Technical focus Brewlab’s Dr Keith Thomas

What’s in your mouth as you taste a beer? Beer of course, and with all of its delicious components. What’s in your mouth after you’ve tasted a beer? Well, there’s clearly something since we can normally taste a beer for a good while afterwards. Generally, this would be termed mouthfeel but also body or aftertaste or even “harmony”. Not only does this contribute to our appreciation of a beer but also, and critically, to its drinkability. As we all know appreciating a beer can be a prolonged experience lasting perhaps up to 30 or more minutes after the last swallow. This is partly due to lingering bitterness but also the physical impacts of viscosity providing a smooth coating and, in contrast, aggressive polyphenols causing astringency. As with aroma and taste it is the brewer’s target to keep these in suitable balance according to the style or brand specification. Styles differ, of course, with dry IPA’s being the opposite of smooth, and milk stouts showing smoothness or barley wines with a rich, solid body. However, there are common faults which can override any style’s mouthfeel. An excessive astringency may result from over-sparging with untreated liquor extracting too many polyphenols. In contrast excessive residual sugars or glycerol from fermentation may give a beer that thick and syrupy finish. The major features contributing to a solid mouthfeel and palate fullness are original gravity – in effect the strength of the beer, its viscosity, total nitrogen - in effect the protein content and ß-glucan – a carbohydrate extract from the malt. In technical terms body incorporates features of compactness or fullness and richness or according to the ISO rather pompous definition “mixed experience derived from mouth sensations that relate to the physical or chemical properties of a stimulus”. Full specification is available at https://

docplayer.org/74244898-Din-en-iso-

normen-bis-dezember-2013.html if you wish to read the full detail but particular features include carbonation, astringent, drying, smooth, full, watery and mouth coating. Residual dextrin sugars are particularly important contributors to mouthfeel and experiments with spiked beers indicate that fullness increases with addition of dextrin polymers of between 16 and 88 glucose molecules without giving slimy or oversweet sensations. Selecting dextrins of this specificity is difficult on a production basis but may be helped if advanced enzyme mixtures are used.

Overall, this implies that stronger beers have a more solid mouthfeel as is generally observed. Malt varieties will contribute differently to this as will different brewing practices. More highly modified malts will have lower levels of protein while a stepped temperature mash will digest more ß-glucan and protein and so be lighter in body, particularly if a vigorous boil removes more protein. As competent brewers we should be able to control our ingredient selection and processing to achieve a target mouthfeel suitable for the style. This is perhaps most easily managed with a cereal cooker. In the absence of a temperature-controlled mash though we would need to ensure a suitable selection of ingredients and that careful control of sparging produces enough residual sugars to provide body but with limited polyphenols to prevent harsh astringency. The clue here is a suitable pH of the sparge liquor to match that for the mash. A particularly difficult challenge for mouthfeel is in producing low alcohol beers which, depending on their means of production, can have low palate fullness if produced by evaporative techniques or a high palate fullness from excess residual sugars if produced by controlled fermentation. In the former case thermal evaporation tends to produce low palate fullness and limited aroma – an incomplete beer. With controlled fermentation sweetness and wortiness dominate. In this case the balance between alcohol and body is inverted and is a clear reason for low alcohol beers to be tasted as atypical. Analysis of low alcohol beers indicates that the balance between a too thin and a too thick palate fullness depends on the proportions of low, middle and high molecular mass components – proteins, polyphenols and polysaccharides. Proteins are mostly low mass, protein-polyphenol complexes are middle mass and cell wall polysaccharides high mass. Management of your malt choice and mashing programme can control these with maltsters increasingly active in providing suitable varieties to fit requirements. Larger scale production has options of blending evaporative and fermentationcontrolled production to achieve a mid-ground or adding iso maltose as an adjustment for an ideal harmony. On a small scale, harmony is as much a product of experience and skill – attributes and characteristics increasingly prevalent in the craft brewing industry.

Managing the mouth

What do we mean by ‘aftertaste’ or ‘mouthfeel’ when it comes to tasting beer, and what qualities produce certain lingering flavours? Brewlab’s Keith Thomas takes a look…