I’m an advanced Nube, been involved with the craft since early teens and i have kids in college now. I’ve made quite a few batches of mash but never seen one like this...
Prep and Mash steps (for background info)
Its all corn, using cracked corn then home ground to corn meal, but not quite flour.
Used approx 45-50 lbs of corn, 20 gal of h20 at 200 F and PH @ 5.6-5.8, used 1/2 oz alpha amylase pre and post gelatinized stage at 180-185 F for 3 hrs. Worked good to keep mash thin to stir well.
Let set then added 5-7 gal h20 and stirred (bbq rotisserie stick w/ forks) and tell cooled to 150-155 F and added 5lbs hand shredded sweet potatoes to semi-cook them to release Beta Amylase, but also added 2 oz more of Alpha Amylase for initial and then secondary starch break up once taters released Beta-Amylase. Wrapped barrel and let set for 3 hours.
Stirred every hour and then had fan blow on barrel to help cool to approx 95 F. Added yeast bomb of 1.5 cup mash and 2 oz of Dadys yeast. Let triple in size, then adjusted mash barrel PH to 4.2-4.5 and pitched yeast, stirred w/ lots of aeration, added dozen large oyster shells, covered w/ tube to water for bubbler and wrapped to maintain temp...
Next day, bubbling good, lifted lid to take temp and found what could only be described as looks, smells, tastes like “Corn Oil” on top. Mash still thin, Temp still approx. 95-97F, PH is 4.3, and sampled SG found it at approx 1.04 (hard to test due to fine corn still suspended in mash. Gave it gentle mix then Covered and rewrapped.
Two days later (today) looked again and found it same temp/PH, but much more oil present. Skimmed most off and put in gallon jug.
Anyone have ideas what’s going on? Ive done many cracked corn only mashes, many sugar, TPW, and many mixed grain mashes, but Ive never seen any with ANY oil on top....