Alcohol-free and low-alcohol beers: aroma chemistry and sensory characteristics

Alcohol-free beers have gained popularity in the last few decades because they provide a healthier alternative to alcoholic beers and can be more widely consumed. Consumers are becoming more aware of the benefits of reducing their alcohol consumption, and this has increased the sales of non-alcoholic alternatives. However, there are still many challenges for the brewing industry to produce an alcohol-free beer that resembles the pleasant fruity flavor and overall sensory experience of regular beers. The aim of this review is to give a comprehensive overview of alcohol-free beer focusing on aroma chemistry. The formation of the most important aroma compounds, such as Strecker aldehydes, higher alcohols and esters, is reviewed, aiming to outline the gaps in current knowledge. The role of ethanol as a direct and indirect flavor-active compound is examined separately. In parallel, the influence of the most common methods to reduce alcohol content, such as physical (dealcoholization) or biological, on the organoleptic characteristics and consumer perception of the final product, is discussed

Elucidating the odor-active aroma compounds in alcohol-free beer and their contribution to the worty flavor

Alcohol-free beers (AFB) brewed by cold-contact fermentation exhibit a flavor reminiscent of wort which affects consumer acceptability. The aims of this study were to identify the odor-active compounds in AFB and elucidate the contribution of these to the overall aroma and worty character of the beer. Using a sensomics approach, 27 odor-active aroma compounds were identified and quantitated using GC-MS. The most odor-active compound was methional (boiled potato-like aroma), followed by 3-methylbutanal (cocoa-like), (E)-β-damascenone (apple, jam-like), 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone (curry, spicy-like), and phenylacetaldehyde (floral, honey-like). The important contribution of these flavor compounds to the worty and honey aroma of AFB was determined by sensory assessment of the recombinate in a beer-like matrix with omission tests. The role of 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone in AFB aroma was reported for the first time. The outcomes from this study are of relevance for the brewing industry to design strategies for the reduction of the wortiness of AFB

Orthonasal and retronasal detection thresholds of 26 aroma compounds in a model alcohol-free beer: effect of threshold calculation method

Detection thresholds are used routinely to determine the odour-active compounds in foods. The composition of a food matrix, such as hydrophobicity or solids content, has an impact on the release of flavour compounds, and thus on thresholds. In the case of beer, thresholds determined in alcoholic beer may not be the same for alcohol-free beer (AFB). Therefore, the aim of this study was to determine detection thresholds for aroma compounds typically found in beer within a model AFB. The model was designed to match the sugar concentration and pH of an AFB brewed by a cold contact process. Thresholds were measured using a 3-AFC procedure and calculated using either Best Estimate Threshold (BET) method or by logistic regression. Moreover, an algorithm for the removal of false positives was applied to adjust the assessors’ raw responses. Retronasal thresholds were generally lower than orthonasal. Those calculated by BET were significantly higher (p < 0.05) than those from logistic regression, and removal of false positives also produced significantly higher thresholds than those from raw data. The use of logistic regression has the advantage of providing the mathematical model describing the behaviour of the group. The results from this study can be used to better understand the role of flavour compounds in AFB and the effect of the calculation method to prevent under- or overestimated results

Sur les origines et cinétique de formation des arômes à moût de bière dans la bière sans alcool

The interest of consumers towards alcohol-free beer (AFB) has increased over the last few years due to several motivations. However, some of them, such as those brewed by cold contact fermentation (CCF) show a characteristic aroma reminiscent of wort or malt, lacking the appreciated fruity flavour of their alcoholic counterparts. From the current literature, the Strecker aldehydes methional, 2- and 3-methylbutanal are responsible for this aroma. The aim of this PhD project was to identify the role of odour-active compounds in AFB and their contribution to the worty character, as well as to study the formation kinetics of them during malt kilning. By means of the sensomic approach, five key aroma compounds were identified, among 27 odour-active compounds. These were methional (boiled potato-like aroma), 3-methylbutanal (cocoa-like), (E)-β-damascenone (apple, jam-like), 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone (curry, spicy-like), and phenylacetaldehyde (floral, honey-like).As a part of the sensomic method, perception thresholds of the odour-active compounds were determined in an AFB-like matrix. Differences were observed between our threshold values, both ortho- and retronasal, and the values from the literature in water and ethanol/water mixtures. Moreover, the calculation method employed (best estimate threshold BET or logistic regression) and the presence of false positives had a significant impact on the final results.In the next part of the project, the formation of (E)-β-damascenone and Strecker aldehydes during malt kilning (isothermal curing stage at 65, 78 or 90 °C) was investigated. The former increased over time in malts kilned at 78 and 90 °C, whilst at 65 °C the trend was not very clear. During mashing and wort boiling, the amount of (E)-β-damascenone was affected by a compromise between formation and degradation/evaporation.The formation of five Strecker aldehydes (the four mentioned above and 2-methylpropanal) was monitored during the curing stage of malt kilning too. These compounds are formed during thermal processes by the Maillard reaction between reducing sugars and amino acids. Multi-response kinetic modelling was used to fit the analytical results to a mechanistic mathematical model. The model developed showed the importance of the formation of two intermediate compounds in the reaction of glucose and amino acids. The first group of intermediates was Amadori rearrangement products (ARP), whereas the second was a pool of short chain dicarbonyls, such as glyoxal and methylglyoxal, that were not determined analytically. The results from the kinetic parameters demonstrated the high sensitivity of the degradation of ARP to changes in temperature because of its high activation energy.The outcomes from this PhD may have a great importance for brewers and brewing scientists. The understanding of the role of flavour compounds in AFB is the starting point to design mitigation strategies for the formation of worty off-flavours and thus improve the beer’s organoleptic characteristics and consumer acceptability.TRANSLAT

