Note: all pH measurements referenced in the below post are room temperature measurements.
In How to Brew, Palmer states that the goal is to hit a mash pH of between 5.4 and 5.8.
However, I've read a lot of posts on this forum where people state their target mash pH is 5.3. I've also read some posts where it has been posited that a mash pH higher than 5.6 can cause problems - regardless of the style of beer being brewed.
Has there been a recent shift in thought concerning optimal mash pH?