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Home Brew Forums > Home Brewing Beer > Brew Science > Less dilution, more acid - or - more dilution, more salts?
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Old 02-02-2013, 05:45 PM   #11
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Oh, I missed the questions in post #6 above.

No, the calculations above are not correct. The bicarbonate neutralization (-bicarb) is in mg/l units. So the volume of water treated enters the calculation. For example, the 76.4 mg/l of neutralization in the first mash example required 1.8 mL to treat X gallons or 1.8/X mL/gallon. I don't know what the mash water volume was, so I inserted X.

The calculation to figure the amount of bicarbonate neutralization in the sparging water is not appropriate in this case. The way it was done above should produce the same 76.4 mg/L neutralization if the volumes of water for the mash and sparge were included in the calculations. But since sparging water is not neutralized to the same degree as mashing water, it is not appropriate to use the calculation above.

A more appropriate way to evaluate the concentration of bicarbonate neutralized is to look at the difference in the starting and ending alkalinity. Say you are at 152 ppm alkalinity as CaCO3 and you want to end up at 25 ppm. That is a reduction of 127 ppm alkalinity. 1 ppm alkalinity (as CaCO3) is equal to 1.22 ppm of bicarbonate neutralized. So the bicarbonate neutralized by the sparge acidification is 127ppm x 1.22 = 155 ppm bicarb (-155 ppm bicarb). Since lactic acid is monoprotic, that means that 155 ppm of lactate is added to the sparging water when neutralizing that much alkalinity.

To figure out the average lactate ion addition to the kettle wort, you would have to do a volume-weighted averaging of the lactate ion additions from the mash and sparge.

You are correct that the mineral additions to sparging water are not considered to further reduce the pH of the sparging water. I suppose that the phytin in the wort could still react with the Ca and Mg to produce more acid, but the concentration of phytin is significantly reduced as the sparging progresses. Therefore, its appropriate to not include that pH reduction in the sparge water calculations. Only use the acid's contributions.

PS: Yes, this response did make my brain hurt!

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Old 02-02-2013, 06:49 PM   #12
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Martin,

Thank you so much for your response! Your posts in this thread and throughout the forums has taught me so much! Your willingness to help does not go unappreciated!

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Old 02-03-2013, 01:30 PM   #13
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Originally Posted by mabrungard View Post
A more appropriate way to evaluate the concentration of bicarbonate neutralized is to look at the difference in the starting and ending alkalinity. Say you are at 152 ppm alkalinity as CaCO3 and you want to end up at 25 ppm. That is a reduction of 127 ppm alkalinity. 1 ppm alkalinity (as CaCO3) is equal to 1.22 ppm of bicarbonate neutralized. So the bicarbonate neutralized by the sparge acidification is 127ppm x 1.22 = 155 ppm bicarb (-155 ppm bicarb). Since lactic acid is monoprotic, that means that 155 ppm of lactate is added to the sparging water when neutralizing that much alkalinity.
This calculation is not quite correct. To neutralize 1 ppm alkalinity you need 0.02 mEq/l acid. And since lactic acid is monoprotic as you said you need 0.002 mmol/l lactic acid. with a molar weight of 90 g/mol you need 1.8 mg/l lactic acid (that's also the amount of lactate you'll get) to neutralize 1 ppm as CaCO3 alkalinity. For 100 ppm alkalinity this would be 180 mg/l lactic acid.

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Old 02-03-2013, 05:24 PM   #14
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Kai,

Thank you for your response! I updated my spreadsheet.

This leads me to another question....

Using your 1.8 mg/l, I figured out that the total lactate ppm from my mash and my sparge (total water) is 198. Is the lactate boiled off during the boil? If not, would the entirety (or most of it) still exist in my boiled wort? The taste threshhold is 200-400ppm... If my lactate content is 198ppm in 10.17gallons of initial water, I figured I would be fine. However, after mash and boil-off I'm left with about 6 gallons. Anyways, is the taste threshhold based on the initial water or what's left after boil-off? There are so many factors that seem to come into play here, it's sort of overwhelming.

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Old 02-03-2013, 06:01 PM   #15
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I think it is more practical to express the lactate as lactate per grain weight. With that approach you don't have to worry about boiling (which does not boil off lactate) concentrating your lactate. Furthermore it takes into account that more grain per water usually means higher gravity and with a higher gravity the lactate taste threshold should increase.

There is a general rule of thumb that one should not use more than 5 % acidulated malt. That's why I think its useful to express lactate as equivalent percent of acidulated malt used.

When it comes to the taste threshold of lactate, I haven't seen much data except for a few rules of thumb here and there. But those rules seem to make sense, though.

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Old 02-03-2013, 09:50 PM   #16
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Sorry, but no. Lactate per grain weight would not be a good measure. I'm afraid I am not following Kai's logic above. The argument based on a percentage of acid malt is dubious at best.

A little more research might have been wise before commenting on lactic acid taste threshold. I pulled out my copy of Malting and Brewing Science and found a published reference. Fortunately for Kai, he can just Google 'lactic acid taste threshold' and he will be whisked to page 849 in that book via the courtesy of Google.

Additionally, the fermentation by-products of yeast include lactic acid. Some yeast are more prolific than others at producing acidity, so I assume that some have varying degrees of lactic acid production. That is why its important to limit lactic acid additions to create something less than 200 ppm to avoid most people's taste thresholds. That still could leave a person that is sensitive to that taste, disappointed. In the OP's case, I'd seriously consider moving to phosphoric to avoid the effect all together.

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Old 02-03-2013, 10:16 PM   #17
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Thank you both for the help once again.

I will consider using phosphoric acid for my next batch. In fact, i'll probably just dillute it a little more and add more salts. However, I used lactic acid in the batch I just brewed yesterday.

I'm trying to keep this as simple as possible, while keeping the taste threshhold in mind. I found somewhere (probably in these forums), that 400ppm of lactate per gallon is approximately 1.25mL of lactic acid. As Kai said, lactic acid is not boiled out, so the amount of acid I used in my total starting water would be carried over to my fermenter. Thus, if 400ppm of lactate in a 5.5 gallon batch (to my primary) is approximately (1.25mL * 5.5=) 6.875mL, and I used 4.09mL of lactic acid in my total water, I would end up with roughly (4.09mL / 6.875mL * 400ppm) = 238.06ppm. I don't know how accurate this is, but if it gets me in the rough ball park it will work for me. So, I'm a little over your recommended limit Martin, but hopefully it comes out ok.

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Old 02-04-2013, 04:00 AM   #18
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Quote:
Originally Posted by mabrungard View Post
A little more research might have been wise before commenting on lactic acid taste threshold. I pulled out my copy of Malting and Brewing Science and found a published reference. Fortunately for Kai, he can just Google 'lactic acid taste threshold' and he will be whisked to page 849 in that book via the courtesy of Google.
Thanks for that pointer. I took a look and it only mentions a taste threshold of 400 ppm for lactic acid. No mention of the source or if there is a dependency on beer strength. Given that this book is targeted towards large commercial brewers i assume that this number is for regular strength (12 P) beers. Your limit of 200 ppm for lactate added during brewing makes sense and comes out to about 4% acid malt for a 12 Plato beer brewed with good efficiency.

But nothing here is an argument against reporting the added lactate on a per grist basis.

I think either way will work for brewers as it keeps them away from adding too much lactic acid.

On a side note, I also checked Narziss' Technologie Der Wuerzebereitung and while he does not mention a taste threshold he mentions Sauermalz additions as high as 8%, which I find a bit high.

Kai
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