarrafada é atualmente um dos principais desafios da indústria cervejeira. Não obstante à contribuição de inúmeras substâncias, os compostos carbonilos, em particular os aldeídos, são responsáveis por muitas das mudanças desfavoráveis e percetíveis ao consumidor. Estas modificações são favorecidas por temperaturas não refrigeradas, armazenamento durante períodos longos, vibrações induzidas pelo transporte, entre outros fatores. Atualmente, existem ainda poucos dados na literatura científica sobre o impacto das condições reais de transporte, nomeadamente impacto das vibrações e temperaturas não refrigeradas, na estabilidade organolética da cerveja. O presente trabalho teve como objetivo avaliar a evolução de 10 aldeídos em cerveja Lager engarrafada durante exportação por via marítima e armazenamento no destino. Para tal, simulou-se as condições reais que a cerveja produzida localmente é submetida, nomeadamente temperatura (19-30ºC), vibração (1.7 Hz) e tempo (até 120 dias). A análise dos compostos em estudo foi realizada por micro-extração em fase sólida seguida por cromatografia gasosa acoplada a espetrometria de massa. Os resultados obtidos revelaram que as condições de transporte (influência de tempo, temperatura e vibração) e armazenamento (tempo, temperatura) simuladas i) promoveram o aumento médio na concentração dos aldeídos de Strecker, de 65%, ii) enquanto os aldeídos formados a partir oxidação lipídica bem como o acetaldeído, regra geral, não apresentam variações significativas neste período. O aumento descrito em i) apresentou dois padrões: garrafas com abertura tradicional (carica) apresentavam valores médios de 131.6±9.9 e 190.3±9.4 µg/L enquanto garrafas com um sistema de abertura fácil 190.5±10.0 e 180.3±9.5 µg/L, após transporte e armazenamento respetivamente. O fenilacetaldeído foi o composto com maior variação nas condições estudadas, aumentando de 94.7±7.3 (cerveja fresca) para 143.6±8.0 e 168.9±8.9 µg/L, após transporte e considerando um período adicional de armazenamento, respetivamente. Adicionalmente, verificou-se que o procedimento de envelhecimento forçado tipicamente adotado, pode apresentar limitações a reproduzir as condições reais em alguns compostos. Em particular, destaca-se o benzaldeído, que em qualquer período de envelhecimento forçado, 7, 14 e 28 dias, apresentou concentrações, em média, inferiores, de 5.3±0.3 µg/L, 5.4±0.3 µg/L e 5.4±0.3 µg/L, respetivamente, em comparação com o teor real ao fim de 120 dias, de 6.4±0.4 µg/L.The flavour stability of bottled beer is the main challenge of the brewing industry. Carbonyl compounds, in particular aldehydes, are responsible for the unfavourable and perceptible changes detected by consumers. Those modifications are favoured by unrefrigerated temperatures, prolonged storage, transport-induced vibrations, among other factors. Currently, there are few data in the scientific literature on the impact of real transport conditions, namely vibrations and unrefrigerated temperatures, on beer stability. The aim of this study was to evaluate the evolution of 10 aldehydes in bottled Lager beer during maritime exportation and storage at the destination. To this end, the real conditions that the locally produced beer is subjected to, namely temperature (19-30ºC), vibration (1.7 Hz) and time (up to 120 days) were simulated. The analysis of the compounds under study was performed by solid-phase microextraction followed by gas chromatography coupled with mass spectrometry. The results revealed that the conditions of transport and storage simulated i) promoted an average increase in the concentration of Strecker aldehydes of 65%, ii) while the aldehydes formed from lipid oxidation as well as acetaldehyde, in general, do not present significant variations. The increase described in i) presented two patterns: bottles with traditional cap had mean values of 131.6±9.9 and 190.3±9.4 µg/L while bottles with a ring pull cap had 190.5±10.0 and 180.3±9.5 µg/L, after transport and storage respectively. Phenylacetaldehyde was the compound with the greatest variation, increasing from 94.7±7.3 (fresh beer) to 143.6±8.0 and 168.9±8.9 µg/L, after transport and considering an additional storage period, respectively. Additionally, it was found that the forced ageing procedure typically adopted may have limitations in reproducing the real conditions. Benzaldehyde stands out, which in any period of forced ageing, 7, 14 and 28 days, presented concentrations, on average, lower, of 5.3±0.3 µg/L, 5.4±0.3 µg/L and 5.4±0.3 µg/L, respectively, compared to the actual content after 120 days, of 6.4±0.4 µg/L

