Mash/Boil

[RMitch]

If mashing above a certain temperature is bad, and produces unfermentables...what is the point of the boil? Will this not also produce/transform the wort into unfermentables?

 

[aggiejay06]

The grain isn't in the pot while you're boiling...too high temperatures during your mash will extract undesirable tannins and possibly denature your amylase enzymes (depending on how high you go), making the conversion of starch to sugar impossible. You don't have to worry about that at the boil because the grain is gone and you already have your sugars.

 

[Yooper]

Mashing is done to convert the starch in the grain into fermentable sugars. When that is done, the grain is "rinsed" to get out as many as possible. That liquid is wort.

Wort is boiled to kill bacteria, isomerize the hops oils (which only happens when the wort is boiling), and to reduce the volume.