New way to calculate FG, what do you think?

[lovelldr]

So I'm more and more tending to think that this forum just isn't for me at all.

Don't feel like that matey... The whole point of forums is to discuss things! You may not have the same pov as another, but you may well get others on to wondering whether you have a good valid point or not...

You may even be wrong, and someone come back with a full explanation as to why...

All comes down to different people's personalities and clashes, which is what also makes for the best discussions

 

[Aleman]

Does mash temp have an effect on the degree of fermentables/unfermentable sugars?

Quite simply yes. There are two enzymes involved. Beta amylase produces maltose and glucose and is effective over the range 60-66C, alpha amylase chops starch up into smaller units that beta amylase chops up further, its effective temperature range is 65-72C.

Once they get above their max temp they do continue working, but they are also broken down more rapidly . . . They are also broken down at their 'working' temp as well but that is another story.

So if you mash cool you get a more fermentable wort, if you mash warm you get a less fermentable wort. the temperature at any given point in the mash can be wildly different to a point elsewhere, we do try to get a uniform temperature distribution . . . but. Then what happens if you compile the recipe for 64C but through an error you hit 68C instead . . . you take action and reduce the temp but how do you account for the difference and duration that the mash spent not at the 'correct' temperature.

Even in the computer controlled brew houses that I have worked in, we formulated a recipe, and calculated the FG based on that 75% conversion ratio. . . . In fact we actually used the figures of conversion and fermentability from congress mashes that the lab used to do with each new batch of ingredients . . . but as 70-100% of the ingredients were base malt which will as near as damn it be 75% fermentable, the roughly calculated figure was good enough . . . And a FFT was performed to find out what it really would be.

 

[ScottM]

Don't feel like that matey... The whole point of forums is to discuss things! You may not have the same pov as another, but you may well get others on to wondering whether you have a good valid point or not...

You may even be wrong, and someone come back with a full explanation as to why...

All comes down to different people's personalities and clashes, which is what also makes for the best discussions

Oh don't get me wrong, I love a debate and a discussion.... in fact I love nothing more as this is the reason that I spend a lot of time on discussion boards and always actively try to get myself involved. I've been a member on many forums over the years, some good experiences and some bad, this one is certainly a mixed bag for me from what I've experienced so far but it's rapidly declining towards bad.

There just seems to be no interest in what other people have to say, especially when it isn't AG related (there's an obvious snobbery here in that regard too), and people want to talk a LOT more than they want to listen or even respond to anything that isn't centered around them. Check out the amount of questions in the various threads and check out the amount of responses those people asking the questions have to other peoples threads. It's very much a leeching society from what I have seen with a core of members who actually contribute (contributions are a mixed bag too). I don't know what it is, it's maybe an age thing but the best way I could describe it is grumpy lol. I find myself getting grumpier as I get older so perhaps homebrewing is more of a mature hobby thus meaning the members are naturally more grumpy than what I have experienced in other places.

Take this thread as an example. Has anyone even said anything remotely constructive about the subject? IMO it's all massively pessimistic and negative and opitimises a lot of my experience on here.... grumpy lol.

Most of my positive experiences have been from reading previous posts and how-to's, which is a bit of a shame really. I can definitely see why there is such a high turnover of members and stale accounts though, if you're not into AG and don't just sit down and shut up you are made to feel a little unwelcome.

Does mash temp have an effect on the degree of fermentables/unfermentable sugars?

Quite simply yes. There are two enzymes involved. Beta amylase produces maltose and glucose and is effective over the range 60-66C, alpha amylase chops starch up into smaller units that beta amylase chops up further, its effective temperature range is 65-72C.

Once they get above their max temp they do continue working, but they are also broken down more rapidly . . . They are also broken down at their 'working' temp as well but that is another story.

So if you mash cool you get a more fermentable wort, if you mash warm you get a less fermentable wort. the temperature at any given point in the mash can be wildly different to a point elsewhere, we do try to get a uniform temperature distribution . . . but. Then what happens if you compile the recipe for 64C but through an error you hit 68C instead . . . you take action and reduce the temp but how do you account for the difference and duration that the mash spent not at the 'correct' temperature.

