batfishdog37

Recipes 

I have heard that some malts work better when an acid rest is performed. Which malts, if any, would require this?

Piotr

Recipes 

I don't think there are any. Only the weizen beer can benefit from a rest in low temperaure (40-44C), I call this ferulic rest, but some call it (incorrectly) acid rest

ClaudiusB

Recipes 

I mash in at the acid rest temp (95°-98°F) for two reasons.
1. To adjust mash pH with Phosphoric acid to the required value without
rushing.
Very little conversion takes place.
I don't depend on the Phytase enzymes to lower the pH, it can take
several hours to lower the mash pH.
2. Enzyme preparation, prepares the enzymes for the hard work ahead.
Resting the mash at this temp for 30 min. improves yield regardless of base
malts used.

Ferulic acid rest is different than the acid rest (temp is different).
The ferulic acid brings out more of the phenolic character (clove) of Weizenbiers during fermentation by converting it to 4VG.

The temp I use is around 113°F.

Cheers,
ClaudiusB

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mux

Recipes 

Resurrected!
I was thinking of this, I did a RIS and I think that my pH was off due to the dark malts. I think if I mash in at 115- 120 and adjust the pH I will be able to fix it before any enzymatic conversion takes place. Any one else do this?

mjohnson

Recipes 

My understanding is that when pH is off due to dark malts, its usually means the mash is too acidic (low pH). If you suspect this is what is happening to your RIS, then an acid rest would be attempting to lower it further - which might not be what you want.

I'm no expert, though. I just play one on the internet.

Newbeerguy

Recipes 

115-120 maybe a tad too hot for the acid rest. Actually some protien rests are conducted at 122. I use 97-100 degrees for my acid rests.

erikpete18

Recipes 

I thought this was the case as well, that the acid rest was more to lower the pH into a good range due to higher alkalinity levels in water. If you're trying to raise the pH in your RIS mash, you can toss some gypsum into the liquor to bring it up a little higher. You could also leave the darkest malts out of the mash for 45 minutes and just toss them in at the end to get all the dark goodness out of them, but after most of the stuff has converted.

downpantera

Recipes 

Gypsum will lower your mash pH, not raise it. To raise the pH, use baking soda or chalk. You need very little baking soda, say ~ 1 gram to go up by 0.1, depending on thickness. You need a whole lot more chalk, around 3 - 5 grams.

erikpete18

Recipes 

Ha, crap, that's what I get for trying to use the common name. Yes, chalk (CaCO3) or baking soda (NaHCO3) is what you want, not gypsum (CaSO4). Its the carbonate ion (CO3) that will help to raise the pH. I've not used baking soda, but I know with chalk that it doesn't like to dissolve very well. Throwing it into the mash itself (instead of the liquor) will help to dissolve more of it since the mash is acidic, but you'll still have to give it 5-10 min to dissolve well and stabilize, then you can check the pH.