poor fermentation

[Greenfield]

Hello Everyone,

I am seeking advice on a fermentation issue I have been experiencing. I have now fermented two, 2000L batches with an initial Gravity of 1.07 of a bourbon style mash. Both times now the fermentation seems to be pretty much stopped (very low fizzing) after 5 days with a gravity of 1.02.

Some quick info, My water has been tested and seems to be really great. I am mashing with softened water and then adding gypsum to make up for the lost calcium. I am using redstar DADY yeast and am fermenting near the limit of 30C.

Not too sure what the issue could be, could it be that i am riding to close to the temp limit?? What kinds of final gravity are you guys seeing with all grain mash bills?

 

Thanks

 

[Greenfield]

Also, 0.147 Mg/L (ppm) is the amount of zinc in the water after the softener. not sure if this is what could cause the issues

 

Thanks

 

[rcornel]

Have you taken a pH reading? If low, you may have contamination.

5 days may be on the long end of ferm time as well.

What delta in spec grav were you calculating to get?

 

[Greenfield]

rcornel,

we had appx 200L of sour mash added during the water heat up prior to the dough in, this was around 5.5. what was unexpected however was that after mashing completed, prior to yeast pitch, the ph increased to 6.5 during the mashing process... didnt think this was a poor pH for the yeast regardless so i pitched anyways.

I was hoping to get the gravity closer to 1, I would be happy if I was able to ferment an 8% ABV mash but right now I am sitting below that. What is a reasonable expected all grain percentage? I was always assuming  8% is something that can be expected... maybe im wrong? Ive done test mashes and achieved full conversion so I know there there should be enough available sugar to get there.

 

Thanks

 

[Huffy2k]

Greenfield, I can commiserate.  We have been having very similar fermentation issues.  We're having trouble getting below 7 brix (we are achieving anywhere from 15 to 19 brix during mashing).  We are going to try to exceed the recommended pitch rate for our yeast in our next batch.  I'll be watching this thread for additional ideas.

[captnKB]

@Greenfield try lowing your PH a bit with citric acid. Starting with a PH of your water at 5 will help to ensure a healthy ferment. If you are fermenting on the grain. Try pulling a sample and filtering out the solids before you read gravity. dont forget to correct gravity for temperature when you read. if you have a healthy dose of yeast when you started your should have a gravity near 1.000 after 2.5-4 days.

@Huffy2k are you using a refractometer to read the finished Brix/gravity? 

[Greenfield]

@captnKB

Ok I will keep this in mind, will dropping fermentation temperature from 30C to 25C have a great effect? or do you think the problem is rooted on a pH/nutrient level.

 

I have attached my water results as well.

 

Thanks

[Huffy2k]

captnKB - yep, we are using a refractometer to measure brix/gravity (mine provides both readings).

[Greenfield]

how vigorously do you guys agitate the mash once the yeast is added? I just give it a good stir with the paddle, do you think it would need more? 

[Tom Lenerz]

What is your mashing procedure? It is just as likely as non-fermentables as it is under attenuation.

[Greenfield]

9 minutes ago, Tom Lenerz said:

What is your mashing procedure? It is just as likely as non-fermentables as it is under attenuation.

Hey Tom,

 

1. heat water and sour mash to strike temp of 96C (204F)

2. Dough in corn and rye (unmalted flour) and hold at 93C (200F) for 20 mins. small amount of hitempase used to prevent thickening

3. cool to 87C (188F) and hold for 45 mins (remaining hitempase is added)

4. cool to 71C (160F) and then heat is cut. here barley is added with amylo 300 enzyme and held for an hour where temperature will slowly drop to 65C (149)

5. yeast is started in 10x mass and then pitched after 30 mins

6. fermentation held at 30C (high end of yeast limit)

 

Mash bill is 60% corn flour, 35% rye flour, and 5% malted two-row.

 

Thanks

[Tom Lenerz]

For step 4 I'd try a lower temp right away (148 or 149) to give the malt's beta-amylase preference to the alpha-amylase. That could lower your finish gravity. Also could try more malt.

