flavour
The tasting is an very important procedure before beer leaves the brewery and reaches the consumer. The consumer does no chemical investigations on the beer. The only things that the consumer is interested in are taste, smell, colour, turbidity, foam stability and a certain shelf life. The chemical investigations that are done in the brewery are necessary to guarantee for example the shelf life, but there are a lot of chemical groups that can cause off flavours and unwanted smells. Because of this, it is indispensable to carry out a tasting before beer leaves the brewery
The mechanism of stale flavour development in beer and ways to inhibit staling have long been of interest for the brewer. It is well known, that levels of oxygen in packed beer and shelf storage conditions are important factors in stale flavor development. It is also generally agreed that oxygen pickup and overall reducing potential through out the brewing process, including those Steps prior fermentation, may have a cumulative effect on flavor stability. There are naturally several substances in beer, that have a high reducing potential, to contribute to a better taste stability by reducing the occurrence of stale flavor. They can act by decreasing molecular oxygen levels, scavenging chain-initiating and chainpropagating
free radicals, chelating metals, decomposing peroxides, or changing of volatile aldehyds into non volatile substances. Sulphite, ascorbic acid, superoxiddismutase, phenols and many other compounds will contribute to a good flavor stability.
Phenolic compounds are of considerable significance in brewing. Its most important
aspect is in relation to haze formation. Simple acids are part of the numerous
substances and more highly condensed phenols with protein precipitating and reducing effect. These substances influence colour, foam, stability, flavour and taste. The main part with nearly 80% of these substances comes from the malt, the rest from the hops. The water can also contain such connections but only in very small quantities. Hop extract contains no phenolic compounds; therefore none of these substances can reach into the wort. The use of phenol reduced barley like proanthocyanidin-free barley also leads to a clear reduction of these connections. The effects of these substances on the beer quality are known but there are discrepancies about its meaning in the positive and negative meaning. The low molecular compounds are very strong antioxidants and being able to offer protection against oxidation through it. This has to be judged to be positive. Other groups are directly or indirectly involved in the taste behaviour. This can also be positive and negative. The most important property is their ability to build hydrogen bridges with proteins or with other phenols what can be lead to haze formations.
The taste and the flavour are determining for the quality of any alcoholic beverage. A wide range of aromatic components are responsible for their individual character. Vicinale dicetones belong to the family of by-products of keto groups neighbouring one another (=vicinale). 2,3-Butandione "diacetyl" and 2,3-pentadione are representative of this group. They give an unpleasant taste and flavour to the beer at concentrations above the taste threshold, therefore this effect is called "off-flavour". It distinguishes itself through a sweet and butter aroma. Like character, which is mainly caused of Diacetyl, because its taste threshold is Iower 0,07-0,1 mg/ml than the threshold of Pentandione which can be recognized only at a concentration of 1,5 mg/ml.