Why so long?

[WikdWaze]

Here's a question that's been bouncing around my head for a while. Why does honey take so long to ferment? I know there are lots of possible explanations relating to nutrients and such, but my braggot really shines an interesting light on the subject. Many of you already know I did a split batch. Both batches contain the exact same ingredients, both received yeast from the same pack, both were pitched at the same time, and both have been exposed to the same environmental conditions. I pitched on the 14th, one batch has shown no activity since the 20th, and one is still going. The only difference between the two is the proportion of fermentables derived from honey. Both jugs have the same amount of total fermentables, about 4 pounds, but one has 75% honey and 25% malt extract while the other is split 50/50. The 50/50 batch is the one that has finished. This raises the question, what is it about honey that slows fermentation? These two batches are as identical as you could possibly make them except for the amount of honey. Why is one finished while the other is still going two days later?

 

[Jmattioli]

First of all, honey doesn't take so long to ferment. Typical liquid malt extract doesn't contain the same amount of fermentable sugar as honey. About 34 points gravity per lb in 1 gallon.

https://hoptech.com/index2.html?https://hoptech.com/extracts.html


You never took an accurate reading to start but the batch with 50/50 had a lower specific gravity. The extra gravity in the other will take a significant longer time cause as the yeast reaches near tolerance it slows down. I suspect you may not even have accurately measured your honey since you did not mix it in the original wort but rather added it to the jug later. (per your comments).
Fermentation time is not linear. The first few days is usually the fastest. As alcohol increases and nutrients decrease, it slows down.
This should answer your question.
Joe

 

[JoeM]

Honey also lowers the pH of the solution much more than malt does (although this will vary greatly depending on the acid and buffering content of the type of honey used). This could also contribute to the difference. However, i agree with Joe that most of the difference probably stems from the fact that 1 lb of honey simply does not equal 1 lb of malt extract, and as you pointed out there is probably a significant difference in the amount of nutrient. All these small difference may add up to a BIG difference.

 

[WikdWaze]

Hmmm, a combination of little things adding up to a major thing. Much like the compounding of loose tolerances adding up to a poorly constructed machine.


No, I did not measure the honey, per se. I did divide it into 5 equal parts, 3 into one jug and 2 into the other. It was supposed to be a 5# container, but who knows how accurate their weight was. This does not take into account the honey that was left in the various containers since I did not rinse them to get every last drop. There is no doubt the 75/25 batch had a higher SG, but we may never know how much higher. Myself, I don't think it would be more than a small percentage difference. There were a lot of components in this recipe that raised the SG which were equal between the two.


I honestly don't think nutrition played a role in this phenomenon. I know the malt contributed some nutrients, and reducing it would obviously reduce that contribution, but buckwheat is one of the most nutritious honeys available. It would seem that the buckwheat would make up for much of the difference. Also, the main source of nutrients in this recipe would have to be the wort, which is identical for both jugs. There was nearly half a gallon of wort in each gallon jug. That's a lot of nutrients. And even meads made with commercial nutrient take longer to ferment than your typical beer.


My personal belief is that pH was the major player in this. I need to find the study I read, but they tested the effects of pH on fermenting yeast. The results of the test showed that fermentation time was virtually uneffected by pH in the range of 4-6, but could as much as double if the pH dropped to 3.5. Given that the pH of honey averages around 3.9, adding more honey will put you closer to that from the start. And honey has a built-in mechanism to lower the pH if it rises.

 

[Jmattioli]

There is no doubt the 75/25 batch had a higher SG, but we may never know how much higher. Myself, I don't think it would be more than a small percentage difference. There were a lot of components in this recipe that raised the SG which were equal between the two.

It can be calulated to be around 15 points by your stated difference in honey versus malt. That is not insignificant.

I honestly don't think nutrition played a role in this phenomenon. I know the malt contributed some nutrients, and reducing it would obviously reduce that contribution, but buckwheat is one of the most nutritious honeys available. It would seem that the buckwheat would make up for much of the difference.

Buckwheat is still far lacking in nutrients (FAN) for fermentation. It happens to have more than other honeys but according to Ken's published data, it is still lacking by a significant amount. D47 yeast is not like K1V. Reference Lalvin information if you do not believe this. It requires a higher level of nutrients for a fast complete fermentation.

