Starch in the Brewing process
Does anyone know why it is that you can get negative starch conversion in the brewhouse and then see starch later on in the process? I have seen it at 2 breweries that I have worked in where no starch is indicated and then further upstream in the process there is starch indicated. In both of these situations heating problems caused the mashes to cook way too hat too soon and that was the reason for lack of conversion.
In one case an iodine stain of the wort/beer showed negative for starch until the fermentation was complete, and then indicated a purple starch positive. In another case the mash and first runnings showed negative for starch and then the last runnings showed positive for starch.
If anyone has an answer please let me know!
Quality Services Engineer, Miller Brewing
As you have discovered, the iodine / starch test is not perfect. I assume you are using a mash conversion vessel with mixer paddles and heating panels. Are you sure you are getting perfect mixing of the mash in the vessel, and are therefore not getting total mixing until transfer to lauter tun ?
The starch may be present & undetected but not washed out until the mash temperature has been raised by the sparge liquor to such a point that it is released from the grain - a lower sparge temperature may therefore help.
Are you sure it is starch and not glucans that are being detected ? These seem to take a while to combine to visible particles, I think as a result of pH drop during fermentation.
That is interesting about the glucans. In one of those cases that I outlined there were some major problems with beta-Glucans in the malt that lasted about 3 months. I doubt that is the current problem we are having with one of our brews, but that would definitely explain why we had a positive in prior instances at my former employer.
As far as the mash mxers there were no problems before with starch prior to these incidences, and they were looked at as a possible source of lack of conversion by the respective engineering departments. The temperatres were consistent throughout the mash.
Thanks for the input! It definitely helps me in trouble shooting.
One more question since you know a little about glucans. Will they form the same sort of ropes in the beer as starch? Will this result in the same fitration and yeast harvest problems? I am curious, because I am sure I will see glucan problems again in my carreer!
I have made a few enquiries. Several people have confirmed they too have experienced starch passing through to fermentation etc although not picked up in the mash vessel. This can happen at any time dependant upon the mash mixer operation, or in the case of a mash tun, simply because the very top (say 0.25 to 0.5 inch) of the mash always goes comparatively cold, and doesn't convert fully. Other instances have been traced to inconsistent malt modification. Changing the malt has resolved the problem. On reverting to the original malt, hey presto, the starch reappears. Additionally, there have been other reasons, not clearly identified, but thought to include mash liquor ionic composition and pH changes, and adjuncts not being pre cooked sufficiently.
We do not tend to suffer beta glucan problems with highly modified malts, but use additions of beta glucanase in the mash to help reduce the problem. High levels of beta glucans show up as slow runoffs, possibly set beds, poor extracts, and short filter run lengths due to blinding. Virtually no amount of powder seems to be able to alleviate effectively the impact of high glucan levels in beer, and the filter ends up with almost a "slime" on the filter bed, which is difficult to wash off. The glucan may also show up as "bits" or floaters in the final product, more so after pasteurisation which seems to allow or encourage coagulation of the smaller particles into visible particles. Inevitably, this appears to be worse in conditions of high PUs and or high in pack oxygens.
Hope this helps