Yesterday I received a PM that was essentially asking how to work out where the sugars come from and go in the production of sweet liquor. The PM finished with...
The main error the questioner was making is an easy one to make; he was trying to find the answer to the above by weighing. Not only did he weigh the spent grain, he even dried it and weighed that as well.My foggy brain, cannot figure a way to measure the sweet liquor left in the spent grains.
The problem is that when you weigh spent grain, whether it be wet or dried, you are weighing a mixture of husk, other inert organic matter, sugar, and, if wet, water; there is no way to know what percentage of what you weighed is sugar.
Below I'm going to attempt to explain how you can work it out. A side-benefit of this is that some other tricky concepts can be explained along the way.
Two Batches Both Producing 23 Litres of Ambient Wort
Batch 1 produces Ambient Wort with a Specific Gravity of 1.040
Batch 2 produces Ambient Wort with a Specific Gravity of 1.080 To help with this explanation, I'm going to be using two example brews, one light beer and one heavy beer. I'll attach some BIABacus files however, those files simply show where the numbers come from in the following diagram... Unless you have two screens, I would strongly suggest that you print the above diagram.
Sugar in the Grist (Sugar In) The first column shows the weight of the grist, it's composition and it's volume. (Please note that the height of this and other columns are approximate as I drew the diagram in a spreadsheet and so have just gone to the closest '5' mark).
Amount of Space (Volume) that Crushed Grain Fills
Notice that 1000 grams of crushed grain does not occupy 1 L in volume. In reality, it's really a little more than double that. In other words, if I had drawn the diagram more accurately, Batch 1, after crushing, would occupy about 8L in space and Batch 2, 18 L. People often get this number mixed up with displacement which we'll look at later below. The only usefulness of knowing this bit of trivia is, if you are crushing 5 kgs of grain, you'll want to be using a bucket of about 15 L to comfortably collect your crushed grain (grist).
Composition of the Grist.
All brewing software, besides the BIABacus, asks the brewer to input the sugar values for each individual grain. Most times, the brewing software will come with a list of grains and that list will assign an average "specification" to that malt. This does not mean however that the grain you buy will actually match that average specification. There's also a lot of confusing terminology in grain specs - different countries and sometimes malsters within the same country, can use different terminology.
If you do by chance have the specs for your malt, you can enter these in Section Y of The BIABacus. Even if you do entetr individual malt specs in Section Y, you will rarely find much of a difference from the BIABacus default which is based on the average of many typical recipes. In other words...
The BIABacus default, as mentioned at the top of Section Y, assumes that a grain bill will contain 4% moisture by weight, 76.8% 'sugar' and 19.2% of inert material such as husks. This means, for example, that if we have a total grain bill of 3,488 grams, 2,679 grams of that weight will be the equivalent of pure sugar (0.768 * 3488).
Total Grist Weight
Via various calculations that are beyond the scope of this post, the BIABacus works out that if you want to end up with say 23 L of ambient wort with a specific gravity of 1.040, a grain bill of 3,488 grams will contain the right amount of 'sugar' to acheive this end result.
Water In the second column, we can see that even though, on both batches, our desired end result is 23 L of ambient wort (meaning the amount of wort after boiling and chilling in the kettle), the 1.080 gravity brew requires a little more water than the 1.040 gravity brew. This is due to the factor called "Liquor retained by grain."
You can think of the grain bill as being a bit like a sponge. Obviously if we dip a large sponge into a bucket of water and pull it out again, the bucket will be less full than if we did the same using a small sponge. To compensate for this effect, on larger grain bills we start with a bit more water than on smaller grain bills.
The BIABacus uses a default of around 0.4 L per kilogram of "Liquor Retained by Grain," but, this is an average from many different brewers using different systems. It is definitely not the same for every brewer unless they are using the same equipment and process. Here's an example...
Imagine two brewers making exactly the same beer but one is making four times the amount than the other. When the smaller batch brewer pulls their bag from the kettle, they'll be able to squeeze it quite well. The large batch brewer is going to be pulling a much larger bag of grain and are going to be far less successful at squeezing sweet liquor from the bag. It's a bit like wringing out a wet face washer as compared to a beach towel.
In this post, I'm sticking with the BIABacus default.
Combining the Grist and Liquor (Water) - Mashing Displacement
The first thing to notice here is how much the volume increases when we add the grist and water together. For example, on Batch 2, we are adding about 18 L in volume of grain (see section above) to 37.4 L of water, but, when they combine, the volume now occupied is not 55.4 L (37.4 + 18) but only 44.1 L. In other words, 18L of crushed grain does not displace 18 L of water.