A review of flavour formation in continuous beer fermentations

The attractive prospect of a continuous beer fermentation system consists mostly of the accelerated transformation of wort into beer. Although continuous beer fermentation has been studied as a promising technology for several decades, the number of industrial applications is still limited. The major obstacle hindering the extensive industrial exploitation of this technology is the difficulty in achieving the correct balance of sensory compounds in the short time typical for continuous systems. This paper offers an integral view on the particularities of continuous systems, which may impart beer a sensorial character distinct from conventionally fermented counterparts. The main groups of flavour active compounds are discussed from the perspective of possible control strategies by means of process parameters and strain selection.Czech Grant Agency; MŠM

Influence of the hopping technology on the storage-induced appearance of staling aldehydes in beer

J. Inst. Brew. 116(4), 381-398, 2010 In this paper, the involvement of iso-alpha-acids in the appearance of stale flavour in beer during storage was examined. Flavour instability upon storage, by far the most important quality problem of beer, may be caused by a multitude of reactions, in particular, the degradation of trans-iso-alpha-acids is pivotal. In order to gain improved understanding of the beer ageing process, the behaviour of the stereoisomers of the bitter acids was studied for the first time in pilot beers at particularly high and low proportions of the trans-iso-alpha-acids concentration relative to the cis-iso-alpha-acids concentration. Therefore, pure trans- respectively cis-isomers were required and obtained on a pilot scale by the separation of trans-iso-alpha-acids as beta-cyclodextrin inclusion complexes from a commercial isomerised hop extract, permitting the quantitative dosage to beer in mg/L amounts. The relationship between the storage-induced degradation of these iso-alpha-acids in authentic beer samples and the increase in staling aldehydes, especially 2-methylpropanal, 2-methylbutanal and 3-methylbutanal, is the subject of further investigations. A remarkable increase in the relative concentration of cis-iso-alpha-acids was observed in the beers bittered with purified trans-iso-alpha-acids, which may be ascribed to partial conversion, i.e., reverse isomerisation, of trans-iso-alpha-acids via alpha-acids into cis-iso-alpha-acids. In spite of the trans-specific degradation observed during ageing, the decomposition of these bitter acids leading to volatile carbonyl compounds is of minor importance. Aldehyde formation as a function of forced ageing was irrespective of the mode of bittering, emphasising that malt quality and the brewing process itself are probably the most important factors regarding the flavour instability of beer

Analytical and sensory assessment of hoppy aroma and bitterness of conventionally hopped and advanced hopped pilsner beers

J. Inst. Brew. 116(4), 445-458, 2010 Analytical and sensory aspects of hoppy aroma of conventionally hopped and advanced hopped pilot Pilsner beers were investigated. Linalool and several sesquiterpenoids were used as analytical markers for the hoppy aroma of the beers. Levels of linalool and sesquiterpenoids in the fresh beers, as well as sensory characteristics of hoppy aroma (intensity and attributed aroma descriptor(s)) clearly depended on the applied hop aromatisation technology and on the type of hop oil fraction used in advanced hopping. The most pronounced hoppy aroma was observed for the advanced bittered beers, either aromatised post-fermentation using a polar hop essence or at the end of wort boiling using pellets (late-hopping). However, all refined hop oil fractions used in this study for advanced aromatisation clearly affected the hoppy aroma impression. Analytical data on staling indicators, combined with sensory evaluations, further suggest that hop oil preparations may also affect flavour stability of the resulting beers in a positive way. In general, it can be concluded that hop aromatisation, whether performed in the advanced or conventional way, appears to mask beer staling, as demonstrated by lower overall sensory ageing scores

Ultra DNA Barcoding for Identification of Hop Varieties

Hops (Humulus lupulus) are increasingly becoming an important cash crop in BC primarily used to give beer a characteristic aroma and bitterness. There are over 100 different varieties of hops, and each can impart a different beer flavour profile. In recent years, beers with unique combinations of hop varieties, mainly India pale ales or IPAs, have markedly increased in popularity and have been a cornerstone of BC’s burgeoning craft brewing industry. However, distinguishing them based on morphological characters alone can be difficult. An efficient and reliable DNA marker-based genotyping method is needed. Chloroplast DNA is ideal for identifying hop varieties because it is maternally inherited, and the hops are the female flowers of the hop plant. Our goal is to develop a DNA barcoding system using whole chloroplast genomes (i.e. ultra-barcoding) for identification of hop varieties