Yeast Metabolism

[brwmistr]

Can someone explain what goes on when the yeast break the sugar bonds? I see in my fermenter slow ferment and vigorous and have always wondered why the vigorous one looks like its boiling inside.

 

[ColoHox]

The yeast are doing the same thing, regardless of the outside appearance of the fermenter. The boiling action is because of the CO2 release as part of the sugar metabolism. The CO2 wants to rise, and it usually pulls chunks of yeast and trub up with it. After that CO2 bubbles out of your airlock, the chunks of yeast and trub fall back to the bottom.

 

[brwmistr]

Very nice diagram now I can "see" whats going on inside. Thanks

 

[ajdelange]

That diagram is extremely simplified. For more detail see http://en.wikipedia.org/wiki/Glycolysis. Be sure to scroll all the way down to the bottom of the page in order to see the whole shooting match diagrammed. You only need to go as far as pyruvic acid. In fermentation that does not enter the TCA cycle but is simply decarboxylated (that's the step where the CO2 is evolved) and the resulting acetaldehyde reduced to ethanol.