The next question then often asked, especially for metric users who are used to the fact that 1 kilogram of water occupies 1 litre in space, is something like, "Well, if we are adding 8 kilograms of grist to 37.4 L of water, how come the mash volume is only 44.1 L instead of 45.4 L?"
The easiest way to understand that is to get back to the sponge analogy. If we had an impervious concrete block that occupied 8 L in space and added that to 37.4 L of water, then, we would end up occupying 45.4 L of space. But, if we added a dry sponge that was 8L in volume to 37.4 L of water, it would be hard to tell the differnce in before and after volumes as the sponge is mostly empty space. Our grain bill is a bit like a very dense sponge.
Exchanges During the Mash
The next part of the mash that can be confusing is that we often think that during the mash, the sugar in the grist is simply swapped over for water. Our brain is trying to see it as a simple, black and white process whereas, in reality, it's more grey. For example, in Batch 1 we saw that 670 grams of "rubbish" (husks etc) went into the mash and so, it's easy to think that 670 grams of the dried spent grain will also be rubbish but, this is not correct.
During the mash, some of the rubbish will become a part of the sweet liquor as does a percentage of the sugar. In other words, a whole lot of stuff gets blended in several proportions. If we pull our bag full of spent grain at the end of the mash and weigh it, all we know is the weight of the mixture. Even if we dry it, all the dried weight will tell us is the total weight of a mix of dirt, husks etc and unused sugar. (There are several other complications in this weight area but mentioning them will create confusion and easily lead anyone trying to learn this down a very wrong path).
In the next part, I'm going to explain what happens between the end of lautering (draining the bag) and the start of the boil but before doing so I'll quickly explain the first BIABacus file.
After the Lauter (Draining) The first thing to notice between the third and fourth column in our diagram is the reduction in volume once the lauter is complete (the bag is pulled and drained). We have already covered this "Liquor Retained by Grain" factor in the area in the "Water" section above.BIABacus File - Distribution of Sugars Part 1 Please download and open up the following BIABacus file...This file is set up for Batch 1 but, to change it to Batch 2, all you need to do is replace the 1.040 in Section C with 1.080.
This file will show you where all the numbers in the diagram came from.
The only other important thing to note is that, in Section W, I have over-ridden the BIABacus default for "Kettle to Fermentor Loss (KFL)" and set it to zero. This means that the "Volume into Fermentor (VIF)" in Section B becomes our "Volume of Ambient Wort (VAW)". The ability to be able to do this makes difficult concepts like this much easier to explain. Some of you already skilled with the BIABacus, will also be using this trick to investigate ambiguous recipes you come across.
The second thing, we've covered in the last main section "Exchanges During the Mash." To expand on that, it is very easy for a brewer wanting to know how much sugar is in the spent grain to focus on the volume difference between the mash and boil. For example, on Batch 1, the mash is 38.9L and 34.1 L goes into the boil. (I'll be pedantic here and do a quick convert of the 38.9 L mash temp volume to what it would be at boiling point... 38.9 * 1.02 = 39.7 L). It's easy to focus on the 5.6 L difference (38.9 - 34.1) but, that is the messy mixture we talked on earlier. That mixture will tell us nothing. Here's what does tell us something...
The thing to focus on here is that 34.1 L of sweet liquor @ 100 C and with a specific gravity of 1.028 was produced. From this basically pure liquid, as opposed to a messy mixture, we have all the information we need to tell how much 'pure' sugar we have in our sweet liquor.
There are many ways of doing the maths to determine how much sugar we have in our sweet liquor however, I'm going to show ou how to use the BIABacus to do it as it's fast and also automatically adjusts for the volume changes that occur through temperature.
Sugar Left in the Spent Grain (Sugar Lost) on Batch 1BIABacus File - Distribution of Sugars Part 2 Please download and open up the following BIABacus file...This file is set up for Batch 1 but, to change it to Batch 2, all you need to do is replace the 1.040 in Section C with 1.080.
In this file, there are two differences from the Part 1 file you downloaded above. Firstly, in Section X, I have over-ridden the default kettle efficiency and set it to 100%. Secondly, in Section Y, I have set the specs for our "grain" to the same as pure, completely dry, sugar.
Now on the bottom right hand side of Section C, you'll see 2,385 grams. Section K still shows 34.1 L Volume into the Boil (VIB) and Section M, still shows a Gravity into Boil (GIB) of 1.028.
