Fermentation

The essential chemical changes which take place in the world under the influence of the yeast transform it into beer by fermentation. The quality of the yeast has been developed through successive fermentations and the brewer now has to control this process by regulating the temperature and by airating as well as rousing the world. His aim is to ensure a vigorous fermentation which will leave just the right amount of fermentable matter in the beer at racking to provide proper secondary fermentation in cask. Individual conditions are peculiar to each brewery, size and shape of fermenting vessels, even the positioning of attemperators introduce variations in the fermentation, so that different breweries may have different problems although using the same system of fermentation.

Systems of fermentation may be divided into four main classes. We deal mainly with top fermentation systems. Top fermentation systems are so-called because the yeast crop which is to be gathered and used to kitchen future fermentations is collected from the yeast thrown up into the head. The system of bottom fermentation, which is used in brewing lager beer, differs considerably in many ways and various types of yeast are used.

As for wine, during the primary fermentation the yeast cells feed on sugar and multiply producing carbon dioxide gas and alcohol. The temperature during the fermentation affects both the taste of the end product as well as the speed of fermentation. For red wines the typical temperature is from 22 to 25ºC, and for white wines – 15 - 18ºC. For every gram of sugar that is converted, about half a gram of alcohol is produced. If the sugar content of the grapes is too low to obtain the desired alcohol percentage, sugar can be added. Alcohol of more than 12% can be achieved by using yeast that can withstand high alcohol content. Some yeast can produce 18% alcohol in wine, however extra sugar is added to produce a high alcohol content.

During or after the alcoholic fermentation, a secondary, or malolactic fermentation can also take place, during which specific strains of bacteria convert malic acid into the milder lactic acid. This fermentation is often initiated by inoculation with desired bacteria.

Active Vocabulary

Fermentation – бродіння

Yeast – дріжжі

Barrel – бочка, баррель

Content – вміст

Temperature – температура

Lager beer – лагерне пиво

Attemperator – охолоджуючий пристрій

Brewery – пивоварний завод

Ferment – фермент

Positioning – розташування

Bacteria – бактерії

Acid – кислота

Taste – смак

Speed – швидкість

Vessel – резервуар, чан

End product – кінцевий продукт

Quality – якість

Cask – бочка

Alcohol – алкоголь

Primary – первинний

Specific – специфічний

System – система

Task 1

Match the end of each sentence with its end

1. The temperature during the fermentation affects both …	a) using yeast that can withstand high alcohol content.
2. Alcohol of more than 12% can be achieved by …	b) four main classes.
3. Systems of fermentation can be divided into …	c) the taste of the end product as well as the speed of fermentation.
4. The system of bottom fermentation, which is used in brewing lager beer, differs considerably in many ways and …	d) through successive fermentation.
5. The quality of the yeast has been developed …	e) various types of yeast are used.
6. For red wine the typical temperature is …	f) about half a gram of alcohol is produced.
7. For every gram of sugar that is converted …	g) from 22 to 25ºC.
8. During or after the alcoholic fermentation, …	h) 18% alcohol in wine.
9. Some yeast can produce …	i) a secondary, or malolactic fermentation can also take place.

Task 2