[rcornel]

I agree with Tom--

You don't want to be on the upper end of the malt activity limit, bring it down at least to below 155F (67C).

pH of 6.5 is too high for optimal yeast growth, you want this closer to 5-5.5, you should check what it currently is to make sure it hasn't dropped too low to be detrimental to yeast, especially with the lengthy fermentation.

Did you take pH reading when mash was hot or cooled? pH reading is also temperature dependent (as temperature cools, pH increases)

Theoretical %abv will be based on starch content and density, but you've done a test mash, so you know what is "physically possible".

Being on grain, you should have enough FAN for yeast health.

Temperatures near 30C will increase ferm rate, but encourage bacterial growth as well.

 

 

 

[Greenfield]

@rcornel

 

Thanks for the tips, I will for sure try both adjustments next time. I am still not fully convinced that changing pH and the rest temp will give me an extra 2% ABV on the fermentation end.

Is there anyone out there also doing a bourbon mash with kerry enzymes? what is your mashing procedure if you don't mind sharing. Also is there a way to know if your sugars are fermentable or not? (im assuming there isnt a way to test this)

Thanks

 

[Blakeson]

I would bet that pitching temperature is a great factor. I have had GREAT fermentation with different kinds of water profiles and PH levels ranging from 4.8-8.2. But right when I pitch yeast too warm (85f+) my fermentation will get stuck after 4 days around 1.020 or so. 

Drop the temp, pitch the yeast. You will see the temp rising over the next few days. You want to account for that. IE: High end range for yeast is 90f pitch at 80f and let it rise over the next few days. 

[Greenfield]

Thanks @Blakeson

Appreciate all the feedback, I think for the next batch I am going to make the following adjustments.

1. better pH

2. cooler pitch temp for yeast

3. considering eliminating the super high strike temp and just holding the corn at 188 rather than 200. do you think 188 will still have the same effect on corn gelat?

 

Thanks

[Blakeson]

3 minutes ago, Greenfield said:

 

 do you think 188 will still have the same effect on corn gelat?

Pretty Sure Corn Gelat is between 180-185. I bring our corn up to 181, kill the heat, and let starch conversion happen over about 40 mins. No problems. Less heat in is less heat you have to pull out. 

[rcornel]

I would maintain a higher cook temp for corn, and bring it down to 170-80F for rye addition (if separate addition is possible with current set-up)

[Roger]

You are killing your malt/enzymes  by adding it over 150. 

 

Also, you can't use a refractometer on your beer, once it has alcohol in it. Fine for the initial info, but worthless once the fermentation starts. 

 

[Scrounge]

Roger- you most certainly can use a refractometer after fermentation has started. You need to have the starting brix and do some math, or use one of the handy on-line calculators. Refractometer is the perfect tool for doing all your potential/actual abv with grain in.  Who wants to mess with hydrometer s in oatmeal. 

[Greenfield]

I have to agree with @Scrounge on this one. Also, @Roger our hitempase and amylase enzymes are rated for temperature above 150F so I have a hard time believing that is the issue.

 

I am doing another 2000L bourbon mash tomorrow, and Ill let everyone know if the changes have any affect on the FG.

 

Thanks

[rcornel]

Anxious to know the results! Good luck @Greenfield

[Roger]

I meant without the calculator. raw Refract doesn't work post ethanol without calculations.

 

[3d0g]

2 hours ago, Scrounge said:

Roger- you most certainly can use a refractometer after fermentation has started. You need to have the starting brix and do some math, or use one of the handy on-line calculators. Refractometer is the perfect tool for doing all your potential/actual abv with grain in.  Who wants to mess with hydrometer s in oatmeal. 

Ehhh, be careful. Those "handy on-line calculators" make a LOT of assumptions about wort composition. They're typically derived from regression of beer fermentation data. A distiller's grain bill (and fermentation) can be radically different resulting in several brix error.

[Scrounge]

3dog- what you say is true. You have to assume a wort correction factor that is in the formula, but it gives you a great indication of how far your fermentation went, based on what your starting brix was. Certainly better than a hydrometer in porridge!!!  Wouldn't you say?  That's how we roll around here anyhow.