Partial Boil - Extract Brewing

[Kevnlis]

TL showed us how to do a partial mash (or steeping grains). I thought I would post this formula used to calculate the amount of fermentables that should be used in a partial boil to make it easier to use Beersmith etc. to calculate your brew and also increaes efficiency of hop isomerisation (to a point). I know it is floating around in various forms and explanations, but when I posted the following to another forum it looked useful and I thought maybe you guys would appreciate it

x = volume of water you will boil, eg: 4Lt
y = batch volume, eg: 23LT
z = total amount of fermentable sugars to be used in the batch, eg 3 kilos
f = amount of fermentable sugars to be used in your boil, eg: 522g

f = (x/y)*z

So for a 4L boil and a 23L batch with 3 kilos of fermentables you divide 4 by 23 and get 0.174 multiplied by the total fermentables in the batch which is 3 kilos meaning you need to use 522g in the boil. Of course this will vary if you are using amounts of things that are not fully fermentable as in the following recipe:

Coopers Draught
1.5 kilo LLME
500g LDME
500g Dextrose

Different malts and sugars will yield different amounts of final solids so we can not assume 100% across the board.

Kit = 1.7 kilos of LLME which yields 78% to the batch or 1.326 kilos
LLME is another 1.5 kilos at 78% yielding 1.17 kilos
LDME at 95% yields 475g
Dex is 500g because it yields 100%

This gives us a total of 4.2 kilos of addition but only 3.471 kilos are yielded to the batch. So to do the maths properly we need to use the equation as follows:

f = (4/32)*3.471

f = 604g and if we use LDME in the boil (which I would recommend) and it yields 78% then we need to use 775g.

Hope this helps, and if anyone needs anything explained more clearly feel free to ask!

Kev

[gregb]

Worth a sticky? I thought so.

Cheers,
Greg

[warra48]

+ 1

[KEG]

it seems that you're saying that unfermentables in the boil make no difference to hop utilisation? are you sure? i didn't think the fermentability made a difference, more the gravity - fermentable or not.

correct me if i'm wrong.

[Kevnlis]

Yeah good call, I guess I muddied the waters a bit there. I will fix it up. Not sure what the yield is of Corn Syrup so I may just leave that out

[sidman]

thanks for the info , every bit helps when you are learning

[sidman]

d

[Kevnlis]

It is lucky for a home brewer of any length of time to have not had a bad beer. In fact I think bad beers are necessary to learn from. If I had not had horribly bad beers I would not know how to detect small amount of badness in my good beers

Now... blow jobs are a different story all together... I am sure there are bad ones... but I can see no benefit to them

I agree a few grams here and there is not a big deal. But if you are trying to clone a brew and all you have is a full batch boil AG recipe this will do a lot to get you on your way to hitting your target accurately!

[Trough Lolly]

it seems that you're saying that unfermentables in the boil make no difference to hop utilisation? are you sure? i didn't think the fermentability made a difference, more the gravity - fermentable or not.
correct me if i'm wrong.

...Not sure what the yield is of Corn Syrup so I may just leave that out

Hop utilisation is a function of several variables, including - boil duration, boil intensity and original (pre-boil) gravity of the wort to be boiled. Kev's formula is a ratio that effectively tells you to use half the sugars if you halve the boil volume, which appears to be good in theory. The problem with this formula is when you try to tweak the formula to take into account extraction efficiency of the sugars from the recipe ingredients. Sites including "How to Brew" and the Bodensatz website have good data on extraction efficiencies, which of course can vary from one brew setup to another - it's not accurate to say that we all routinely brew with 78% efficiency but I suspect the adjustments are made to try to normalise the ingredients against their all grain counterparts?...Corn Syrup adds dextrins, not fermentable sugars. It also adds substantially to the pre-boil gravity which must be taken into account when calculating your target bittering levels.

Cheers,
TL

P.S. According to Palmer; Dextrin malt at 85% extraction efficiency typically adds 28 points per pound per gallon in gravity. Maltodextrin powder adds approximately 40 points per pound per gallon. To convert to points per kilo per litre, multiply by 8.3454.

[dragonphoenix73]

I may have asked this question on another forum Kev...

But what about the amount of fermentables one gets from the steeped grains?

Do we include that into our calculations? If so, how do we know the yield, amount, etc?

I think from memory you (or it may have been Ed) mentioned that you kinda ingnore that, but used the steeped grain wort as the water you are boiling in anyway....

And here's another question:
To rinse or not to rinse? (the steeped grains that is - I seem to remember some controversy over this question once before....)

[rwh]

But what about the amount of fermentables one gets from the steeped grains?

Do we include that into our calculations? If so, how do we know the yield, amount, etc?

You need to include the speciality grain extract in your boil gravity calculations, however virtually all of the extract will be unfermentable. See: Nominal Malt Steeping Yields in Points/Pound/Gallon

To rinse or not to rinse? (the steeped grains that is - I seem to remember some controversy over this question once before....)

