Iodine testing
When using iodine to test mash conversion, does it matter where you take the sample from? i.e. whether from the top of the mash or from the recirculated runoff. Will sucking up a few crushed bits of grain in the pipette for the sample throw out the iodine test and will testing just the recirculated runoff be artificially removing starches due to the filtering effect of the grain bed therefore giving a false positive iodine result?
Replies to This Discussion
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Permalink Reply by denimglen on
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...Will sucking up a few crushed bits of grain in the pipette for the sample throw out the iodine test...
It could do if your crush isn't fine enough and there's still unconverted starch in the middle.
...will testing just the recirculated runoff be artificially removing starches due to the filtering effect of the grain bed...
I wouldn't think so - the starch particles should be small enough to make there way through the grain bed.
Is there any specific reason you're testing for conversion?
To be perfectly honest I find it's a complete waste of time. A good crush, correct pH range, and correct temperature range should produce a mash that will convert in around 15 - 20 minutes. I'm only mashing for thirty minutes now on sub 70-point beers.
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Permalink Reply by DP on
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Thanks Denim.
My previous batch never really lost the purpling of the iodine (even after 90 mins) and I was sampling from the top but was sucking up lots of bitty bits. Last night's batch I measured from the recirculated runoff and it tested clear first off. So I wasn't sure whether I was doing it wrong the first time. I might do an iodine test on both the surface of the mash and the runoff at the same time in the next brew just to see if there is a difference in colour.
Is there any specific reason you're testing for conversion?
Yup; I'm new to AG and am unsure that I have a good crush, correct pH and the correct mash temperature and so I'm measuring the hell out of anything and everything at the moment. My last few beers have been a bit lacking in body (among other things) and so I've increased the mash temp a bit and figured I might as well see if everything was converting as it should.
Besides, I kinda like measuring stuff. :)
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Besides, I kinda like measuring stuff. :)
Fair enough.
I could never really get the iodine test to work myself, so gave up on it.
pH is usually 'close enough' (but if you like measuring stuff grab yourself some heroin scales and start playing with water salts :-) )
Your temperature should be sweet if your thermometer is reasonably accurate.
A good way to see if your malt is crushed enough is at the end of the mash grab a few 'hunks and squish them between your fingers, if there's still dry starch in the middle you should aim to crush tighter.
My beers were also lacking body and finishing too low, part of the reason why I dropped my mash time. I was getting too big of a temperature drop in the last bit which was breaking down too many sugars. By increasing your mash temp you're compensating for that so it should work out well for you.
Hope that helps mate.
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Brewers Coop are crushing my grain at the moment as I don't have a mill of my own (and I don't think my Financial Controller will allow me to have one for quite some time yet). Is their crush about right?
I'm on the North Shore and have read that our water here can benefit from a teaspoon or so of gypsum and so have been adding that lately but haven't really noticed a huge difference.
I'm mashing in a chilly bin and have a handheld thermometer but was getting quite inconsistent readings so I was never really sure what the temperature was doing. But last week I installed a MashMaster analog probe in the side of the mash tun and noticed last night that I dropped from ~68C down to 65C in 30 minutes so topped it up with some hot water to bring it back up to 70C. Hopefully this will help with the body issue I'm having. It's also nice to be able to see the temp without having to crack open the lid.
I've tried using litmus papers to measure the pH but I'm not very good at reading them. In fact I gave up after one try. Perhaps I should give it another go.
Cheers for all the help; I really appreciate it!
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Permalink Reply by vdog on
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Your crush should be sweet if Mike's doing it for you - that should be one less thing to worry about anyway!
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Mike at BC was crushing for me before I got my own mill. His crush is OK. Personally I like it finer but I know he has to crush the malt to suit even the worst lautering systems so I do understand it not being as fine as most would like.
For shits and giggles you could get him to run it through twice for you if you wanna see how that effects things.
Smack the person that said a teaspoon of gypsum will improve your beer :-P haha. It's kinda like saying an extra palm-full of hops will make the beer better - but that depends on the beer the same way salts do.
