| Beer flavour is a very complex subject. Over 800 compounds have been
identified that contribute to the characteristic flavour of beer. The main flavour
characteristics are the bitter taste derived primarily from the hops, an alcoholic note
from ethanol and a carbonation mouthfeel from CO2. Secondary flavour notes
include fruity estery flavours, alcoholic notes from higher alcohols and various sulphur
components. However, most of the flavour compounds are present in very small quantities
(below their individual taste threshold) and act synergistically to provide the balanced
and refreshing taste of good beer. Occasionally undesirable flavour components may appear,
giving the beer various off-flavours. The flavour components and their precursors originate from the raw materials, namely malt, adjuncts, water or hops, or are produced by the yeast during fermentation of the wort. Consequently, the selection of raw materials and/or yeast strain has great impact on the flavour. However, the flavour is also influenced by technological factors which affect the composition of the wort, and the conditions during fermentation, maturation, filtration and bottling. Flavour assessment is therefore very important in quality control of beer. One of the most important tools is the sensory analysis by a panel of well-trained tasters. To enable a precise description of a beer sample a common terminology has been elaborated. Each flavour impression is quantified on a scale of 0-10. In recent years the methods for chemical analysis have improved dramatically. It is now possible to monitor the concentration of many flavour active components. Quantification of higher alcohols and esters by headspace analysis using a gas chromatograph is now a routine analysis in many breweries. At the Carlsberg Research Laboratory analyses for a wide range of yeast secondary fermentation products have been established. These analyses are used to study the effect of different raw materials, yeast strains or brewing processes on the profile of flavour components in the beer. Beer is a very fragile liquid which will deteriorate rapidly unless stored under cold and dark conditions. The stale "cardboard" flavour which may appear upon storage is mainly due to very small amounts of trans-2-nonenal, a lipid degradation product formed during malting and wort production. At the Carlsberg Research Laboratory the brewing process - from malting to beer pasteurisation - is examined to pinpoint the critical steps of lipid oxidation. |
|