Even in the computer controlled brew houses that I have worked in, we formulated a recipe, and calculated the FG based on that 75% conversion ratio. . . . In fact we actually used the figures of conversion and fermentability from congress mashes that the lab used to do with each new batch of ingredients . . . but as 70-100% of the ingredients were base malt which will as near as damn it be 75% fermentable, the roughly calculated figure was good enough . . . And a FFT was performed to find out what it really would be.

Great post, very informative.

I totally agree that the 75% calculation, for the most part, is good enough. I just did this because I wanted to get something more accurate, for no other reason than a bit of an exercise and to keep my brain active for a while. I have made a little program and I thought that if I'm going to use a calculation I should make it as accurate as possible, the whole idea with the program was just for something to do as well, as there are plenty of online programs for doing this.

 

[rich27500]

Well I found it interesting. If we're talking figures go by how many people viewed your post rather than replies. Lots of people will be interested without passing comment. Also if it works for you keep doing it, it's your beer you don't need approval from others.

 

[alanywiseman.]

I have been following your posts with interest Scott but have reframed from posting as it is not really something that I am too concerned about. But I think the problem that you are going to have with trying to get it as accurate as you seem to want it to be is the Hugh number of varibles.

I brew kit at the moment. The FGs I have reached for a number of brews have not been the same as others e.g. My wherry seems to have finished at 1.014 where someone stated the other day there's got to 1.006. Why is thre the difference? From my limited knowledge the freshness of the yeast, fermentation temps, water source, aeration of wort pre pitching....

You can not account for all of these and how they will affect the fermentation of your beer. Saying that maybe I am missing something and these will not affect what your trying to do? Just my thoughts anyway :thumb:

 

[ScottM]

I have been following your posts with interest Scott but have reframed from posting as it is not really something that I am too concerned about. But I think the problem that you are going to have with trying to get it as accurate as you seem to want it to be is the Hugh number of varibles.

I brew kit at the moment. The FGs I have reached for a number of brews have not been the same as others e.g. My wherry seems to have finished at 1.014 where someone stated the other day there's got to 1.006. Why is thre the difference? From my limited knowledge the freshness of the yeast, fermentation temps, water source, aeration of wort pre pitching....

You can not account for all of these and how they will affect the fermentation of your beer. Saying that maybe I am missing something and these will not affect what your trying to do? Just my thoughts anyway :thumb:

Basically calculating the FG would only let you know what would be possible given the perfect conditions. Anything that changes the conditions to anything other than optimal will change the FG.

Do you not think it would be nice to know what the FG should be, and then you could try to change your methods if you weren't reaching it?

The calculator I've made doesn't tell me what FG I will get, it simply lets me know what FG I can get based on the ingredients I am using :)

 

[ScottM]

Well I found it interesting. If we're talking figures go by how many people viewed your post rather than replies. Lots of people will be interested without passing comment. Also if it works for you keep doing it, it's your beer you don't need approval from others.

Oh yeah I definitely will. I don't think I'll hit the FGs that I calculate but it's always nice to know what the target is given optimum conditions.

Cheers :)

 

[alanywiseman.]

Basically calculating the FG would only let you know what would be possible given the perfect conditions. Anything that changes the conditions to anything other than optimal will change the FG.

Do you not think it would be nice to know what the FG should be, and then you could try to change your methods if you weren't reaching it?

The calculator I've made doesn't tell me what FG I will get, it simply lets me know what FG I can get based on the ingredients I am using :)

I see where you are coming from. It would be nice but i know that my conditions are far from optimal. If i had a fermetation fridge where I could control the tempp better then I would be well up for trying it out but at the moment i have a wardrobe in the spare room :lol:

So your yourself how long would you wait for a brew to get to the calculated FG? I have had a couple of brews that have been stable over 3 days but then droped a point or 2 after that?

 

[ScottM]

Basically calculating the FG would only let you know what would be possible given the perfect conditions. Anything that changes the conditions to anything other than optimal will change the FG.

Do you not think it would be nice to know what the FG should be, and then you could try to change your methods if you weren't reaching it?

The calculator I've made doesn't tell me what FG I will get, it simply lets me know what FG I can get based on the ingredients I am using :)

I see where you are coming from. It would be nice but i know that my conditions are far from optimal. If i had a fermetation fridge where I could control the tempp better then I would be well up for trying it out but at the moment i have a wardrobe in the spare room :lol:

So your yourself how long would you wait for a brew to get to the calculated FG? I have had a couple of brews that have been stable over 3 days but then droped a point or 2 after that?