Flavour formation in foods

Maste

Fermented meat sausages and the challenge of their plant-based alternatives: A comparative review on aroma-related aspects

International audienceTraditional fermented meat sausages are produced around the world due to their convenience and sensory characteristics which are responsible for their high acceptability. They constitute a cultural heritage as shown bythe high diversity of products around the world. Recent trends are addressing issues regarding innovation in their formulation by reduction of salt, fat and additives (curing salts). However, the current trend towards a reductionin the consumption of meat has produced an increase in the formulation of meat product analogues. This trend is the main focus of producers to offer new attractive products to consumers even though the aroma profile oftraditional fermented meat sausages is not reached. In this manuscript, we review and discuss the chemistry of aroma formation in traditional fermented meat sausages in contrast to the potential of plant-based ingredientsused in meat analogues

Understanding odour thresholds: A Quantitative Structure-Property Relationship study of the role of the molecular structure

International audienceWithin the huge variety of aroma compounds identified, there are some to which humans are more sensitive than others [1]. This characteristic is usually associated with the molecule's detection threshold (DT). However, the relationship between a molecule's structure and its DT has not a straightforward answer. The understanding of odour perception requires being able to link the molecular properties of aroma compounds to their DT values. In that way, the Quantitative Structure-Properties Relationship (QSPR) approach is especially appropriate. Several studies have proposed models that relate DT and some structural features, such as the molecule's size and the distribution of positive charges, but this has been done essentially in sets of alcohols or pyrazines [2]. In this context, the aim of this work was to understand the role of the chemical structure of aroma compounds by means of a QSPR model that included a vast variety of chemical functions. In this study, we have collected from the literature the orthonasal DT values in water of 407 molecules belonging to a variety of chemical families representing the diversity of odour molecules commonly found in foods and beverages: alcohols, aldehydes, pyrazines, sulphides, among many others. Then, we have used the Biovia Discovery Studio package (Dassault Systèmes, San Diego, CA, USA) to calculate the values of 106 molecular descriptors. The original set was split into a training set (327 molecules) and a test set (80 molecules). Several QSPR models were generated using Genetic Functional Analysis (GFA) being the descriptors as independent variables and ln DT as the dependent variable. The optimisation was done by maximisation of the regression coefficient r². The best models involved at least 5 terms (r² 0.46, RMS Residual Error 3.09, LOF 37.8, F 68.5, p-value 1.254.10-51 a=0.05). By increasing to 6 terms allowed to improve the quality of the model (r² 0.50, RMS Residual Error 2.97, LOF 34.9, F 67.9, p-value 5.565.10-58 a=0.05). Four variables that encode the role of hydrophobic features of the molecules were found in both models: ES_Count_dsCH (number of CH methine groups), Jurs_RASA (relative apolar surface areas), Molecular_Weight, and V_DIST_equ (topological descriptor related to the environment of the covalent linkages). Besides, the descriptors encoding the negative charges of the molecules differed depending on the model: Dipole_mag was found to have a contribution in the 5-variable model, whereas ES_Count_ssO (number of non-carbonyl oxygens) and Jurs_RNCS (relative negatively charged surface areas) were involved in the 6-variable model. The analysis of the standardised coefficients put forward the role of the skeleton of the molecules (V_DIST_equ, positive contribution), which partially counterbalanced the global negative contribution of the Molecular_Weight. In conclusion, we have developed QSPR models that explained the contribution of different molecular characteristics to DT in water for a set of more than 400 molecules. These models will help understand odour perception and predict orthonasal DT to a certain degree. 1. Keller A et al. BMC Neurosci., 2016, 17, 55. 2. Edwards PA et al. Chem. Senses, 1991, 16(5),447-465