I rinse. Just watch your temps to avoid tannin extraction. Anything below 80°C should be fine.

[Kevnlis]

Further to rwh's great advice I will mention that the gravity of the steep will still have to be taken into account when calculating hop efficiencies. Just because the steeped extract is mostly unfermentable does not mean it will not change the way the alpha acids react in the boil.

To calculate the yield of a given grain I usually just check Beersmith.

I rinse, and see no reason not to. I think the reason it is sometimes advocated not to is the fear of the person extracting tannins like rwh said. As long as you keep track of the water temps you are using you will be alright.

[Trough Lolly]

Good point re hop efficiencies, Kev...

Cheers,
TL

[dragonphoenix73]

Hi Kev and all....

I've been playing with this now for several brews now, and I think its all working out nicely.

However in the last brew, and in the one I am about to embark on, I didn't actually 'steep' any grains - I did actually do a true partial mash. And that got me to thinking....

How do I work out how much of that wort needs to be added to with Extract to get the desired amount of malt to boil hops in (I think i'm talking about value 'f' in the given formula.

I'll give you an actual example....

500g Pilsener Galaxy grain
1500g flaked wheat
1500g Wheat LME
1500g Pale LME

I'm using Promash, and the extract total (based upon values already plugged into the software) is 3.18kg of fermentables (this is based upon % of yield).
So my formula would look like this:
(6/23) x 3.18 = 830g of malt to boil hops in.

Now its all well and good to measure out 830g of LME... but what if I want to use the wort I have created from the mini-mash of the grains? Ignoring evaporation, I have 6Lt of wort, but how do I know how much malt I have in there in order to use that to boil hops in?

OK, I realise in this example I have included flaked wheat, but this could be any amount of grain that requires mashing instead of merely steeping.....

[Kevnlis]

This is a bit sticky because we can not be sure how much of the flaked wheat will be converted. Galaxy is good stuff but I am not confident it will get through it all.

If you do get full conversion (suggest mashing at 63C until you have a negative iodine test) you can simply use the following formula:

500g Galaxy x 75% extract x 65% efficiency (this is the standard brewhouse efficiency for mini-mash).
1500g Flaked Wheat x ?% extract x 65% efficiency (this is a very conservative estimate, even if you do get full conversion it is not likely to be very efficient).

The sum of those two formulas will be the total extract in your 6L of wort, I am guessing it will be a bit higher than 830g. You can fix this by doing a larger boil, or simply making a larger wort and boiling part of it separate to the hops boil, making sure you get a good hot break.

Hope this is enough info, if you need any further help feel free to PM me.

PS: If you do use that recipe, you will need a good couple hands full of rice hulls

[dragonphoenix73]

PS: If you do use that recipe, you will need a good couple hands full of rice hulls

Oh really?! What will that do?

I'm aiming for a spicy Belgian Witbier (you know, the sort with the coriander seed and orange peel)....

Promash has an extract-% value for wheat, so I'll go with that. I did use 6L as an example. I'll take your advice on that and boil in a larger volume - I'm thinking somewhere close to 10L.

But please enlighten me regarding rice hulls.....

[Trough Lolly]

The rice hulls physical properties help avoid grainbed compaction that can lead to a stuck sparge.

Cheers,
TL

[dragonphoenix73]

Thanks Trough.....

I don't have this kind of set-up, so maybe I don't need to worry about it. I'm still a little old-fashioned/unequipped/lazy/poor and so just put my grains in a grain-bag and sit them in a pot whilst I keep the water at constant temp (I have devised an ingenious method using a clothes peg, an over-sized pot lid, and a very large wooden spoon......

[Kevnlis]

Thanks Trough.....

I don't have this kind of set-up, so maybe I don't need to worry about it. I'm still a little old-fashioned/unequipped/lazy/poor and so just put my grains in a grain-bag and sit them in a pot whilst I keep the water at constant temp (I have devised an ingenious method using a clothes peg, an over-sized pot lid, and a very large wooden spoon......

I really see no way you could successfully BIAB that much flaked wheat! You would need a good lauter tun with a nice slow run off in order to get a good result.

You can make an esky tun for something like $30-35 (depending on what you have available to you, less if you already own a suitable esky).

If you want to do a Belgian Wit beer, the easiest and most successful result I have had is to use a 50/50 ratio of Galaxy to Flaked Wheat (wheat bix) and lots of rice hulls

[Sathias]

I've been using Beersmith to work out a few Extract recipes and I was hoping I could get someone to confirm if I am thinking along the right lines. I've been brewing 20 litre batches but doing a 6 litre boil.

What I've been doing is first putting all the fermentables into Beersmith which I put in at the start of the boil, and set my boil volume. I then work out my hop additions to get around the right IBU. Once I have this right I add in the rest of the fermentables to work out the % alcohol.

Is this an ok method to use to approximate the right amounts of hops?