The influence of beer physical stabilisers on beer flavour stability
Novotna dos Santos, Olga
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Beer contains proteins and polyphenols that are known to be responsible for undesirable haze formation. In this work, haze forming compounds were monitored and the effects of their removal on flavour stability were examined. The main aim of this research was to confirm or deny the influence of physical stabilisation on beer flavour. Beer was made in the university pilot brewery with a pale malt to 5% ABV and 25 International Bitterness Units. Physical stabilisers commonly used in beer stability treatments (i.e., Chill Garde™, Lucilite XLC™ and TR™, Polyvinylpolypyrrolidone and tannic acid) were added to a beer at manufacturers recommended amounts (i.e., high, medium and low levels). The beer was aged up to 11 weeks. Numerous analytical examinations were undertaken including pH, alcohol, tannoid and proteins levels, foam stability, haze, total polyphenol levels, iron copper and manganese levels, electron spin resonance t150 values, bitterness, total and free SO2 levels, polyphenol species, volatile esters, higher alcohols, acetaldehyde and total vicinal diketone levels. After extensive sensory training, panellists were used to evaluate beer sensory attributes. The analytical results of flavour compounds were immediately compared to sensory testing. Sensory profiling and the ‘two out of five’ difference test were employed to evaluate beer flavour. The sensory profiles of all stabilised beers were also compared to unstabilised control using spider plots. Linear regression was used to correlate the results from analytical measurement to sensory data. Sensory differences between stabilised and unstabilised samples were not found. Neither the trained sensory panels were not capable to recognise differences using two out of five test. The effectiveness of each physical stabiliser on haze and flavour was presented and discussed. As a result of this work it can be argued that the removal of haze active polyphenols nor removal of the haze-active proteins substantially influence beer flavour. This work has gathered enough data to compare the stabilisers and decide on their effectiveness. The most effective beer stabilising agent was PVPP, it worked at the lowest dose (5g/hl) efficiently improving haze stability and yet it did not influence flavour stability. The other stabiliser presented in literature as the effective polyphenol removal agent did not remove polyphenols at low dosing level, it was only effective at high concentration, the influence on flavour was not proved either, however the use of such stabiliser would not be economic for the brewer. Interesting for the future research would be to study in detail the stabiliser Chill Garde to be able to answer why it also removes polyphenols and whether its use could replace the actual practice of breweries that is the combined stabilisation. Chill Garde removes haze active proteins but in great extent it also removes all of the haze active polyphenols. This fact was not described in literature nor in the data sheets for this products. Much of the data obtained in this work was used to track changes in flavour during ageing, no forced ageing was used, and this data was used to enrich the Dalgliesh model of beer ageing and track the changes in beer sensory during a period of 11 months.