Chemistry of alcoholic beverages

Beer Flavor and Beer Defects.
The taste and odor profile of a beer, including possible aroma defects, can be described in detail with the help of 44 terms grouped into 14 general terms. Apart from a great variety of terms for odor notes, the terms bitter, salty, metallic, and alkaline are used only for taste and the terms sour, sweet, “body” etc. are applied to both taste as well as odor. Nine of the terms describe the most important odor and taste characteristics of a good beer. They are also suitable for the differentiation of different types of beer. Foaming is an important criterion of the taste of beer. A distinction is made between foam volume (produced by the content of carbon dioxide), foam density, and especially foam stability (caused by protein degradation products, bitter hop compounds, and pentosans). Lower fatty acids that are present in beer bouquet act as de 9-foamers. Beer defects detract from the odor and taste and are caused by improper production and storage. An example of a taste defect is the harsh, hard, bitter taste produced by the oxidation of polyphenols and some hop constituents. A flat taste, as already mentioned, comes from a low content of carbon dioxide. Diacetyl and ethanal in concentrations greater than 0.13 mg/l and 25 mg/l respectively, produce a taste defect. Acceleration of fermentation caused, e. g., by intensive stirring of the wort, raises the content of diacetyl and higher alcohols in the beer and lowers the content of esters and acids. On the whole, the aroma is negatively influenced. Higher concentrations of ethanal can arise, e. g., at higher fermentation temperatures and higher yeast concentrations. Beer is very sensitive to light and oxidation. The “light” taste is due to the formation of 3-methyl- 2-buten-l-thiol. This substance becomes unpleasantly noticeable at concentrations higher than 0.3 µg/l. It is one of the characteristic aroma substances below this concentration
Wine
Wine is a beverage obtained by full or partial alcoholic fermentation of fresh, crushed grapes or grape juice (must). The woody vine grape has thrived in the Mediterranean region since ancient times and Italy, France and Spain are still among the leading wine-producing countries in the world. Other major producers are USA, Argentina, Chile, Germany and South Africa. This provides data on wine production and consumption in some countries.
The wines are considered rather ordinary, with less character and a more obtrusive flavor than the parent plants. Grape cultivars providing top quality white wines are:
• Riesling – native to Germany; a hardy cultivar grown in the Pfalz (Rhine Palatinate) and along the Mosel (Moselle), Rhine and Nahe rivers.
• Traminer – cultivated extensively in Alsace, Baden and Pfalz, and in Austria.
• Rulaender (grey burgundy, Pinot gris) – from Alsace and Burgundy regions in the Kaiserstuhl district, and from Hungary.
• Kerner – an early ripening cultivar, which comes close to the balance of Riesling.
• Semillon Blanc – together with Sauvignon and sometimes with Muscatel, provides Sauternes from the Bordeaux region.
• Sauvignon – used for Sauternes, and processed into its own types of wine, such as in the Loire region.
• White Burgundy (Pinot blanc) – yields the white wines from Burgundy (Chablis, Meursault, Puligny-Montrachet).
• Chardonnay – related to white burgundy, cultivated for example in Champagne.
• Auxerrois – also related to white burgundy. Grape cultivars providing good white wines are:
• Muscatel and Muscat-Ottonel – cultivars with an exceptionally rich bouquet.
• Furmint – the grape cultivar of Hungarian Tokay wines.