[Pi]

Doing a Boh pils today. Used .4 lb acid malt. Is a ph of 5.0 too low for the style, and is there any way to correct this?

[kramerog]

Baking soda is something that you probably have on hand to raise pH. 

[Pi]

Just getting to Beta rest temp now. Too late to bother adding? If not how much should I add?

[BrodyR]

I'd add a bit now anyway. If you have Brun Water can try to estimate the amount. If not I would start small, take a reading, and adjust if needed.

[kramerog]

Just getting to Beta rest temp now. Too late to bother adding? If not how much should I add?

Beta-amylase likes a lower pH, according to Wikipedia, so conducting this part of mash at pH of 5.0 is fine.  The lower pH may reduce your hot break during the boil.

[mabrungard]

in my experience, low mashing pH results in reduced body and mouthfeel. At lower pH, there is likely some degradation of the poly-saccharides or proteins that would typically exist in wort. No data, just my own perceptions of the end results.

It is probably too late to correct that effect via an alkali addition. The only thing that would occur is the wort pH is higher and the resulting beer pH might be slightly higher than if you didn't do anything.

It will still be beer, either way.

[blair.streit]

in my experience, low mashing pH results in reduced body and mouthfeel. At lower pH, there is likely some degradation of the poly-saccharides or proteins that would typically exist in wort. No data, just my own perceptions of the end results.

It is probably too late to correct that effect via an alkali addition. The only thing that would occur is the wort pH is higher and the resulting beer pH might be slightly higher than if you didn't do anything.

It will still be beer, either way.

I've had similar experience. A few months ago while making an Oktoberfest I intended to add half my acid to the mash and half to the sparge water (usually I treat all the liquor at once). I was not paying attention (talking to someone) and made the mistake of doubling up. I ended up with a mash pH around 5 rather than the intended 5.3.

The beer did come out a bit thin in terms of moutfeel (and may be a bit muted in terms of flavor). It was still plenty drinkable. It probably would have been a good candidate for an experiment with freeze concentration, but we managed to drink it all before I ever got around to that.