View Full Version : starch in run off

David Masa
03-18-2005, 01:17 PM
I have the following problem.
We are brewing lagers using european malt and brewing single decoction. I have found that the originaly negative iodine reaction turns to positive as sparging continuos. The finall mash temp is 165 F, the same is the sparging water. First wort and at the beginning of sparging the iodine is negative , but as the sparging progreses it turns to be positive and it gets worse and worse till the end of sparging. Run off is clear, saprging water temp is correct. I think the problem could be the milling, but I am not sure at all. Because our mill has damaged grooves on the rollers, there are always some whole garins and big chunks in the grist, and it can't be fixed by gap adjustment. I think that the starch from these particles could be dissolved slowly during sparging, and since the temperature in kettle is at the and of sparging higher than 172 F, it can't be converted by the wort enzymes in kettle. Does anyone has any experience with that? And also do you know what colour gives betaglucans with iodine?

Thanks a lot for any

Ted Briggs
03-21-2005, 07:29 AM
I think you are absolutly right. Poor milling leads to unconversion of starches that are only extracted by the higher temps of sparging. Also you are getting lower extraction efficency! The best solution is to repalce/fix your mill. Assuming at least 5% loss of extraction, figgure out how much $ you would save if you bought 5% less malt each year. I am shure this would quickly pay for the new mill!!! And beer quality would increase with less starches being sent into the boil.
IMHO you cant do a betaglucan specific test w/ iodine. If it turns black, there are alot of starches...

David Masa
03-21-2005, 10:28 AM
Ted thank you for confirmation of my explanation. I also think it makes sense. The extraction efficency is not so bad in fact. I am not suer how do you calculate it in US, but expressed in precent of the laboratory declared extract present in total gris, I am getting yeilds of 94-97 percent, depending on the beer type, which is not bad, but it should be a little higher considering decoction brewing.

Ted Briggs
03-23-2005, 09:14 AM
I caculate extraction efficency as the difference between the malt suppliers stated Course Grind As-IS verses the actual plato of my wort for that volume/grist. I am running in the low 80% so your system is great! I still think beer quaility must suffer from the bad crush though, and fixing that mill should still be a issue. Mayby if you contact the manufacture you can buy new rollers without replacing the whole mill??

04-20-2005, 03:19 PM
I have a thought that hole grains in the mash might result in a harshy flavour. I think that this harshy flavour comes from the husk when starch is converted to suger and goes through the uncurched grain during sparging. I think this effect is even more common if you use darker crystal and colour malts. Others says im wrong. Anyone elses comments please.