# Iodophor For Starch Conversion Test



## BjornJ (2/1/12)

hi guys,
I wanted to do a starch conversion test today for the first time.
Sharing it here in case there are others who haven't tried it either.


I use Iodophor no-rinse sanitiser so doing the starch conversion test with that after reading about it;
http://www.homebrewtalk.com/f39/iodophor-s...sion-test-5132/ 

My understanding is that if there are starches left in the mash, the iodine in the iodophor will make the iodophor/wort mix go purple.

This would show the mash is not complete, there are unconverted starches not yet turned into fermentable sugars.

A couple of minutes after doughing in at 55 degrees C I took a small amount of wort into an egg cup.
Left it on the bench top for 5 min or so to cool down to room temperature.

Sprayed a bit of iodophor on a white saucer, then dripped some wort in the middle of it.


The iodophor was orangy in colour, a couple of seconds later there was clearly purple colour in the middle.





I take it that means this works, and that I can use it to test after the mash as well.

I also did a mash pH test, something I always struggle with reading.
Those little coloured blobs are all too similar to me  

This was 100% pilsner malt, no water salt additions in 35 litres of Sydney (Prospect) water.
So I wouldt think the mash pH would be too high, with no darker acidic grains to bring the mash pH down.






Will do the conversion test again after the main mash to hopefully see the difference.

thanks
Bjorn


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## pk.sax (2/1/12)

Done it last 2 brews. Really handy since i'd switched from lagged stove top biab to unlagged keggle tun and wanted to see if I was doing it right. I take a drop of iodophor with my thermometer, put it in a white saucer and streak it across to spread. Then just put a few drops of wort on that. Worked exactly like you say. Also did a taste test, how sweet it tasted with good conversion. Not sure if it's something to go by but I think I had full conversion this last time after the first decoction.


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## mika (2/1/12)

Interesting BYO article recently where they were logging SG of the mash against the Iodine. SG continued to rise well after the Iodine test indicated the mash was done.


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## BjornJ (2/1/12)

main mash over, raising to mash-out now.

Did a iodine/starch test again:


First the saucer with some iodophor on it;



then dripping in some wort that was left to cool for a few minutes first;




No purple colour, if anything the combined liquid is clearer, no orange tint anymore.


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## HaveFun (18/5/19)

Hi,

is a starch conversion test useful when I do step mashing, after the first step?

I normally mash 35min at 63 degrees and 45min at 72 degrees. 

Cheers
Stefan


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## JDW81 (19/5/19)

If you're using well modified malts then you're going to get good conversion in that time, along with more conversion at 72C and ongoing conversion while you ramp your temps up to 72C (the upper limit of alpha amylase activity, but it doesn't denature until ~77C) so it probably isn't necessary. Having said that, a conversion test only takes a few minutes so doing one isn't really going to make that much difference to your brew day.

JD


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## HaveFun (19/5/19)

I just did a few tests and for me, it looks like that after 20 mins at 72C all starches are converted..

I'm doing 8kg plus grain bills that's why I use to do long mash times up to 140min. 

I hope with the starch conversion test I can reduce my mash times. 

Cheers and happy brewing

Stefan


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## JDW81 (19/5/19)

HaveFun said:


> I just did a few tests and for me, it looks like that after 20 mins at 72C all starches are converted..
> 
> I'm doing 8kg plus grain bills that's why I use to do long mash times up to 140min.
> 
> ...



Grain bill size shouldn't make a massive difference to conversion time (particularly on a home brew scale) as the enzyme to starch ratio remains the same.

I often mash up to 15kg of grain when making double batches and don't change my mash times.

You could do 30 minutes at both temps and I'd wager you'd still get appropriate conversion. 

JD


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## HaveFun (19/5/19)

What is the "enzyme to starch ratio"

I doing an 8-9kg grain bill to end up with around 35l wort enough for 2 corny kegs.

Thanks

Cheers
Stefan


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## MHB (19/5/19)

Really the important time is just before you mash-out, to make sure you haven't got any unconverted starch before you kill of most of the enzymes, which is one of the reasons for doing a mash-out.

Trying to shorten mash times can be a big mistake, even a wort that tests starch free can be very rich in dextrin's that still need reducing or you beer wont be what you are aiming for.
If being starch free was the only aim of mashing you could get that in 20 minutes at 75oC but your beer would be very sweet.
An Iodine test only tests for starch, it doesn't tell you to stop mashing.
140 minutes may be a bit excessive, the time spent ramping counts as mashing time. If you mashed in at say 60oC and heated to 80oC at 0.5oC/minute (40 minutes) you would be at about the bare minimum for all the enzymes to do their thing.
That would be at a high L:G (>5:1), exactly the right pH in a stirred mash of very finely milled grist, plenty of Calcium and trace elements... absolutely optimum conditions for conversion and extraction.
I usually mash for 60-90 minutes (total including ramp times).
Mark


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## JDW81 (19/5/19)

HaveFun said:


> What is the "enzyme to starch ratio"
> 
> I doing an 8-9kg grain bill to end up with around 35l wort enough for 2 corny kegs.
> 
> ...



Basically saying that 1 grain of malted barley has x amount of enzyme and y amount of starch/long chain sugars. 1000 grains of barley has 1000x amount of enzyme and 1000y amount of starch. The absolute values increases, but the ratio stays the same so the way the mash behaves doesn't change (all else being equal)

It's not a specific brewing term or concept or something that is really discussed, just using it to illustrate that on a home brew scale a bigger mash doesn't mean a longer mash time as it is the ratio of the 2 that matters, not the raw quantities.

JD


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