I just wing it too. My beer is up the loft just now and I have a Ribena Wine in the kitchen fermenting at the moment with no temp control. My first WOW dropped to 0.991, so that's around 0.001 off the norm as far as I know, which would suggest my setup didn't have that much of a bearing on it

I always leave my brews in the primary for a fortnight before transferring to a secondary for another week. If it's not done after that little lot then I've done something very wrong. My temps are never under 18 degrees and being in Scotland they are rarely over 22.

However, I've only just started venturing into TC, wine and extract brewing so it's all a bit of a guess for me just now. I'm just going to take readings and write everything down to compare to my calculations. The Ribena wine is the first one that I took a lot of info on. My calculator predicted 1.102 based on the ingredients and the actual OG is 1.104. The reason for this is the additional solids in the ribena and grape juice. This means that my calculator won't actually be accurate at calculating OG for wines & ciders till I know exactly what solids are in what juice. The FG is obviously an offshoot of the OG and it's potential so I have a feeling my predicted FG might be a little bit off too as it suggested 0.988 is the potential, whereas I think it'll be around 0.990-0.992 if I take account of the difference in OG and the more unfermentables I have added (3 bottles of juice as opposed to 2).

Gives me something to do though eh

 

[StubbsPKS]

I just did this because I wanted to get something more accurate, for no other reason than a bit of an exercise and to keep my brain active for a while. I have made a little program and I thought that if I'm going to use a calculation I should make it as accurate as possible, the whole idea with the program was just for something to do as well, as there are plenty of online programs for doing this.

I can appreciate doing work like this as something to do that makes you think, but I also realize that most people won't be all that interested in the outcome. Most people use calculators or spreadsheets or tools written by others because they don't care about the math behind it so long as it's reasonably accurate.

Anyway, back to the topic, I'd love to see the results of brewing your example recipes and see how much more accurate your formula is :) I don't really brew kits that often, but I might be interested in an AG version of it provided that figuring out the variables based on the ingredients isn't insanely time consuming as my brew days are long enough as it is :rofl:

 

[ScottM]

I just did this because I wanted to get something more accurate, for no other reason than a bit of an exercise and to keep my brain active for a while. I have made a little program and I thought that if I'm going to use a calculation I should make it as accurate as possible, the whole idea with the program was just for something to do as well, as there are plenty of online programs for doing this.

I can appreciate doing work like this as something to do that makes you think, but I also realize that most people won't be all that interested in the outcome. Most people use calculators or spreadsheets or tools written by others because they don't care about the math behind it so long as it's reasonably accurate.

Anyway, back to the topic, I'd love to see the results of brewing your example recipes and see how much more accurate your formula is :) I don't really brew kits that often, but I might be interested in an AG version of it provided that figuring out the variables based on the ingredients isn't insanely time consuming as my brew days are long enough as it is :rofl:

It's very much a WIP at the moment but I'm hoping to tweak it for proper accuracy over the next few brews :)

My first proper test subject is the wine that I have on the go at the moment.

 

[ScottM]

Here's what I have so far. I need to measure the grape and ribena juices separately to find out what's missing, and obviously I'll need to measure the FG once it's done :)

Most of the sheet is filled in automatically based on a few user inputs.

 

[artiums_enteri]

Is this because OG (X3) -FG got boring?

I understand where you are coming from, but I should know my FG before I even put flame to kettle.

I know my pre-boil gravity + my kettle volume after a 60-120 minute boil I'm left with X amount of wort in the kettle. At 30 minutes into my boil my gravity must be Y or I need to make an adjustment to bring either the gravity up or the volume down. By the end of my boil there is no reason X and Y should not be what I have calculated the night before. Now I know for a fact that X = 7 gallons and Y = 1.075. I should also know from research, experience, and the company's publication that the yeast strain I'm using will attenuate down to Z. However, it will only attenuate down to Z at proper temp, accurate pitch rate, and appropriate amount of O2 added to the wort. I already have these figures noted prior to brewing because I've gone to www.mrmalty.com and gotten my pitch rate and the company's website told me how much ppm O2 I need to inoculate with. I have a healthy yeast starter, my O2 has been added, and now I pitch a starter of 3 smack packs in a 2 L starter which was in a stir plate for 18 hours. For this strain and a wort of 1.075 I need 200 ppm O2. With my regulator and stone that is 30 seconds of dissolving O2 into the wort. Given the data I had before my brew day I know that 1.075 (X3) -1.019 is my abv. I know 1.019 will be my FG because I've succeeded in all other variables. Now it's time to brew.