Water chemistry can be pretty daunting at first - I would recommend leaving it to the side until you get used to all the other aspects of AG. But once you understand it, it's pretty simple and can improve your beers greatly.
Temperatures in the mash tun are usually pretty inconsistent I reckon - just the nature of the beast. As long as your average temperature is what you're aiming for - you're good. I also have the MM thermo on the side of my tun and that is my one and only reference point. It's just part of learning your own brewery. While 68C mash in my system will be different to 68C on your rig, I can get an idea of what my FG should be and my attenuation with 'x' yeast will be and work my mash temp from there. After a few batches you'll get the gist of it.
Litmus/pH papers are pretty shit I reckon. Most of them have too broad of a pH range for mashing and you also need to have a a good eye for colour to get any sort of accuracy. You also have to hope whoever printed the reference paper did a hell of a good job of matching the colours. Digital pH meters are the only way to go I reckon, and well worth the 70 or so bucks you pay for them. BUUUUUUUUUUUUUUUT! In saying that, I used to check my mash pH everytime. But I haven't taken the pH meter out of its case for the last 10 batches or so - because John Palmer's residual alkalinity spreadsheet (used to calculate the pH of the mash with salt addtions) is so bloody spot on it's not worth my time to even look through my tool box to find the meter.
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Sorry, I should have clarified exactly why I was using the gypsum. I was finding that my ordinary bitters were lacking in hop character (as well as body as mentioned above) even when using tried-and-true recipes. I went looking for solutions and found a calculator based on John Palmer's spreadsheet and nomograph which, when I plugged in the figures for my local water, showed that for it to even be within Palmer's recommended mineral ranges (just for beer in general let alone a particular style like a bitter) I need to add 1tsp gypsum per 20L or so.
My local water's residual alkalinity and chloride to sulphate ratio makes it more suitable to a light but malty beer so I figured a dash of gypsum wouldn't hurt and I have to say that while there hasn't been an amazing improvement it's definitely not harmed it in any way.
But, you're right, I could easily imagine getting lost in minute salt adjustments when I ought to be focussing more on the basics (like ensuring that the mash is actually converting properly in the first place!).
I guess that -- as you say -- it's a matter of learning the individual quirks of my system. i.e. it might turn out that to achieve a medium body mash on my system the temperature gauge should read 68-70 whereas on others it might be 65-68.
Still it's a shitload of fun brewing and then drinking the results! :)
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Haha, my bad on the gypsum mate, you're on the right track then.
If you aim to get 50 - 100ppm Ca in your water then your mash will convert better, so it's worth keeping the gypsum in there.
It sounds as if your water is on the tame side, low in minerals all round, so even a general water profile for all your beers should help improve them quite a bit. Something like 50 - 100 ppm Ca, around 50 - 75 ppm of both SO4 and Cl, and however much HCO3 you need to balance it all out.
Brew strong bro!
PS - unless your getting sub 60% efficiency into your fermenter or starch haze problems I wouldn't worry too much about full conversion. I found and posted up a pretty in depth efficiency calculator in the library thread that you may want to have a look at and play with on your next batch that's probably a little more reliable than the iodine test (and also gives you a reason for taking a few more measurements ;-)
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Cheers for all the help mate. It certainly makes learning the dark arts a lot easier when people are happy to give advice!
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Permalink Reply by Doublehoppy on
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A tip I picked up from Denim for helping to maintain the temperature in a chilly bin is to fit a piece of styrofoam inside to reduce the amount of dead space.
Buy a cheap kids surfboard from the warehouse, cut to size and fit a string "handle" and you're away -
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This week I went to Placemakers and picked up a block of 60mm thick underfloor insulation polystyrene (for ~$7) which I've cut down and tapered to wedge into my chilly bin. Nice snug fit with a little notch at one end to get a finger in to pull it out again. It'll be interesting to see what difference it makes to the stability of the temperature throughout the mash. Cheers for the idea!
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Permalink Reply by Jona Hjelmstrom on
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I observe a frothing activity on the surface of a mash, which I presume is the diastase enzyme doing its magic on the starch.
After a couple of hours that activity has ceased, so it must be a done deal with the starch conversion.
The 'eyeometer" method ?
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