Tinseth Formula

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Tinseth Formula

Postby robert4136 » Sat Feb 21, 2009 10:57 am

I have been experimenting recently with the different hop utilization formulas, particularly with the Tinseth formula.

given a certain recipe, i get a different IBU using BeerTools set to tinseth , then when i use the formula calculated into an excel spread sheet/online calculator

For instance

1.061 Wort, 11 gallons
Simcoe 12.9AA - 60min - 2.00oz

yeilds 38.9 IBUs Using Beer Tools set to Tinseth

The Same addition yeilds 36.71 IBUs in my excell spreadshead, and various online tinseth utilization calculators.

Could BeerTools be using some different constants in the formula or if anybody from the staff knows the exact formula that BeerTools uses I would greatly appreciate some feedback. In the end i am in love with this program. It is without a doubt the best brewing software.
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It doesn't match BTP either

Postby billvelek » Sat Feb 21, 2009 8:21 pm

It doesn't match BTP either. Unless I've messed up the recipe, I just set BTP for an 11 gallon batch of 1.061 O.G. using 2 ounces of Simcoe 12.9%AA LEAF hops (so that I wouldn't need a pellet correction formula) for a one-hour boil using the Tinseth Formulas for both 'Boil Time' and 'Gravity Correction', and the result is 39.3 IBUs. Here is a screen shot: http://home.alltel.net/billvelek/simcoe-1.JPG

If I use just the 'Boil Time' Tinseth formula without the 'Gravity Correction', then my IBUs are 38.3 ... which are still different from your results.

Cheers.

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Postby robert4136 » Sat Feb 21, 2009 9:14 pm

thanks for the reply, i think im on to something, BTP is accounting for different grain bills, for instance a 1.061 wort of all crystal 60 will have a different calculated IBU than a wort of all 2 row, i am assuming the normal online and my excel calculators do not have this calculation built in.

THis is why we are getting different results within BTP itself.
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Why would the grain bill matter?

Postby billvelek » Sat Feb 21, 2009 10:54 pm

Why would the grain bill matter? The only difference it is going to make, as far as I can see, is in the resulting sugar profile within the wort, i.e., the ratios of maltose, maltotriose, fructose, sucrose, glucose, rubinose, dextrose, and any other 'oses' that might be in there. But the gravity is the gravity. I've never heard that one type of sugar versus another will have any effect on hops utilization. You might be right, but it is puzzling to me, because I don't believe there is any chemical reaction between the alpha acids or other hop constituents, ... and sugars. The grain bill will probably have an effect on the proteins that are present, too, but they should precipitate out of the wort as hot break forms, before any hops are added. This is an interesting issue, so I hope that some of our resident brewing experts will jump into this discussion.

Cheers.

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Postby ColoradoBrewer » Sun Feb 22, 2009 8:05 am

Interesting thread. I've been brewing for nine years and accurate bitterness calculations seem to be my final frontier. I just don't have confidence in the bitterness any given brewing software calculates. I suppose that's because there are many different formulas ( at least seven that I know of) and they all calculate a different bitterness for the same batch, and that difference can vary by 20 points or more. So other than analysis by a lab, how's a homebrewer to know the actual bitterness of their beer?

OK, more on topic, in the example Bill posted in his link BTP calculated 39.3 IBU's with a 90 minute boil. I created a recipe using the data from Bill's link and got the same result, 39.3 IBU's. But Robert used a 60 minute boil. Changing boil time to 60 minutes BTP calculated 38.7 IBU's which is very close to what Robert got, but still not the same. Perhaps the difference is merely due to different systems. Glenn Tinseth says as much in the disclaimer on his hop page. BTW, using the calculator on Glenn's page I got 37 IBU's, so go figure. As to why Robert's spreadsheet and BTP differ about all I can think of is there must be a difference in the formulas.

EDIT: The disclaimer is on the bitterness calculator page.
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Utilization

Postby slothrob » Sun Feb 22, 2009 4:24 pm

I've just compared a number of different OGs, grain bills, starting gravities, and boil off rates for a 60 minute hop addition and get virtually identical IBUs with BTP andTinseth's Java Bitterness Calculator. For example: 38.7 vs 39, which are mathematically the same since Tinseth doesn't go to tenths of an IBU. I'm not sure why you are getting different numbers? :?
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Postby billvelek » Sun Feb 22, 2009 4:50 pm

ColoradoBrewer wrote:snip ... in the example Bill posted in his link BTP calculated 39.3 IBU's with a 90 minute boil. ... snip

There was a 90 minute boil only because that's what my template is set for; the _hops_ were only boiled for _60_ minutes, to duplicate the original post. I suppose that the length of boil _might_ have a very _minimal_ effect on the average gravity during the time that the hops are added, but I'm not sure that that is a factor here. In other words, if one brewer has a significantly higher 'boil-off' rate than another brewer, then, in order to end with the same volume and gravity, that brewer would be pitching his hops into a kettle with more wort and a lower gravity at the beginning of the hop boil. Maybe that accounts for the difference; I'd need to know what the original volume at beginning of boil and the boil off rate is in order to make an absolutely accurate comparison.

Cheers.

Bill Velek
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perceived bitterness

Postby robert4136 » Sun Feb 22, 2009 8:09 pm

one quick note before i try to gather some more info .

I kinda have the same grip as bill, the concentration of isohumulone in the wort should be the amount of "IBUs" in the beer, however the International Bitterness Unit is not based on an actual concentration of anything in solution, It is a "perceived" bitterness so which an addition of hops in an all 60L caramel malt would be perceived as less bitterness than the same addition in an all 2-row malt.

with that said, using the tinseth formula on BTP will yield the same amount of IBUs for any wort, its with the wort correction "on" , that the IBUs shift around between different worts. hop this makes sense, don't know exactly how or what the reasoning behind the wort correction is.
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Re: perceived bitterness

Postby slothrob » Sun Feb 22, 2009 10:52 pm

robert4136 wrote:one quick note before i try to gather some more info .

I kinda have the same grip as bill, the concentration of isohumulone in the wort should be the amount of "IBUs" in the beer, however the International Bitterness Unit is not based on an actual concentration of anything in solution, It is a "perceived" bitterness so which an addition of hops in an all 60L caramel malt would be perceived as less bitterness than the same addition in an all 2-row malt.

with that said, using the tinseth formula on BTP will yield the same amount of IBUs for any wort, its with the wort correction "on" , that the IBUs shift around between different worts. hop this makes sense, don't know exactly how or what the reasoning behind the wort correction is.

While IBUs are a mathematically derived estimate, they are an attempt to predict the concentration in ppm of isomerized alpha acids.

The wort concentration correction is due to lower rate of isomerization in more concentrated wort.
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