Technological Factors of Flavour Stability

Abstract

The flavour stability of a beer primarily depends on the oxygen content of the bottled beer, but the individual steps of wort production are of similar importance viz:-(a) preservation of reducing substances by avoidance of oxygen pick-up during mashing, lautering and wort boiling. (b) elimination of substances which are prone to react to flavour active compounds like carbonyls by good mash and wort separation procedures, (c) avoidance of an excessive exposure of the wort to heat, to limit the formation of Maillard reaction products and related substances. Existing brewhouses offer some possibilities to improve the process and thus flavour stability. For analytical control Gas Chromatography and High Performance Liquid Chromatography are excellent tools, even simple analyses help to avoid unwelcome changes in the day to day practice.Key words: Oxygen uptake, oxidation, lautering, wort turbidity, hops, fatty acids, mash and wort separation, melanoidins, wort boiling, carbonyls, N-heterocycles, colour, •HMF'-value. GeneralTogether with a well developed character, foam proper ties and biological as well as the physical-chemical stability, flavour stability is a significant quality factor for a beer. For that reason, the subject 'Flavour stability1 was the subject of a great many scientific and practical publications during the last 1 j decades. Among these, there are some surveys repre senting the relevant state of knowledge in 1974, '' 1977s and 1981.*'31 These papers have contributed brick by brick to the building of our knowledge today. Questions from the brewing industry as well as cooperation on an international basis, in particular within the EBC Biochemistry Group initiated four doctors theses which were dedicated either exclusively or partly to this subject.2'13'15-30 The result of these dissertations has already been or is being published. This publication is an attempt to correlate these results with those obtained by full scale trials to demonstrate the contribution of research in brewing technology, to the improvement of flavour stability in beer.In the discussions on flavour stability or as Dalgliesh5 proposed-on 'flavour instability' mainly the change of the aroma component of the flavour was cited. This can be traced and identified by gas chromatography and high performance liquid chromatography. But there are also changes in the taste of beer, which cannot or can hardly be identified by analysis and which nevertheless cause a notice able alteration of the body, the liveliness and the bitter taste and thus on the balance of a beer.They are attributable to changes of the state of the col loidal matter such as proteins or protein-tannin complexes, P-glucans, dcxtrinsand bitter substances. By the use of good quality raw materials and good brewing practice along with a suitable stabilisation of the beer it is easier than 10-15 years ago, to keep these alterations within certain limits. All these processes arc occurring simultaneously and thus they promote or inhibit one another. An increase of the mcl...

A New Validation of Relevant Substances for the Evaluation of Beer Aging Depending on the Employed Boiling System

“…The coefficient of variation of the analysis of aroma compounds was less than 5%. The assortment of the analyzed substances was made depending on their relevance as aging components [5][6][7][16][17][18]23,30,36,39,40,[42][43][44][45][46]48,49,[51][52][53]55,56,59,[66][67][68]71,72 and on commercial availability.…”

“…Flavor stability of beer is mainly dependent on the oxygen uptake during production, filtration and bottling 8,9,27,33,40,41,59 . In addition, thermal treatment of wort [12][13][14]47 , pH-value 17,19,21,28 , and storage conditions 4,21,24,69 have been shown to have a significant influence on flavor stability.…”

Hydrophobins, beer foaming and gushing

“…Multivalent cations improve foam stability via reversible cross-linking with hop acids and proteins (Simpson and Hughes, 1994). 5-Lipids: Sources of lipids in beer are mostly malt but also hops and yeasts producing lower molecular weight fatty acids such as C 6 or C 8 (Blum, 1969;Anness and Reed, 1985;Letters, 1992;Narziss et al, 1993). In the finished beer little amounts of lipids remain present.…”

Flavour Instability of Pale Lager Beers: Determination of Analytical Markers in Relation to Sensory Ageing

“…Typically, a decline in beer bitterness (both in quality and intensity), the development of sweet taste and the appearance of cardboard flavour are connected to flavour instability 14,44 . In particular, formation of volatile aldehyde compounds is recognised as one of the major causes of flavour deterioration upon storage.…”