Some questions about boiling the wort...

[Elysium]

I have been reading the importance of boiling on the forum......I understand most parts, but this:

"-To drive off unwanted volatile compounds;
-To coagulate unwanted proteins;"

Can anyone tell me what the chemistry is behind these 2 things?

 

[Monster Mash]

The volatile compounds are mainly DMS which gives your beer a cooked corn flavor. It gets removed with the steam as it boils which is why you do not want a lid on your pot.

The proteins are coagulated by hot and cold breaks, as it is boiling you will start to see what looks like egg drop soup, that is protein. When you transfer to your fermenter it gets left behind in the pot. It is defined as the insoluble precipitate that results from protein coagulation and simpler nitrogenous constituents that interact with carbohydrates and polyphenols.

 

[daksin]

I have been reading the importance of boiling on the forum......I understand most parts, but this:

"-To drive off unwanted volatile compounds;
-To coagulate unwanted proteins;"

Can anyone tell me what the chemistry is behind these 2 things?

The chemistry is actually fairly simple: Volatile compounds, by definition, evaporate easily. The best way to get them to do that is by heating them up. For boiling for a long time, you ensure that everything you don't want has evaporated out of the solution.

Proteins are long complex chains of amino acids, and their function (and solubility) is dependent primarily on the shape they take when folded up. Heat breaks down the bonds that holds them in their shape and exposes all sorts of parts of the chain that don't like water very much, and attract other denatured (unfolded) proteins, so they tangle up together and become insoluble, falling out of solution as the hot and cold breaks.