Beerlust Posted October 30, 2013 Share Posted October 30, 2013 Hi guys. Just following on from the discussion in the Big American IPA (Advice Needed) thread, I was wondering when a commercial brewer (or home brewer for that matter) states an IBU number for their beer, is that number relative to what the consumer tastes at the glass, or is that number assigned before primary fermentation begins? [unsure] Even before I began brewing, I'd always assumed that number was relevant to what you tasted out of the glass. [innocent] If indeed IBU numbers are based on levels attained pre-fermentation, & given how certain yeasts impact on hop characteristics, these quoted IBU numbers could be quite deceiving by the time it is poured into the glass & tasted. [ninja] Cheers, Anthony. Link to comment Share on other sites More sharing options...
Hairy Posted October 30, 2013 Share Posted October 30, 2013 I would assume your homebrew calculation is pre-fermentation. You will need to measure it scientifically to determine the IBUs in the glass. This article may help: Behind the IBU: Advanced Brewing In the homebrew environment we are just estimating anyway. There are lots of variables that affect the calculation of IBUs. You use the alpha acid percentage on the packet; is this correct? You store the hops for a period in the freezer or fridge; how much has the AA% now changed? How vigorous was the boil? What was the gravity of the boil? The gravity changes as you boil off. In the end you get close for what you need it for. A ballpark feel for how bitter it will be. Link to comment Share on other sites More sharing options...
Beerlust Posted October 30, 2013 Author Share Posted October 30, 2013 Thanks for the link to John Palmer's article Hairy. The article was filled with a lot of scientific jargon early on (way over my head), but interesting none the less. By the end of the article much of how IBU calculations come to be, had been put into a more understandable perspective for a home brewer. However' date=' the \u201csimple\u201d method of IBU calculation based on the alpha acid content of our hops, boil time and wort gravity works well in practice and should yield a value in the ballpark of the IBU value that would be measured by the spectrophotometric method. We don\u2019t need to develop a perfect model. We simply need to understand the basis of an IBU, and what it means as a target for our raw materials. We can then apply our skill and art as brewers to craft a good beer.[/quote'] That statement is good enough for me. [joyful] Thanks, Anthony. Link to comment Share on other sites More sharing options...
Lotm Posted October 31, 2013 Share Posted October 31, 2013 IBUs is just a number, I reckon it's all about perceived bitterness. I've had 100 IBU beers that I perceived less bitter than beers with less IBUs. Malt profile, yeast, volatile oils, and taster palette all affect perceived bitterness. I just love beer. Link to comment Share on other sites More sharing options...
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