5.2 pH Stabilizer
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5.2 pH Stabilizer (shown in picture) is a product sold by Five Star Chemicals that according to their website "is a proprietary blend of buffers that will lock in your mash and kettle water at a pH of 5.2 regardless of the starting pH of your water". The manufacturer states that one tablespoon per 5 gallons of finished beer is all that is required.
At first glance it would seem like an easy way to always lock your mash in at a pH of 5.2 for perfect starch to sugar conversion. (They don't mention if they mean relative to room temperature or mash temperature).
We tried this product with a simple Blonde Ale using our very soft city water which has a high pH of over 8 (relative to room temperature) when untreated right out of the tap. This beer was made mostly with lighter coloured 2-row grain. There were no darker grains that would help lower the pH into the proper 5.2 pH range (relative to mash temperature) so we knew that some extra help would be required even after we added our usual brewing salts to alter the flavour profile the way we wanted. Many of the brewing salts we use lower pH, but often not enough.
Even though our water's pH is very high it's very soft (has a low buffering capacity or residual alkalinity) so it doesn't take much to lower the pH. Normally if our mash pH is still higher than 5.2 (relative to mash temperature) after we add our brewing salts and re-measure, we add a bit of 88% lactic acid to bring the pH down further. It usually only takes one millilitre (mL) or two at most with our 10 gallon batch size. This seemed like a good test to try the 5.2 pH Stabilizer instead.
We mixed in our grain with the strike water (called 'doughing in'), along with some salts, and let it sit for a few minutes. Our mash pH measured 5.59 (relative to mash temperature). The grains and salts had dropped the pH of the water from over 8 all the way down to 5.59. Not bad, but still too high, as it should be around 5.2 to 5.3.
So we added 2 tablespoons of 5.2 pH Stabilizer (the instructions say to use 1 tablespoon per 5 gallons of final product and we're making 10 gallons), stirred well for a few minutes and then measured again to find that it was now 5.55, or a drop of only 0.04. Hmmm, not very much of a drop at all. What happened to that claim of "locking in our mash pH at 5.2 regardless of the starting pH of our water"?
So we added two more tablespoons and saw another small incremental drop in pH to 5.51. This is clearly not working as well as we had hoped. We stopped there as we did not want to add a total of ~20 tablespoons of this product to our beer to attempt to lower the pH to 5.2 as required.
It's important to note as well that this product only addresses mash pH. We don't know exactly what "food-grade phosphates" are used (they don't tell) so we don't really know what it will do to the flavour profile of the beer.
We've heard other brewers that swear by 5.2 pH Stabilizer. It may be that the product works as advertised, but only for water with a mineral profile and pH that falls within a specific range. What mineral profile and pH range? We don't know. The manufacturer doesn't specify. It may also be a placebo effect on the part of the brewer who expects the product to work as advertised.
We recommend that brewers instead learn how to adjust their water using salts with known flavour outcomes and measure the pH themselves. This ensures that *you* the brewer remain in control of the mash pH and flavour profile and that you know exactly what you're drinking. Not sure how to do this? See our Water Adjustment guide.
If you don't want to manipulate your own water, then by all means use 5.2 pH Stabilizer, but we would suggest that it be used sparingly (no more than a tablespoon or two per 5 gallons, and only in the mash). Measuring pH would also be useful so that you have some idea of how much it's actually helping.
Addendum: After much research we believe to have found some old information from Five Star Chemicals that describes what is in the product. To quote the company:
"... The 5.2 stabilizer is a blend of two salts. They are neutralized versions of phosphoric acid. They are monosodium phosphate (Na H2 PO4) and disodium phosphate (Na2HPO4) in the right ratio they will form a buffer that locks the pH at 5.2..."
We have no idea how either of these salts affect the flavour of beer so we still suggest that most people stay away and instead treat their water and mash using salts with known outcomes per our Water Adjustment instructions. The common salts we use have been brewed with for many years (they exist naturally in water) and the outcomes are widely known.
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