Some people ask, "what if Y is not what you planned on paper? Then the FG won't be right." wrong, I control Y at the end of the sparge by either boiling an extra hour to drop points, adding a pound of DME to bring up my points, and by just knowing my system. I brew once a week, and in the past year I've missed my numbers once. My pre-boil OG was 10 points low because I introduced a new sparge arm and float switch to the system. By adding 1.5 pounds of DME at the last 15 minutes of the boil my OG was exactly what I had planned, therefore my FG will be what I have calculated. Now granted, you can not allow a stuck fermentation or an immature attenuation, but that goes back to knowing your system and process.

 

[ScottM]

Is this because OG (X3) -FG got boring?

I understand where you are coming from, but I should know my FG before I even put flame to kettle.

I know my pre-boil gravity + my kettle volume after a 60-120 minute boil I'm left with X amount of wort in the kettle. At 30 minutes into my boil my gravity must be Y or I need to make an adjustment to bring either the gravity up or the volume down. By the end of my boil there is no reason X and Y should not be what I have calculated the night before. Now I know for a fact that X = 7 gallons and Y = 1.075. I should also know from research, experience, and the company's publication that the yeast strain I'm using will attenuate down to Z. However, it will only attenuate down to Z at proper temp, accurate pitch rate, and appropriate amount of O2 added to the wort. I already have these figures noted prior to brewing because I've gone to http://www.mrmalty.com and gotten my pitch rate and the company's website told me how much ppm O2 I need to inoculate with. I have a healthy yeast starter, my O2 has been added, and now I pitch a starter of 3 smack packs in a 2 L starter which was in a stir plate for 18 hours. For this strain and a wort of 1.075 I need 200 ppm O2. With my regulator and stone that is 30 seconds of dissolving O2 into the wort. Given the data I had before my brew day I know that 1.075 (X3) -1.019 is my abv. I know 1.019 will be my FG because I've succeeded in all other variables. Now it's time to brew.

Some people ask, "what if Y is not what you planned on paper? Then the FG won't be right." wrong, I control Y at the end of the sparge by either boiling an extra hour to drop points, adding a pound of DME to bring up my points, and by just knowing my system. I brew once a week, and in the past year I've missed my numbers once. My pre-boil OG was 10 points low because I introduced a new sparge arm and float switch to the system. By adding 1.5 pounds of DME at the last 15 minutes of the boil my OG was exactly what I had planned, therefore my FG will be what I have calculated. Now granted, you can not allow a stuck fermentation or an immature attenuation, but that goes back to knowing your system and process.

Where did you get 1.019 from though? You said experience and research. I was looking for a far simpler way of doing this on the fly, with no experience or research required. I'm doing all my research just now in the hope that I can from then on accurately predict the FG of any recipe I should wish to create.

I haven't done any recipes more than once and I've only done 1 extract recipe, so I don't have any real experience. Working hard on the FG calculation has put me within 1 point of the actual FG on my first attempt, so it would appear I may be onto something. That was just by chance though, really, as I actually started on the FG calculation for my WOW and Ciders. As all FG calculators I have found don't take account of going below 1.000 and they certainly don't take account of anything fermenting past 75%... even when the solids in the recipe are 100% fermentable (juice with sugar, for wine).

The %attenuation of the yeast is what I am querying. It doesn't take account of any changes in the fermentables. For example if you made an extract recipe with extra light DME and a comparible recipe with extra dark DME, if you used the same yeast strain and thus the same attentuation both would predict the same FG. Everyone knows that this would not be the case as there are a lot more fermentables in the extra light DME. My adjusted calculation takes into account the yeast attenuation value as well as the ingredients fermentables value.

As said, it's probably a lot more complicated for AG brewers but if you can get a hold of what's in your wort then the principle is exactly the same.

All WIP but I'm getting there with it.

