There is a widely held view that warmer mash temperatures – ie 67 degrees plus, make for a maltier beer. You will often read this in homebrewing books and in online discussions. It is wrong. It doesn’t matter how many times you read it, it is still wrong.
Don’t take my word for it. The following is a quote from Dr Chris White and Jamil Zainasheff
One thing many brewers have been led to believe is that higher mash temperatures result in “maltier” beers. By this they mean that the beer has more malt sweetness. Higher mash temperatures do not develop more malt character or flavor, nor does it really result in much sweetness.
Yeast: The Practical Guide to Beer Fermentation, Brewers Publications, Boulder Colorado 2010, page 70