Mashing cracked corn

[Tennessee_Spirits]

I've been trying to improve my mashing of corn for over a year and have gotten to about 60% efficiency and I'm interested in learning how to improve that to 75-80%. I have an insulated 15 gallon mash tun. Initial efforts showed little recovery with static mashing after boiling water and adding milled cracked corn. Specific gravity showed recovery of 20% or less even with the use of SEBStar Htl. This was a year ago. I made up the SG with sugar. My goal is high quality all grain spirits.

So about 6 months ago I bought a RIMs heater and started to enjoy the clearing of the mash and ease of holding mash temperature. I studied water salts and pH and optimized those. Frequent testing of specific gravity during mashing lead to longer corn treatment of 3 hours. SG leveled at this stage was 1.055 at 185 F. I tried 4 hour recirculation but that did not raise SG further. The alpha amylase was shown to make dextrins.

I got a better grain mill as corn is difficult to get a good grist in beer making grain mills.

I cooled the first stage mash to 150 F and added milled malt and glucoamylase so there was an excess of enzyme and increased this second stage mash to 90 minutes as SG kept rising for about 75 minutes at this temperature to 1.075 for this first running.

I tried increasing the amount of grist corn to 40 pounds but got a couple of stuck sparges and backed to 35 lbs then 30 lbs corn, 8 lbs malted barley and 3 lbs flaked rye for flavor. This reduction in grain actually improved recovery. I started sparging a gallon at a time and measured SG of the sparge and found it falling to 1.050 at 5 gallons sparge. The goal was a 10 gallon batch.

I next upgraded sparging and tried a sparge ring and tried the Blickman autosparge. Neither of these have helped so far. But having 6 gallons of 170F water and a Grant kettle has improved the process. I now get 5 gallons of first running and 5 gallons of sparging. The pre-boil SG is typically 1.060-1.065 of clear sweet mash. Total volume is 10 gallons and it ferments well with no cane sugar. It is too early to evaluate taste of finished product.

But calculations show that I'm getting 16.6 lb of sugar from mostly the corn with a grain bill above. Corn is about 80% starch. 30 lbs of corn could yield as high as 24 lbs of sugar but a realistic 80% efficiency would yield 19.2 pounds and I'm adding the barley. And the whole mashing is 5 hours including 30 minutes to cool and restabilize the temperature and add grain in the second stage. So far shortening the mash process lowers the gravity.

I noticed that George Duncan ran a video that said basically that you can't mash cracked corn at home. I am doing it but need ideas on how to improve the efficiency. So far it is making a pretty beer of about 8% ABV