My personal belief is that pH was the major player in this. I need to find the study I read, but they tested the effects of pH on fermenting yeast. The results of the test showed that fermentation time was virtually uneffected by pH in the range of 4-6, but could as much as double if the pH dropped to 3.5. Given that the pH of honey averages around 3.9, adding more honey will put you closer to that from the start. And honey has a built-in mechanism to lower the pH if it rises.

That is true Wikd,
However, even the small difference of SG when you are approaching alcohol tolerance levels will make a difference in fermentation times. As I said fermentation is a non-linear curve and 15 points in SG can make a significant difference in time toward the end of fermentation especially when approaching tolerances which you are with the yeast you used. And if you measured correctly, that should have been close to the difference. As Joe M pointed out all were contributors. You can believe what you want but experience will show you that JoeM's analysis is more accurate than your comment. (thinking) There is a good possibility you are thinking inside the box again instead of considering all his points.
Joe

 

[WikdWaze]

I wasn't not considering points, I was merely providing counterpoints. That is, after all, how discussions work ;D I did in fact agree with pretty much everything posted in response to my question, with some qualifications.

I'll have to contact the malt manufacturer and see what percentage of fermentables are in that particular malt. I have a very hard time believing there would be a 15 point difference between these two batches. I'm not saying it's impossible, just that it seems unlikely to me. Also, a higher SG would be more likely to cause a slow start rather than a slow finish, and both batches were running even at the 6-hour mark.

As for nutrients, the reason I don't think that was really a contributing factor is because the honey and malt made up less than half the volume of the must. The oat/rye wort added nearly a half-gallon of milk-like liquid to each jug. I have absolutely no idea what all was in that wort, but there had to be a good deal of food for yeast to eat. Compared to that, the difference in nutritional value between a pound of honey and a pound of malt seems largely irrelevant.

I absolutely agree with the pH hypothesis.

 

[JoeM]

Also, a higher SG would be more likely to cause a slow start rather than a slow finish

This is not true. The only time a higher SG causes a slow start is if the wort is near or above the osmotic potential that the yeast can tolerate which is not the case here. Otherwise a higher SG will cause a slower finish because as the yeast finishes it comes closer and closer to its alcohol tolerance and fermentation drops off asymptotically as the yeast colony is slowly culled.

When the SG is lower fermentation starts off in an exponential fashion as it always does but the yeast run out of fermentable before they ever reach the asymptotic portion of the curve. instead of progressively slowing, fermentation just comes to a halt...in other words the yeast run out of food before coming anywhere near their alcohol tolerance so fermentation doesn’t slow it just stops.

JV

 

[David Baldwin]

As for nutrients, the reason I don't think that was really a contributing factor is because the honey and malt made up less than half the volume of the must. The oat/rye wort added nearly a half-gallon of milk-like liquid to each jug. I have absolutely no idea what all was in that wort, but there had to be a good deal of food for yeast to eat. Compared to that, the difference in nutritional value between a pound of honey and a pound of malt seems largely irrelevant.

Remember that it's not just chemistry but biochemistry that we are working with. Proper nutrition is as essential for our yeast as it is for us. Lots of fermentables does not necessarily mean lots of essential nutrients for healthy yeast.

You might be able to survive on a diet of snickers bars, but you'll never train for the olympics on that.

Of course some yeast strains will tolerate poorer nutrient levels than others will as well. Like people - some can tolerate different foods better than others. It's all in the genetics.


No flame intended here, and I hope none is taken. You are getting some excellent and experienced advice.

Without quantifiable data on your starting SG, it's going to be tough to make any irrefutable diagnosis.

Truly wishing you an awesome first experience!

 

[WikdWaze]

This is not true. The only time a higher SG causes a slow start is if the wort is near or above the osmotic potential that the yeast can tolerate which is not the case here. Otherwise a higher SG will cause a slower finish because as the yeast finishes it comes closer and closer to its alcohol tolerance and fermentation drops off asymptotically as the yeast colony is slowly culled.

When the SG is lower fermentation starts off in an exponential fashion as it always does but the yeast run out of fermentable before they ever reach the asymptotic portion of the curve. instead of progressively slowing, fermentation just comes to a halt...in other words the yeast run out of food before coming anywhere near their alcohol tolerance so fermentation doesn’t slow it just stops.

JV

Oops, I was misinformed. I had read somewhere that a high SG would make it hard for the yeast to get going. Still, in order for that to have been an issue, the 50/50 batch would have needed to have too little sugar to go to 14% ABV. According to the scale on my hydrometer that would require an SG of less than 1.110, which is not possible with nearly 4# of fermentables.

