Mash - Affects of Temperature and Time?

How do mash temperatures and mash times affect the wort?

High vs low temperature?

Does extending the mash time help or hurt anything?

Thanks.

Low temps = more fermentables, high temps = more dextrin (body)

Mashing is complete in about 20-30 minutes, the remainder of the mashing time is for extracting color and flavors from the grain...you don't gain anything by extending past 90 minutes.

There are two enzymes at work, one which breaks the sugar chains in half, (again and again) and one which breaks the chains by taking one molecule from each end of the sugar chain at a time.

One of these works best in the 148F range, the other in the 158F range.
To get both of these enzymes working, we often mash around 154F. 158F will leave some of those chains behind, leaving more body/mouthfeel. 148F will convert more of those chains all the way to single molecules for the yeast, resulting in more conversion to alcohol, but a thin, watery mouthfeel to your beer.

Time is important because the enzymes need time to find all the molecules and work them - 10 minutes won't do it. Generally, 60 minutes is a good all-around time for a mash. Longer won't necessarily yield more maltose.

Great info. Thanks!

if you want more detailed info read up here:
http://braukaiser.com/wiki/index.php?title=Starch_Conversion