Ask Mr. Wizard

Starch Conversion

TroubleShooting

Bill Broderick • Newnan, Georgia asks,
Q

As I understand it, 100% mash efficiency on a brewers level is actually 80% due to grain hull mass and insoluble starches. So a mash that contains Pilsner malt having a maximum 37 possible gravity points per gallon, at 80% efficiency, would yield approximately 30 gravity points per gallon; a very efficient mash by most standards. If you achieve less than 100% of a brewer’s possible yield, are there not unconverted starches present in the beer that will cause a haze? Or are all the remaining starches insoluble? If you perform an iodine test for complete conversion, and the results show no remaining starches, and you have a mash efficiency of 70%, does that mean 30% of those starches are insoluble no matter what, or does it mean your specific mash regimen could not convert the remaining starches and they remain solid and not in suspension? Is the final product missing something without insoluble starches present to the point I should intentionally decrease my efficiency?  How will the wort from a mash tun that produces very high efficiencies with accepted normal water to grain volumes, grain crush, mash and sparge times, temperatures, pH, etc. compare to wort produced under the same parameters by a mash tun that is less efficient?

A

If you achieve less than 100% of a brewer’s possible yield, are there not unconverted starches present in the beer that will cause a haze? Or are all the remaining starches insoluble?

Response by Ashton Lewis.