Sparging methos and run-off pH

[P]

Hi all,
I have a question related to grist buffering capacity vs. sparging methods.

I have read that fly-sparging poses a risk if the water used is alkaline as the pH may rise making tannings and other non-desirable compounds more soluble.

I have also heard Denny Conn stating that this is not an issue if you batch sparge ... Perhaps I misunderstood his comment but I don't understand why is there a difference:

If the same amount of water is used for either fly or batch sparge, the amount of alkalinity in it and therefore its capacity neutralize grist acidity is the same .. so why would batch sparge be "safer"?

Is the buffering capacity of the grist non-linear as to be affected differently if you trickle water through it as opposed to just dumping it all at once?

Thanks,
P

 

[UgliestLemming]

One of the reasons may be channeling while fly sparging... I acidify my sparge water with some 88% lactic acid, then no worries.

 

[GernBlanston]

The theory is that with a fly sparge, the pH is effected as the wort is diluted. At the end of the sparge, and if the sparge runs too fast, when the wort gravity drops, and the pH will change, causing tannin extraction. This only happens when the gravity gets low. If channeling is occurring, the water running through the mash has an inefficient extraction, resulting in low gravity, hence possible tannin extraction.
A batch sparge uses a water volume that allows extraction without dilution, and then it is run off, usually quickly as channeling is not an issue, therefore the solution never reaches the critical dilution gravity that causes pH changes.
That is the theory.
I have always batch sparged, thanks to Denny's guidance many years ago, so have never experienced this phenomena.

 

[Ozarks Mountain Brewery]

the only issues with sparging come into play when you heating up to 170 and running water slowly through the grain for a long period of time to extract more sugar within the grain not just the outside, "Call it what ever name you want" most people do not do this today unless they have a very good set up. and it does run the risk of pulling other nasties out of the grain ... in most cases its not even necessary

In the beginning when you mash the grain brings your ph down a lot lower than you think but when you sparge it doesn't so you have to lower your sparge water to at least 6 ph or it can have the same kinds of effects

dumping water on top and draining it as you dump should not cause any problems but you still need to lower the ph in the water

if your like me and you do a circulation for 60 minutes, long slow sparging is not even necessary, the only thing thats left is washing the sugar off the out side of the grain and you don't even need 170 water for that process just drain your mash and recirculate with the clean sparge water for 10 minutes, not undesirables will emerge

 

[P]

One of the reasons may be channeling while fly sparging... I acidify my sparge water with some 88% lactic acid, then no worries.

To what level you acidify? Do you target a particular alkalinity number on your sparge water?

I still don't understand the real reason behind the difference between the two methods.
My thinking is fixated only around the buffering capacity of the malt and the alkalinity of the water used for sparging. Once the buffer capacity is exhausted, the pH will raise rapidly, regardless of the method (many articles I read contradict my statement, I just want to understand why my thinking is wrong).

I read threads and articles that talk about fly-sparging until reaching certain gravity. It is said that that above this gravity we are good, below this gravity we extract tanins ... I don't buy into that. Try fly-sparging with the tap water I get which has an alkalinity of 300-350 CaCO3 and I bet you'll be at pH 6 way before reaching the gravity limit.

thanks for all the answers chaps... you are probably thinking, why don't you just drop it and get on brewing!

 

[The Brew Mentor]

P,
The differences in overall PH in your grain bed when comparing batch and fly sparging can be significantly different. Even if the same amount of wort is collected.
For example, lets look at a simple batch and fly sparge.
Batch sparge...
Mash 15# grist with 5.5 gallons of water. Target mash ph is 5.2. After mash is completed, collect +/- 4 gallons wort. Then add 2.5 gallons of 7.2 PH sparge water to mash tun and mix completely. the resulting mash PH may be +/- 5.6 and that is run off and added to your BK for a total of 6.5 gallons of pre-boil volume.
Fly Sparge...
Mash 15# grist with 5.5 gallons of water. Target mash ph is 5.2. After mash is completed, start fly sparging slowly by continuously adding 7.2 PH water to the top of the grain bed while collecting wort. With a proper manifold or false bottom in your mash tun and no channeling, the heavy, sugar laden wort will stratify and come out the bottom and the lighter water will remain toward the top, pushing the wort. 6.5 gallons in the top, 6.5gallons out the bottom. The difference is that over the fly sparge, the top of the grain bed has had a significantly reduced PH and the bottom of the grain bed has been higher. This lower PH in the top of the grain bed may extract tannins and if any channeling occurs, end up in your mash tun.
This is why when fly sparging it is important to go slowly and have a good manifold or false bottom setup to prevent channeling.
On smaller systems, it's faster and easier to batch sparge. On bigger brew houses fly sparging is a better option.
Make sense?
Brian

 

[P]

Yes, makes sense!

In fly sparge, part of the bed is more exposed to the alkaline sparge water, the buffering capacity of this section of the bed will be exhausted and we may end up extracting tannin from it.

In batch sparge, all the grain is equally exposed to the alkaline sparge water and the overall buffering capacity is grater in comparison to fly sparge where only a fraction of the bed fights the water alkalinity.

Thanks for that.

 

[Nosybear]

Acidify all your water to pH 5.5 after adding enough calcium that you have at least 50 ppm Ca++. Cap the mash with your dark grains/crystals at vorlauf. Those methods should keep our pH in an acceptable range and give your mash enough calcium to work effectively. Much simpler than agonizing over each ion. And always, RDWHAHB.

 

[Nosybear]

Forgot to mention: Acidify with phosphoric acid - least flavor of all strong acids. I use a 10% solution.