BeerSmith™ Home Brewing Forum

Brewing Topics => Introductions => Topic started by: SEWallace on November 28, 2019, 11:37:52 AM

Title: Noober Brewer....
Post by: SEWallace on November 28, 2019, 11:37:52 AM
Hey All..  been lurking for a while..  but since I've started using BeerSmith (beats the heck out of my excel sheet!) I am trying t understand the brewing process a little more...

One item that has me a bit confused..   I have 'transcribed' some Brewers best recipes into my library (ones that I have made.. and may want to modify..) but the IBUs (from the recipe) never match the IBUs that BeerSmith calculates...   

Is that something to be expected.. or am I (some how) using BeerSmith wrong
Title: Re: Noober Brewer....
Post by: Oginme on November 28, 2019, 12:51:29 PM

There are a number of things that will cause a difference in IBU between a recipe which is printed and how the calculations come out in the software. 

First, there are a number of different models for the estimation of IBU.  If you are using BeerSmith as it came the default IBU model is Tinseth.  The software also gives you the options of using Garetz or Rager.  Each of these will give you different values.  I am not sure what calculation the Brewer's Best kits use for their published IBU, so that may be one significant difference.

Next, hops are an agricultural product and the amount of the bittering components can (and do) change from year to year, lot to lot, grower to grower, field to field, beginning of picking period to end of picking period.  Even within a lot of hops, the % alpha acids can vary greatly.  The %AA for your particular lot of hops may vary from the standard used in the recipe calculations made by Brewers Best. Since they are producing and boxing a number of kits at one time and not necessarily using the same hop lot or bale to package from, they most likely use a typical average for the hops they use for a particular recipe.

Third, your process has its own peculiarities in terms of losses and efficiency.  If your process has significant losses (or no losses) post boil, this can affect the amount of IBU which make it through the system into the fermenter.   

Lastly, the issue I have with IBU is that it is the estimation of tested value which has a rough correlation with the perception of bitterness.  The test also does not include other components which contribute to bitterness perception in beer, so in its own use it is an imperfect measure of bitterness.  Unfortunately, it is the only metric we have to estimate the bittering perception in a beer.  Even then, it is difficult for most brewers to distinguish between two beers that are less than 5 (some say greater than that) IBU difference (as tested).

My advice is to not worry too much about trying to get the kit to match what the software states in terms of bitterness.  Brew the kit, taste the beer, enjoy! 

Title: Re: Noober Brewer....
Post by: SEWallace on November 29, 2019, 07:11:02 AM
I have adjusted the %AA for the actual hops shipped....  but it still way off (double..)

I'll have to check those options for IBU model..    see if any approach the BB estimation.

Thanks for the thorough response...

Title: Re: Noober Brewer....
Post by: Oginme on November 29, 2019, 09:07:43 AM
If you want another set of eyes looking at it, export the recipe as a .bsmx file and post it here.  You can export the file by highlighting the recipe in the folder and then clicking on 'file' > 'export selected'.  Then follow the prompts to save the file onto your computer.