main (primary) fermentation of must the sugar is converted into alcohol. Protein, pectin, tannins, tartrate and yeast cells settle at the bottom of the fermenter giving ’bottom mud’. The secondary fermentation stops at 12–15% (v/v) ethanol depending on the type of yeast.
Addition of sulfurous acid to the wine prior to the first racking suppress the growth of undesirable microorganisms, prevent enzymatic browning and preserve constituents that are prone to oxidation. Turbidity of wine is caused by oxidized and condensed polyphenols, proteins or multivalent metal ions. It can be eliminated with precipitation reaction or adsorption following clearing.
The main quality-determining constituents of winesare extract, ethanol, glycerol, sugar, acids and bouquet substances. The evaluation and classification of wine is accomplished with the combination of chemical analysis and sensory testing.
Ingredients of beer making or brewing are germinated barley (malt), hops, yeast and water. Hops and aroma constituents forming during fermentation are responsible for its flavor and bitter taste. Carbon dioxide content provides its refreshing effect and stability. The nutritional value depends on the unfermented solubilized extract content (carbohydrates, protein). The ethanol content ranges from 1.0 % (low fermented extract-rich beer) to 5.5% (strong beer). Most of the extract is carbohydrate (mostly dextrins) ranging from 2–3% in plain beers to 8–10% in strong beers. Among acids lactic acid, acetic acid, formic acid and succinic acid are also present in small quantities. The carbon dioxide content is ranging from 0.2% (in flat and dull beers) to 0.44% (in bottom fermented beers). Nitrogen compounds originate from raw materials and yeast. They can cause cloudiness in beer during cold storage. Some flavor substances derive from hops and pass into the beer on boiling the wort. The presence of certain odor- and taste-active substances determines the type of beer. Isohumulons, and humulenes (including oxidation products) are responsible for the bitter taste of Pilsener beers. Furaneol promote the caramel note of dark beers. The foam building properties of beer depends on the common presence of proteins, polysaccharides and bitter constituents. β-Glucans stabilize the foam owing to the increment in viscosity.
Appendix A. Appendix 1