What this means is that there is the equivalent of 2,385 grams of sugar in our kettle at the start of the boil and, there will also be the same 2,385 grams of sugar in our kettle at the end of the boil. As an analogy, if you took a mug of wort from the kettle at the start of the boil and another at the end of the boil and allowed them both to cool, the first mug might taste like it has 1.5 teaspoons of sugar in it whilst the second mug will taste more like 2 teaspoons (see Section M). The only difference between the two mugs is that some water has been evaporated off the second one.
(and it's relation to kettle efficiencies (EIB and EAW) On Batch 1, above we saw that there was the equivalent of 2,385 grams of sugar in the sweet liquor we collected for the boil. So, on Batch 1...
Our grist contained the equivalent of 2,679 grams of pure sugar. We managed to get 2,385 grams of that into our sweet liquor. In other words, 89% of the sugar in our grist ended up in the sweet liquor. That 89% is your kettle efficiency on that batch. (Note that in Section P of the BIABacus, estimated Efficiency into Boil (EIB) and Efficiency of Ambient Wort (EIW) are always identical. As explained in 'BIABacus File - Distribution of Sugars Part 2' above, the weight of sugar during the boil does not change.
If 2,385 grams of sugar from the original 2,679 grams ended up in the boil, this means that there will be 294 grams of sugar thrown out with the spent grain. Certainly nothing to worry about there.
Let's have a look at the wastage on Batch 2...
Sugar Left in the Spent Grain (Sugar Lost) on Batch 2
(and why the Kettle Efficiency is lower than Batch 1) The same logic and maths we used on Batch 1 above, also apply to Batch 2 with one big difference.
On Batch 1 our kettle efficiency was 89% so our unutilised sugar was only 11%.
On Batch 2 our kettle efficiency was 77% so our unutilised sugar was 23%.
As a matter of interest, on the same equipment as used for Batch 1 and 2, a massive beer of 1.100 gravity of ambient wort would result in the following...
A kettle efficiency of 71.1% so, unutilised sugar would be 28.9%, or, more importantly, the equivalent of 2,424 grams of pure sugar which is the equivalent of about 3500 grams of grain.
[For anyone wanting to test themselves by working out how I wrote the above paragraph, I'm going to attach the spreadsheet the diagram come from here as it may help you. ]
The pattern we can see is that the more gravity of ambient wort we want, the more wastage we get. The BIABacus is the only brewing "program" that recognises this fact of brewing. Here is another analogy that might help explain the logic behind this...
Get a 10 L bucket of really filthy water, mop your driveway or something , as we really want that bucket to be about 75% filth. Now, get a white towel and cut a third of it off. You'll now have one small towel and another one twice as big. Drop them both in the bucket of filthy water. Now, pull them both out and lay them out on your now clean driveway until they dry.
You now have a good approximation of a 1.040 grain bill and a 1.080 grain bill and we can get to the final point of this post...
In brewing, we don't have an endless supply of water we can wash our crushed grain with; in fact, we are very limited. There is actually only one way to increase the amount of water we can wash our grain with and that is by increasing our evaporation rate which, means we would have to extend our boil time and, even that, won't increase the amount of water we start with by much.
So, in brewing we are effectively stuck with washing an article of clothing in a single bucket. Grab two 5 gallon or 20 L buckets and fill them to 3/4 full of hot water. In one bucket place the small towel, in the other, the large one. Soak them, agitate them, do whatever you want...
The end result is that if you pull the towels, neither will be white but the smaller towel will be whiter than the larger one.
To Finish Up There is a lot to take in above, but, when you "get it," you'll know you've got it*.
A new all-grainer, who had not read anything anywhere else, will get the above much faster than others; it's actually all pretty simple and logical. They won't understand why more experienced members take some time to "get it."
What the newer brewer won't realise, is how hard it is to "unlearn" stuff we have learned elsewhere. Those members have been exposed to a battering of terribly confusing, contradictory or even incorrect information that is so easy to find. It took me years to get it and I was one of the few that even realised something was seriously wrong!
The above is probably attempt number 4,863 at trying to articulate the knowledge above. Luckily, quite a few members here either waded through my earlier attempts or worked it out on their own .
If you do understand the above, pat yourself on the back, as, at time of writing, you're at the cutting edge.
P.S. I'm going to ask this thread gets locked for a day or so. One big problem with the internet and forums is that it's way too easy to jump in with a spur of the moment question that might be relevant to you but just confuses everyone else. In other words, if you do have a question, just take your time, read the above a few times and, if you still have your question, take some time in writing it.