Posted by: David Baldwin Posted on: Today at 10:28am

Remember that it's not just chemistry but biochemistry that we are working with. Proper nutrition is as essential for our yeast as it is for us. Lots of fermentables does not necessarily mean lots of essential nutrients for healthy yeast.

You might be able to survive on a diet of snickers bars, but you'll never train for the olympics on that.

Of course some yeast strains will tolerate poorer nutrient levels than others will as well. Like people - some can tolerate different foods better than others. It's all in the genetics.


No flame intended here, and I hope none is taken. You are getting some excellent and experienced advice.

Without quantifiable data on your starting SG, it's going to be tough to make any irrefutable diagnosis.

Truly wishing you an awesome first experience!

I am well aware of the importance of nutrition. The point I was making is that there is almost no nutritional difference between the two batches. If the recipe was low in nutrients, it would be low in both batches and both batches would be effected by this. It can't possibly be nutrient-dense in one jug and low in nutrients in the other. There wasn't that big a difference between the two, all the ingredients came out of the same containers.


It will be a wonderful experience as soon as I get to actually drink it ;D

 

[David Baldwin]

Ah, ok I understand better now what you meant there.

 

[Jmattioli]

If the recipe was low in nutrients, it would be low in both batches and both batches would be effected by this. It can't possibly be nutrient-dense in one jug and low in nutrients in the other. There wasn't that big a difference between the two, all the ingredients came out of the same containers.

But again you are thinking inside the box. The nutrients might be the same though that is doubtful since malt has more than honey but irregardless, even if they were the same, the one with the higher SG may require more nutrients than the other to finish since it may go further. Hence nutrients can be a factor. You can research the link I posted above to see that the malt may be up to 14 points different ( or more). Some malts in fact are lower attentuation than others. (less fermentable sugars) The brew shop where you purchased it will tell you if you ask them. Mine carries low, medium and high attenuation malt extract.
Joe

 

[WikdWaze]

But again you are thinking inside the box. The nutrients might be the same though that is doubtful since malt has more than honey but irregardless, even if they were the same, the one with the higher SG may require more nutrients than the other to finish since it may go further. Hence nutrients can be a factor. You can research the link I posted above to see that the malt may be up to 14 points different ( or more). Some malts in fact are lower attentuation than others. (less fermentable sugars) The brew shop where you purchased it will tell you if you ask them. Mine carries low, medium and high attenuation malt extract.
Joe

I don't deny any of that. I can see how SG could effect the nutritional requirements of the yeast. You seem to be operating under the assumption that the only nutrients in the must came from the malt, I simply don't believe that. Yes, the 50/50 batch would be less fermentable and have more nutrients due to the higher concentration of malt. But even if the malt was only 50% fermentable there would still have been 3# of fermentables in that must, plenty to go to 14% ABV. So the yeast would hit their limit in both batches. And the difference in nutrient levels due to the difference in malt proportions would be more than compensated for by the presence of the nutrients in the wort. I don't see a pint of malt extract having more nutrients in it than nearly 2 quarts of wort.

 

[Jmattioli]

You seem to be operating under the assumption that the only nutrients in the must came from the malt, I simply don't believe that.

Not making that assumption here at all and never said that. I'm talking possibilities based on your ingredients. If everything was the same except the malt versus honey, it is a known fact that the one with the 2 lbs of malt had more nutrients. I never said one was deficient, only that the malt had more FAN and nutrients than the buckwheat. That is a researchable fact. There doesn't have to be a large difference to make a difference. D47 just loves FAN (Free Amino Nitrogen). Lalvin tells you this about the yeast. Malt has lots of it. Honey, very little. The wort was the same in both batches but there is definitly more FAN in the one. You have no accurate reading on the OG . Based on your observation my only statement is that the difference in starting SG, nutrients, and PH all have a contributing factor to the possibilty of one finishing before the other. You haven't indicated the final gravity of the one you say is finished. It may not be for all we know. Something could be wrong. It may not even be at alcohol tolerance. Check it and let us know more data. By your own admission, you made every mistake in the book. You started this thread with a good question. At least 3 individuals attempted to give you some insight. You don't have to agree with all or any of them but they were kind enough to pose some thoughts for consideration to your question. You don't have to debate them or disagree, just consider them and ask more questions if you don't understand their reasoning. Or let it slide if you can't see their point. After all, this is your first mead and you yet have much to learn as do we all including me.
Sincerely, Joe