Lactic Acid or AMS/CRS?

[MmmBeer]

Last night I drew off a sample of a best bitter, which I kegged about a week ago and when I tasted it, I noticed an odd off flavour. After a few more sniffs and tastes it began to remind me of the aroma of milk, I have noticed this in a beer a few years ago, when I had used Lactic acid to remove alkalinity and had probably used too much. Checking the recipe, I used 10ml AMS in the mash and 10ml in the sparge, however when brewing this beer, I opened a new batch of AMS. This AMS was part of an order from a major supplier, added in to counter the shipping costs, and it had arrived in plastic screwtop tubes with hadwritten labels rather than a proper printed bottle.

So now I am wondering, is it really AMS in those tubes, or could it be Lactic acid? Is there a simple way to differentiate between the two without needing full lab facilities? Alternatively it could have been an infection with a bacteria that produced Lactic acid.

I am planning to brew again in the next few days, so I will probably work on the basis that it is Lactic and therefore use in much smaller quantities, well below the taste threshold and will probably amend the recipe to make it a somewhat darker colour and reduce alkalinity naturally.

 

[Brianbrewed]

Depends on your water profile.
Where I live the water is harder than concrete.

I use RO water and salts to hit my ph.

 

[strange-steve]

Take a few litres of water, test the alkalinity, add a known quantity of your mystery acid, retest the alkalinity.

An addition of 0.1ml/L of AMS will remove around 20ppm alkalinity, the same amount of lactic acid will remove about 50ppm.

Even if this test isn't entirely conclusive, it'll let you know how much acid to use in future brews.

 

[MmmBeer]

The KH reagent in my Salifert test kit has run dry, I think the bottle leaked at some stage and there is now not enough left to complete the test. Will order another kit and test then.

 

[crescent city Mike]

Lactic acid and Phosphoric acid are used to get the pH down to the magic number for your mash. Some recommend using the phosphoric acid as it is more neutral in flavor. I used Lactic 88% and calculate the amount with Palmer's RA worksheet calculator. You can google it and download for use. It also has a very useful calculator to determine how much to add to your sparge water.

 

[johncrobinson]

I agree with crescent city Mike, Phosphoric acid actually tastes quite nice despite the name.

 

[Northern_Brewer]

Lactic acid and Phosphoric acid are used to get the pH down...

In the US.

But being British the OP thought he had bought AMS, which is a blend of hydrochloric and sulphuric acids that is the normal acid used in British brewing. And in which are the obvious ones to use, let's be honest - it's only legal restrictions that have pushed US brewers into using daft acids like lactic.

Steve's is probably the sensible way to do it, I guess you could test for the presence of sulphate by adding some calcium chloride and neutralising the acid - calcium sulphate is not very soluble at pH7, whereas calcium lactate should be soluble if I remember my chemistry right.

Or you get into trying to oxidise the hydrochloric to chlorine gas and sniffing it!!!!

 

[MmmBeer]

Still waiting for the test kit to arrive, but have brewed using the acid, as if it was lactic, a total of 5ml in 23l of a nice dark Old Peculiar clone. The mash pH was flitting between 5.3 and 5.4, which is good enough for me.

I think I would struggle to make a pale beer with my tap water and this, if it does turn out to be lactic.

 

[crescent city Mike]

I would suggest that you download "John Palmer's RA Worksheet." It can deal with almost any scenario you can imagine. You can fill in the info on your source water and then your target water. You can then add a variety of minerals to adjust your water to what it needs to be. There are places in the worksheet to calculate how much and what kind of acids you want to use. The intro page describes what residual alkalinity is and how to deal with it. I've found virtually NO need to guess anymore.

 

[MmmBeer]

I have all the information I need to build up my required water treatment. My problem is that I suspect that the AMS I bought, may in fact be Lactic acid instead.

 

[The Baron]

If it is indeed Lactic acid 20ml is a lot to put in so that may answer your question but listen to Steve he is one of the senior water experts on this forum

 

[johncrobinson]

He is indeed my dear Baron,

 

[strange-steve]

he is one of the senior water experts on this forum

This must be a terrible forum then :tinhat:

 

[MmmBeer]

Take a few litres of water, test the alkalinity, add a known quantity of your mystery acid, retest the alkalinity.

An addition of 0.1ml/L of AMS will remove around 20ppm alkalinity, the same amount of lactic acid will remove about 50ppm.

Even if this test isn't entirely conclusive, it'll let you know how much acid to use in future brews.

I finally received my new KH kit and tested my tap water and compared with a sample treated with this acid (1 ml in 4 l of water).

	ml KH reagent	dKH	Alkalinity (ppm CaCO3)
Tap water	0.52	7.3	131
Treated with 0.25 ml/l acid	0.74	3.8	69

This represents a reduction in alkalinity of 62 ppm.

Therefore an addition of 0.1ml/litre would result in a reduction of 25 ppm, half of what would be expected for Lactic. This is also slightly higher than the 19-20 ppm reduction expected for AMS, but close enough and within margins of measurement error.

I will tread carefully for my next couple of brews, underdosing slightly and shying away from anything too pale until I am 100% confident with this acid.