Characterisation of the key aroma compounds in alcohol free beer base by aroma extract dilution analysis

International audienceThe pleasant fruity flavour of lager beers is one of the most appreciated fea-tures of these beverages, whereas alcohol-free beers (AFB) also exhibit a flavour reminiscent of wort. Even though several studies have been carried out to charac-terise the key odorants in different alcoholic beers, there are no similar works for AFB. Hence, the aim of this research is to identify the compounds contributing to the characteristic aroma of AFB. In this work, the volatile fraction of an AFB-base (without added flavourings) was isolated using solvent assisted flavour evapora-tion (SAFE) and analysed by GC-MS and GC-Olfactometry. Twenty-three odour regions showed odour activity in GC-O experiments, amongst which the most po-tent were methional, phenylacetaldehyde, 2-methoxyphenol, β-damascenone, 2-phenylacetic acid, 2-phenylethanol, and 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone. The presence of these compounds plays a crucial role in AFB aroma

Quantification of odour active compounds and calculation of their orthonasal and retronasal detection thresholds in alcohol-free beer

International audienceThe low alcohol content in alcohol-free beers (AFB), i.e. below 0.05% v/v ethanol in EU countries, is not the only difference when compared to Lager beers. The pleasant fruity flavour of these beers is one of the most appreciated features, whereas AFBs brewed by cold contact fermentation (CCF) process exhibit a flavour reminiscent of wort and high amount of non-fermented sugars. These differences could alter the release properties of an AFB compared to alcoholic beers, thus affecting their perception threshold. In a previous part of this study, 24 odour regions were identified in SAFE and HS-SPME extracts. Thus, the aim of this study was to determine orthonasal and retronasal detection thresholds of these compounds in a model AFB-CCF and obtain their odour activity values (OAV) in a reference AFB-CCF. The model AFB-CCF was composed of a mixture of mono-, di-, and trisaccharides in carbonated water. Six concentrations of each compound in ascending order were sniffed and tasted by 12 or 24 panellists. The thresholds were calculated by either the standard BET method or logistic regression, and an algorithm for the removal of false positives was also utilised. The results showed significant differences between detection thresholds calculated by using the different methods, thresholds from BET method being always higher than those from logistic regression. The removal of false positives increased the threshold values as well as improved the goodness of fit of the data to the logistic function. Thresholds calculated by logistic regression with the false positives removed were used for the calculation of OAVs. Once the 24 aroma compounds were quantified by a range of analytical techniques, the OAVs showed that the most odour active compound was methional (concentration=85 μg/L, orthonasal detection threshold=0.47 μg/L, OAV=181), followed by 3-methylbutanal (38 μg/L, 0.61 μg/L, 62), phenylacetaldehyde (160 μg/L, 5.4 μg/L, 30), acetaldehyde (1,200 μg/L, 46 μg/L, 26), 2-phenylethanol (20,700 μg/L, 1,880 μg/L, 11), methylpropanal (24 μg/L, 4.3 μg/L, 5.6), and Z-4-heptenal (0.063 μg/L, 0.016 μg/L, 3.9). For the first time, the contribution of flavour compounds to the overall aroma of AFB-CCF has been decoded. The outcomes from this study may be of great relevance for the brewing industry for the reduction of the wortiness of AFBs

Characterisation of the key aroma compounds in alcohol free beer base by aroma extract dilution analysis

International audienceThe pleasant fruity flavour of lager beers is one of the most appreciated fea-tures of these beverages, whereas alcohol-free beers (AFB) also exhibit a flavour reminiscent of wort. Even though several studies have been carried out to charac-terise the key odorants in different alcoholic beers, there are no similar works for AFB. Hence, the aim of this research is to identify the compounds contributing to the characteristic aroma of AFB. In this work, the volatile fraction of an AFB-base (without added flavourings) was isolated using solvent assisted flavour evapora-tion (SAFE) and analysed by GC-MS and GC-Olfactometry. Twenty-three odour regions showed odour activity in GC-O experiments, amongst which the most po-tent were methional, phenylacetaldehyde, 2-methoxyphenol, β-damascenone, 2-phenylacetic acid, 2-phenylethanol, and 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone. The presence of these compounds plays a crucial role in AFB aroma