Ramsey, Imogen
(2021)
Developing an understanding and improved sensory quality of low alcohol beer.
PhD thesis, University of Nottingham.
Abstract
The international non-alcoholic beer (NAB) market is predicted to be worth over $25bil by 2024. Consumers across the globe are limiting their alcohol consumption due to changes to healthier lifestyles and increased knowledge of long-term effects of alcohol. Research has shown however, that consumers find NABs ‘bland’, ‘disappointing’ and ‘less tasty’ than their higher alcohol counterparts. Consequently, the development of a NAB that displays similar sensory pleasure to its higher alcohol counterpart is an attractive proposition to manufacturers and consumers alike. This research therefore aimed to understand both the sensory and physicochemical role of ethanol in beers with different ethanol concentrations and within a range of commercially produced NABs, whilst also identifying the overall effect on consumer liking. Furthermore, investigations into the effect of physical dealcoholisation techniques (namely reverse osmosis) on the sensory and physicochemical properties of two different beer styles were assessed. To achieve these aims, four studies were employed.
Consumers indicated their liking and changes in temporal sensory properties for flavour, taste and mouthfeel in beers with different ethanol concentrations. No significant differences amongst samples were discovered for overall liking; however cluster analysis revealed three groups of consumers with different liking patterns. Drivers of liking/disliking were discovered for each cluster, highlighting that in relation to ethanol concentration, different negative and positive sensory drivers of preference exist for different segments of consumers. Overall, ethanol was shown to be linked to the perception of sweetness, mouthfeel/body and alcohol warming sensations by consumers. Furthermore, differences in retronasal flavour by consumers, such as increased maltiness in the 0% beer, led to investigations exploring saliva*ethanol interactions as the mechanisms, with results showing that ethanol had a subtle inhibitory effect on binding of hydrophobic compounds to -amylase. This thereby increased their headspace concentration in higher ethanol concentrations. This research provided a basis for further investigations in the reformulation of NAB.
To further explore the effect of reduction of ethanol, physicochemical and sensory differences amongst commercial NABs were reported. Different clusters of samples were found, yet specific production methods were not able to fully explain these clusters; instead other important pre and post processing methods were proposed to be the reason for this. On a broader level, grouping production methods into physical or biological techniques suggested that physical production methods produced beers with undesirable sensory characteristics, such as bitterness and astringency which were least liked by consumers. However, physical methods, in particular membrane filtration techniques, have been reported by the literature as being the most promising for producing NABs with least volatile reduction, yet few studies looking at the effect this process has on sensory properties have been conducted. Therefore, improved understanding of these techniques was gained through sensorial and physicochemical analysis by the dealcoholisation of both a lager and stout style beer using a selected membrane - reverse osmosis. This technique significantly impacted the overall quality of the beer, due to extreme losses of volatile flavour compounds which affected sensorial characteristics, identified by a trained panel. Volatile losses were proposed to be due to volatile structure, as opposed to size as proposed by the literature. Furthermore, replicate trials found decreased efficiency in running times, proposed to be due to membrane clogging, and a presence of a contamination residue within the dealcoholised beer, suggested to be the result of membrane fouling.
This research delivered valuable insights on the sensorial and analytical influence of ethanol concentration, advancing the little published data available on the impact within a beer matrix. For the first time, the in-depth assessment of commercially produced NABs revealed that advancements in technologies meant that sensory profiles can be altered by pre and post processing methods. Reverse osmosis severely impacted the sensory quality of different beer styles, showing more research is needed to improve understanding of products produced by this method. This thesis furthers understanding of both sensorial and physicochemical characteristics of NABs, providing insights for the successful development and reformulation of NABs with desirable sensory characteristics.
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