Glossary

Fermentation : Fermentation is the transformation of sugars by micro-organisms. The fermentation of these sugars by yeast yields alcohol. This process takes place in big tanks, called fermentors. The secondary fermentation (refermentation) is another fermentation, but in the bottle this time. 1.Bottom fermentation. Beers made from bottom fermentation are the most widespread. They are usually pale or blonde beers, light in alcohol, with a rather neutral flavour. During the production of these beers, yeast is injected at lower temperatures (6.5 to 8.5 °C), in chilled fermentors containing the wort of the future beer. Then, when fermentation is finished, one chills the beer to 0°C. The yeast settles down at this point and the beer will go through a maturation phase before being drinkable. 2.Top fermentation beers are produced at higher temperatures, 15 to 25 °C. This gives for faster fermentation and beers with more fruity, aromatic characteristics. The quantity of yeast used is lesser than for bottom fermentation. The yeast stays at the surface of the beer during the fermentation. these beers, more typical and darker, are called porter, stout and ale in England. 3. Spontaneous fermentation is typical for certain belgian specialty beers : one referments the beer in rooms at a temperature of 16 °C, without adding yeast. Only the micro-organisms floating in the air touch the beer during this natural fermentation. When the product thus obtained, the lambic, is placed in wooden vats for refermentation for at least two years, one obtains gueuze. One can also obtain Kriek by steeping cherries in lambic. Other possibilities includes the use of raspberries, cassis... These beers are usually amber or red.