Advice on spectacularly bad mash conversion

[chrisr]

I’ve just brewed a saison (actually, Malt Miller’s Dupont). The outcome was a staggeringly low mash conversion: 47%. The result was 6 litres less saison than expected.

Any suggestions as to what could produce such a pathetic conversion?

It was all grain, all the grist mashed together, at 63C, in a RIMS system, so it maintained that temperature. It was 1½ degrees under temperature at dough-in, but it soon made that up. The mash pH was 5.37 at 15 minutes in. I did stir well at the start, and again at 45 minutes-ish. The total mash time was 75 minutes. It was batch sparged, the first run-off was 9 litres, the second I stopped at a further 7 litres, as the gravity (of the whole) was becoming too low to produce the required strength beer. The liquor was 55ppm Ca, 53ppm Cl, 105ppm SO; the RA calculated at -130, for a 8.5 EBC beer. There was 25ppm SMB added to the mash, for anti-ox & chlorine removal purposes. It took 1.4ml of lactic acid to get the mash pH to 5.37 (this was pre-calculated as 1.2, but tweaked on the fly with a further 0.2).

I regularly get ‘short measures’ from my brews, but usually only a litre or two; this one was spectacularly bad. Conversely, I sometimes (much more rarely) get better extraction than I calculated. I do strive for consistency, and every brew uses the same methods and equipment.

[Jim]

Have you used the same batch of malt before so that you know it's good?

[MashBag]

I regularly get ‘short measures’ from my brews, but usually only a litre or two; this one was spectacularly bad.

This is the bigger question for me.

What water do you have? Is it drinkable?
Have you seen the water report ?

I think we need some of the numbers people....

[chrisr]

@Jim, it was a Malt Miller kit, all the grist, ready to mash, in a bag, so no. That is a possibility, but I've never had dodgy ingredients from MM before. I'm open to all suggestions though.

@Mashbag, I'm in the north midlands, the water is 'municipal' water, quite drinkable, soft, the source is surface water. I believe the composition does vary slightly, over the seasons. Before adding anything:
pH around 7 (this does seem to vary, it may go up to 8 sometimes)
Alkalinity 12-16mg/l CaCO3
Carbonates, I've no idea
Ca 14-15mg/l
Mg 3-4mg/l
Cl 13-14mg/l
SO4 25-30mg/l
Na 9mg/l
(It's the same water used by Thornbridge Brewery)

As I said, after brewing salts were added it was 55ppm Ca, 53ppm Cl, 105ppm SO4.

[Trefoyl]

I’ve never had any success with batch sparging and would get results similar to yours when the runoff is too fast. Fly sparging with a slow runoff gives me the best efficiency and predictable results.
Obviously other people do very well with batch sparging or even no sparge, so not sure what the trick is.

[Jim]

..........I've never had dodgy ingredients from MM before........

No, me neither.

I was never a batch sparger so I don't know what the pitfalls are, but I have a sneaking suspicion that's where the trouble lies.

[Eric]

47% is staggeringly low. Regardless of water profile or mash pH, you should get more than that.

I too fly sparge and usually get over 90% extraction. That level can't be achieved in a hurry, sparge too quickly and much will be left in the grains. With a floating grainbed, a gentle flow of sparge liquor can rinse out nearly all sugars, but that's not the case here.

Ordinarily I can extract half the grain's sugars by a quarter to a third of the required boiler volume. Initial runnings should be at about 1080 in a moderately thick mash and that should run for little while, so for a 1040 beer it should not take long to extract a significant proportion of that required.

You use RIMS. I did for a while and was ever concerned should the element exceed than the upper temperature limit of the enzymes. It didn't happen to me, but in doing so found it near impossible to raise the mash temperature without running that risk. However, the alpha amylase can survive higher temperature than the beta resulting in higher extraction than you got, but with the product not very fermentable. Your water is soft, and with limited calcium content offers little protection to alpha and beta amylase. Do you know what temperature the wort reached when recycling?

[MashBag]

Eric I agree with your points.
I think we are looking at a equipment or a process problem here. This is not a one off incident.

Ultimately the question is..
Is it converting and not sparging
-or-
not converting in the first place.

IMO the latter is most likely the case.
So the thermometer/controller faulty?
Or as you suggest the element too dense / pump too slow and the recirc is killing the enzymes?

I think a water only run would tell you a lot, you watch carefully and test temps.

@Chrisr Can you give us a bit more detail on your system? Bought or built, vessels and pump. Heater wattage in particular please ?

I have a heavily modified BM (technically RIMS) and don't gain much by sparging.

[guypettigrew]

I’ve just brewed a saison (actually, Malt Miller’s Dupont). The outcome was a staggeringly low mash conversion: 47%. The result was 6 litres less saison than expected.

It was all grain, all the grist mashed together, at 63C, in a RIMS system, so it maintained that temperature. It was 1½ degrees under temperature at dough-in, but it soon made that up. The mash pH was 5.37 at 15 minutes in. I did stir well at the start, and again at 45 minutes-ish. The total mash time was 75 minutes. It was batch sparged, the first run-off was 9 litres, the second I stopped at a further 7 litres, as the gravity (of the whole) was becoming too low to produce the required strength beer. The liquor was 55ppm Ca, 53ppm Cl, 105ppm SO; the RA calculated at -130, for a 8.5 EBC beer. There was 25ppm SMB added to the mash, for anti-ox & chlorine removal purposes. It took 1.4ml of lactic acid to get the mash pH to 5.37 (this was pre-calculated as 1.2, but tweaked on the fly with a further 0.2).

I regularly get ‘short measures’ from my brews, but usually only a litre or two; this one was spectacularly bad. Conversely, I sometimes (much more rarely) get better extraction than I calculated. I do strive for consistency, and every brew uses the same methods and equipment.

