Forgot the baking soda

[Sadu]

I brewed a 1.097 RIS on the weekend and was too busy chatting with my brew assistant that we forgot to add the campden and baking soda. Was meant to be 8g of baking soda in a 5g batch to bring the mash into line.

I'm not going to stress about it since my last unadjusted RIS was excellent but is it worth adding the baking soda to the fermentor to bring up the beer pH?

 

[JonM]

Not much to do about it now, but how did you calculate 8 grams? That sounds like quite a lot.

 

[ajdelange]

8 grams seems like an awful lot of bicarbonate for a 5 gal batch. Eight grams of bicarb neutralizes 95 mEq of acid. In a typical RIS recipe (i.e. one I grabbed off the net) the black malts/barley amount to about 13% of the grist. Usually if the total of these is kept under about 20% (depending, of course, on the particular black grains and the base malt) no alkali is required. Indeed the particular recipe I tried gives an estimated mash pH of 5.57 without any bicarbonate. Adding 8 grams of NaHCO3 to this mash raises the estimated pH to 5.75.

So it seems likely that you are going to be OK. Do not add bicarb to the fermenting or finished beer. This will divert the yeast from making stout to making acid.

 

[Sadu]

Cheers guys.

The 8 grams I calculated with Brunwater. I have 13% roasted malts like you say and 7% crystal, MO as the base malt. My water has 36ppm bicarbonate so not much there to soak up the pH drop from the roast malts and the CaCl / Gypsum got added to the kettle rather than the mash.

Without the Baking Soda Brunwater says pH 4.9

That said the last RIS I made, without any mash adjustment, came out with plenty of the right flavours so I figure I'll be fine.

 

[ajdelange]

Bru'n water tends to get a little carried away on the acidities of dark malt. If I shift what I assumed around to match your percentages better and go to Crisp MO which is considerably more acidic than Muntons (which I used in the calculations from yesterday), ignore the alkalinity of the water and leave out the bicarbonate I get an estimate of 5.47. The 36 ppm bicarbonate would only increase that by 0.02 pH but the 8 grams would shift to 5.66. Any of these would be OK. The 5.66 might be considered highish but would probably be OK.

The message here should really be that mash pH predictions can be quite tricky depending on how you model the malts i.e. whether you take a stab at malt properties from their colors or descriptions or use actual measurements on malts (best) or, more realistically, use measurement data from malts you believe to closely match the malts you are using. The solution is to use calculations only as a rough guideline and verify with pH measurements made on test or actual mashes.