Lesson 3 - Fermentation Principles SAQ

*Define the following terms:

a)    Attenuation gravity

b)    Wort fermentability

c)    Original gravity

d)    High gravity brewing

Response:

a)    Attenuation gravity is the final gravity reached in fermentation when all of the fermentable sugar has been consumed by the yeast.

b)    Wort fermentability describes how much fermentable sugar a wort contains. It is expressed as a percentage equal to the starting gravity minus the final gravity divided by the starting gravity multiplied by 100.

c)    Original gravity is the starting gravity. It is given this name because in many circumstances it is not possible to measure it directly. This is because many fermentations are pitched before all the wort has been added and fermentation may well have started before wort transfer is finished. However, if you measure the gravity and alcohol concentration at any point in fermentation you can calculate how much extract has been used and therefore determine what the initial gravity must have been. This is the original gravity.

d)    High gravity brewing is the practice of making and fermenting a very concentrated wort to produce a highly alcoholic beer. After conditioning and either before or immediately after filtration, the concentrated beer is diluted to the strength at which it will be sold.

The reasons for doing this are to increase the productivity of the brewery with a minimum of capital spending. If the wort is doubled in concentration the result will be almost a doubling of beer yield per fermentation. This is not quite true since the cycle time will also increase. Providing the brewhouse can make the concentrated wort it has become a very popular strategy for increasing brewery productivity with minimum spend.