Ask Mr Wizard Converting starches Q I used a recipe calling for eight pounds of British pale two-row, one pound of carapils, and some crystal and chocolate malts. I am using a step mash: 30 minutes at 126° F, 15 minutes at 140° F, one hour at 154° F, and five minutes at 168° F. After the 15-minute beta amylase step at 140° F, I took a sample just for kicks and ran the iodine test; it showed no starch! This was before my 154° F conversion rest. How can all the starch be converted to sugars this soon? And if it is, why bother with the one-hour conversion rest? A One of the most important aspects of measuring anything is to understand what is being measured and how the measuring device works. The iodine test indicates the interaction between iodine and the alpha-helices of amylose starch (amylose is the unbranched form of starch, and amylopectin is the branched form). This interaction causes an absorption of light resulting in a blue-black color. A negative iodine test indicates the absence of large amylose molecules, but it does not by default indicate the presence of fermentable sugars. Read More |
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