The impact of sulfites on making sauergut, and a few other interesting tidbits

[Techbrau]

A while back, I experimented with making some sauergut cultures a few different ways. One of the interesting phenomena that I discovered was the fact that a LoDO wort made with sulfite seemed to slow the initial growth of the LAB, compared to a LoDO wort made with ascorbic acid. Here's some data:

Both worts:
9 plato OG, cooled to ~117 F
Filled to the brim in a mason jar
pH manually dropped to 4.5 with 10 g/l acid malt
inoculated with 10 g/l pilsner malt

I incubated the sauergut in a sous vide water bath, and took pH measurements every so often over a 24 hour period:

pH measurements for the ascorbic batch:
0 hours: 4.5
3 hours: 4.0
6.5 hours: 3.8
24 hours: 3.5

pH measurements for the SMB batch:
0 hours: 4.5
2.5 hours: 4.5
3.5 hours: 4.5
5 hours: 4.5
17 hours: 3.6
24 hours: 3.5

I found it interesting that the SMB wort seemed to introduce a lag phase for the LAB, but after 24h the end result was the same. I prefer to use SMB over AA, though, because anecdotally I think it works better.

Once a mother culture is made, however, refreshing it with fresh wort from a brew seems to restart the souring process immediately (evidenced by CO2 production by the heterofermentative LAB after 1-2 hours), even when the wort contains sulfites.

A few more interesting tidbits:

Sauergut inoculated with Weyermann acidulated malt only never soured. After I tossed some pilsner malt in, it soured. Makes me think that Weyermann acid malt doesn't actually have any live bacteria on it. I'm not sure about other brands.

Pinnacle Nutrition brand probiotic pills (supposedly containing 4 different strains of lactic acid bacteria) didn't sour the wort at all in the 4 or 5 times I tried using them, even when throwing 4 pills into ~1 liter of wort (each pill supposedly contains on the order of 20 billion live cells).

WLP677 (lacto d) worked fine for me in multiple attempts, but seems to prefer an incubation temperature closer to 110 F. However, I see better results using raw pilsner malt to inoculate, and it's a lot cheaper too.

[Owenbräu]

Nice write up. Since the sauermalt doesn't seems to be of any benefit from a live culture standpoint, what about simply dropping the pH initially with AA instead? Then you can utilize both AA and SMB. Citric acid should work well also, and is the preferred acid of many sour beer brewers.


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[Techbrau]

The more I read about ascorbic acid, the less I want to use it. Every paper I've read so far describes the tendency of ascorbic to become a ticking time bomb in terms of catalyzing staling down the road. That combined with the fact that as an antioxidant, it's many times less effective than SMB.

I could see using citric acid to drop the pH to 4.5. The amount of acid required to drop from 5.2 to 4.5 is such a small fraction of the total acid produced during the lactic acid fermentation that it probably doesn't make a huge difference what acid is used. The main reason I drop to 4.5 is to give the LAB a favorable environment to live in, and prevent the growth of anything nasty before the LAB get a chance to really drop the pH.

Citric acid is also supposedly a decent antioxidant, but I don't know whether or not it goes turncoat down the road like ascorbic.

[Owenbräu]

I've seen the same thing in the literature. Ascorbic seems to be several orders of magnitude less effective at scavenging O than SMB. Still, some enzymes are designed to utilize it for scavenging and my guess is a little AA adds to the complexity of SG, so I haven't ruled out its use completely.


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[Big Monk]

[Techbrau]

[Weizenberg]

[Owenbräu]

It would be interesting to see how much AA comes into the wort from the malt itself. I would surmise that malt likely has enough AA to properly supply its own enzymes.


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[Weizenberg]

It would be interesting indeed. Have you got access to any facilities that would allow for the necessary equipment to measure this?

To be clear: The context in which Narziss mentioned AA was as anti-oxidant on bottling. His warning was that it can eventually lead to detrimental effects. I can look it up again if need be.

[Owenbräu]

Not at the moment, I do not.

That would be great if you would. I'm inclined to agree that the double edge sword of AA may not be worthwhile. I am convinced it has no place in my beers post-mash, but while enzymes are active I believe it may still prove beneficial. That's why these all-in-one products don't measure up, bc you cannot use the same product for all phases, nor styles.