For this brew you used the same gear and (roughly) the same technique you've always used.

But it's an interesting technique. You added Sodium Metabisulphite to the mash. A new one on me! In weight terms, how much did you add to how much mash liquor to add 25ppm?

I don't know what RA stands for, or what -130 means.

You used lactic acid to drop the mash pH to 5.37. I'll assume you'd calibrated your pH meter. So you measured the pH, added some lactic acid, measured it again and added some more.

You stirred the mash after 45 minutes. Again, a new one for me. Once my mash has started I actively ignore it for about 90 minutes.

You only collected 16L before the boil. Presumably 13L after the boil?

The points Eric has raised are all valid. Your Calcium is low and a very quick Google search suggests lactic acid might further reduce it. Unsure of this, though. Advice from a chemist would be useful.

Eric's point querying whether the RIMS set up might have denatured the enzymes is worth pursuing.

I also wonder if stirring the mash 30 minutes before batch sparging might be unhelpful.

As to batch sparging, I've never tried it. It doesn't seem right, somehow! I fly sparge and, apart from the very odd occasion when I rush it, also get >90% mash efficiency.

Mind you, none of this really explains how you got such low efficiency when using the same process on the same kit as you always have done.

Have you got any thoughts, chrisr, from all the comments which have been made so far?

Guy

[chrisr]

Thank you all for the responses. Several things to think about there.


RA = residual alkalinity

I did used to fly sparge, but kept getting low efficiency, even though I took about 2 hours to do the sparge. I switched to batch sparging, and got much better results.

The RIMS system I made myself, with the aim of holding temperature rather than being able to raise it (by any significant degree) so the heating element is a small thing. It’s a long time since I built it, but I think it’s 400 watts (might even be 200w). The heated flow back into the tun is maybe 5 degrees warmer. But, anyway, lots of people have much more powerful RIMS systems and seem to have success using them.

The temperature control is accurate, I have cross-checked with a separate thermocouple sensor, from time to time.

The SMB added to the mash was 0.45g. It’s to reduce chlorine/chloramine taints and to provide some anti-oxygen effect.

Yes, the pH meter was calibrated before use. Yes, added the calculated amount, then checked and adjusted with a bit more.

The calcium: yes, I agree, rather on the low side, but (after some Googling) I decided that was probably suitable for a saison. Normally, I would aim for around 100ppm Ca, or even more in 'bigger' beers.

I gave up doing the iodine test years ago, as every time I tested, after an hour, the indication was the conversion had completed. So now I just leave it 75 minutes and assume all is well.


So far, based on what people have said, my feeling is the sparging is the problem. But as I say, I used to get – generally – worse outcomes fly sparging, even though I was taking 2 hours over it. Moving to batch sparging improved things. I will try fly sparging again, on my next brew. How long should I take over the fly sparge (25l mash tun, 5-6kg grain)?

[Jocky]

My process for batch sparging is:
Add the batch sparge water
Stir well
Leave it 5 minutes
Stir again
Recirculate a few litres to remove any fine malt dust
Run off as fast as you can.

Two sparges are always more efficient than one, but to be honest by the time I’ve done that sparge process twice it’s not much faster than doing a 1 hour fly sparge.

[Eric]

My RIMS had a 750 watt element controlled by 3 temperature probes, but didn't work as I'd hoped.

Play with RA all you like, it won't help.

While measuring pH is vital to ascertain if your brewing is going as it should, mash pH has more influence on what what you get from the grains than how much. Maximum extraction at optimum pH is not much more than from an out of range pH. Too high pH will extract what you don't want and too low will result in wort that won't fully ferment.

I don't need SMB and it is a long time since doing an iodine test.

Brewed today, calcium set at 170 ppm.

Sparge started immediately after recycling a litre or so for clear wort, runoff and sparge rates were equal, keeping the grains in place so the liquor made its way gently through the grains.
This was in a single pot, with grains in a malt tube meaning 50% more liquor for the mash than would be used in my 3V system. This caused the first runnings were 1075, the wort run into a second vessel then returned for the boil. 30 litres containing 92% of the maximum potential extract was collected, 47% by 9 litres, 55% at 11, and 68% at 15 litres, that was half the final volume.

You didn't give any figures to support your findings, did you measure the output with a hydrometer and if you did, did you compensate for temperature?

[chrisr]

@Eric

No, I don't target RA, I target the pH. The RA is whatever it is to get the pH in the right range. I intended the pH to be about 5.35 for this mash.

I agree with you on the calcium. Normally I would have gone higher, but the gist of Googling 'saison water chemistry' was to go lower on all the brewing salts/ions.

Yes, I was using a hydrometer and did adjust for temperature. I didn't take any measurements as detailed as you quote, I was just measuring the density of the whole of the run-off.


@jockey, yep, that pretty much what I did, only I recirculate for 10-15 minutes before starting the second run-off


Anyway, after reading all the responses from everyone, my feeling is sparging was behind this. I'll give fly sparging another try on my next brew and hope it goes better. Thank you all for the ideas.

[Eric]

There is a further reason that might explain such a low figure. I don't think it is likely the efficiency would be as low as you report, and that is layering.

It would appear that I achieved greater extract from my mash from the first 9 litres of 30, that is less than a third of the full volume, than you got from your full volume. I doubt that is likely and suggest that the runnings from your second sparge which you reported were low enought to cause you to stop, didn't fully mix with the rest of the wort and the layer in which your hydrometer floated was quite heavily diluted by the last sparge. Potentially the sparge liquor was hotter than the bulk of the collected wort and being lower gravity congregated at the top.

If this might have been the case, in future give all the wort a good stir before taking a reading.