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Jun 08, 2022 View:

Rye fermentation yield

Hi All, 

We make a Rye whiskey with 10% wheat, 5% cararye, and 85% malted rye.  We love the flavor, but consistently fail to ferment to completion - FG is usually 1.007-1.008.  We do ferment to completion with several other mashbills (all-corn, bourbons, 4-grain whiskey, etc); we only struggle with Rye.  Our mash process looks like this:

 - wheat in with JZyme TAA (high temp alpha) at 175 for an hour

 - cool to 155; add cararye & malted Rye along with JZyme SGA (saccharification enzyme).  Hold at about 150 for 1hour. 

 - Cool to 85F, pitch yeast.

We run a fairly thick mash so our brix at yeast-pitch is 17-19, and ferment / distill on-grain so we don't worry about viscosity / lautering yield.  We maintain ferment pH between 4.5 & 3.8 (usually no intervention is needed). We've played with ferment temps, ranging from 90F to 82F doesn't seem to matter.  We played with adding yeast nutrients, with no effect.  Adjusting the saccharification hold time (up to 2.5 hours) & temp (145-160F) has no effect.  In all cases, the mash ferments very fast, but reaches 1.007-8 in about 60 hours then stops.   

Any suggestions for how we can squeeze the last 1-2% ethanol yield from our ferment?



19 brix is what... 1080?  I'd consider dropping your gravity to around 1050. Should ferment dry and much quicker.  I've always found high gravity ferments to be persnickety in terms of going dry.  I assume JZyme SGA is some type of glucoamylase which snips long chain dextrines into fermentable sugars?



Reply:48 minutes ago, indyspirits said:

The final gravity reading is not measuring sugars only. It is measuring all sorts of soluble compounds. In my experience rye has a lot of dissolved compounds that are not fermentable sugars, and I assume these also have something to do with the high viscosity. 1.008 could be as low as it is possible to go with rye. In my opinion each different grain will have a different original and final gravity. 


The cararye is malted to have sugar that is non-fermentable, so your fermentation is probably complete. Most beers with caramel malts finish higher than 1.007. If this is about making alcohol and increasing yield, swap the cararye for something cheaper that converts. If you are happy with the flavor you are getting, note that it probably will have an impact on that.

Reply:14 hours ago, PeteB said:
Reply:4 minutes ago, klattig said:
Reply:3 minutes ago, kkbodine said:

It's nice to have all these numbers, like OG , FG, OHMY , etc but the real issue is: how much alcohol are you getting, from the total amount of grain (carbohydrate portion)?  

Are you finding a big difference between your various mash bills, or is this particular mash the only one showing less (based on carb content ) ?



What is the PG to bushel yield of the stripping run?

Reply:On 11/22/2018 at 2:12 AM, klattig said:
Reply:On 11/26/2018 at 10:19 AM, Julius said:
Reply:26 minutes ago, klattig said:
Reply:22 hours ago, ErictheRed said:

Sounds to me like your pH might be getting too low during the ferment?