 

[artiums_enteri]

I can understand what you are saying. My point is a brewer should know what all of his variables are before he brews. It's not hard to figure out your FG prior to brewing. Ibrew master, pro mash, beer smith, they all do this, and if you follow the correct formulas while brewing you will know what your FG will be. The brewing software I use on my iPhone/iPad is always within 1 point of my FG but only if my other variables have been met. The old fashioned way of doing this was to research the yeast prior to using it. Typically when I brew a brand new recipe or use a new yeast strain I'm looking at 2-6 months of research before I even put these ingredients together. Brewing a 20 gallon batch and tying up conicals and a brite tank is not cost effective, business smart, or efficient if I am not 100% sure what my end result will be.

I know my FG because I know my OG. Depending on the Sacchrmyces strains I know the yeast can only possibly attenuate down to a certain alcohol percentage before the yeast gets stressed and dies in its own byproduct. This information can easily be obtained from the yeast labs's publication. Also I'm looking at how high a flocculater this strain is and what the lab specs on attenuation per 500 billion cells is. Armed with that knowledge I know that if I make an RIS that is an OG of 1.112 my FG has to be 1.030 because the yeast I use for that beer (Scottish wee heavy) can't perform past 9.2%. No matter how much yeast I pitch it's not going to go any lower. I still have 20 points of fermentables in my beer, but short of adding another strain capable of drying the beer out and living in a toxic environment, I'm staying at 9.2. This is right on target for BJCP guidelines for the style. If the beer is dried out beyond its FG it won't be judged well, nor will it be to style. I also know if it drops below the FG it's a good chance I've gotten a bacteria in the beer which has continued to ferment those more complex chains.

Like I said even inexperienced brewers should know what their numbers are going to be within 1-2 points by both reading the literature on the yeast strain and the use of your favorite brewing software.

As for the attenuation of DME vs dark malt extract, they are actually the same pound for pound. DME is a condensed extract with the same amount of fermentable sugars as dark liquid. The only difference being the dark liquid has been mashed with dark grains by the maltster which adds nothing for conversion. The same amount of base malt was used by the company to create both products. A good example is this: if I make a yeast starter with 2L of water, 1.5 cups DME and 2 packets of 1056 the OG will be 1.045. If I make a yeast starter with dark malt extract at 1.5 cups, 2L of water, and 2 packs of 1.056 my OG is 1.045. Both will attenuate to 1.008.

 

[Baz Chaz]

I know you're probably enjoying the challenge you've set yourselves, going into such detail .......... but I'm bloody glad I didn't read this before I started brewing, I might never have started :wha: :lol:

Still an interesting read though

 

[ScottM]

As for the attenuation of DME vs dark malt extract, they are actually the same pound for pound. DME is a condensed extract with the same amount of fermentable sugars as dark liquid. The only difference being the dark liquid has been mashed with dark grains by the maltster which adds nothing for conversion. The same amount of base malt was used by the company to create both products. A good example is this: if I make a yeast starter with 2L of water, 1.5 cups DME and 2 packets of 1056 the OG will be 1.045. If I make a yeast starter with dark malt extract at 1.5 cups, 2L of water, and 2 packs of 1.056 my OG is 1.045. Both will attenuate to 1.008.

I know what you are saying, and I know this is the route that most people follow. However, in this part that I have quoted I don't think you have followed what I'm saying. They are both DME, I'm talking about the different amount of fermentables in extra light DME vs the amount of fermentables in extra dark DME. They are both condensed products made with different grains AFAIK. From what I understand extra light DME is made up of approx 80% fermentables and extra dark DME is made up of approx 70% fermentables.

The calculators, programs, sites, etc etc don't take these changes into consideration. They only take into account the yeast and its attentuation.

This isn't really much of an issue when it comes to AG as you will be making the wort on the fly and, as explained to me earlier, the amount of fermentables is adjusted via the temperatures. If following an AG recipe to the letter the FG should be known before you start... but the FG calculation to estimate it will be based on the attenuation of the yeast, rather than the actual amount of fermentables in the wort. By this I mean you could follow an extract recipe to the letter and you could then do the extract recipe again only changing the extract from say extra light to extra dark. The result would be a higher FG, but the calculators on offer wouldn't take this change into account.

A simple example of this is to use any of the FG calculators/programs etc to calculate the FG of WOW. None of them will throw out anything below 1.000, as they don't take any account of the additional fermentables (almost 100% in a wine). Depending on the WOW 0.985 doesn't seem impossible.