Re: AHA forum discussion: Is a 90 Min boil needed?

Post #2 made 1 month ago
Is anything "necessary"?
Using the BIAB method typically incorporates both a 90 minute mash and a 90 minute boil. There are graphs that show that additional sugars are indeed extracted from the grist during the thirty minutes after 60 has passed. Diminishing returns are to be determined by the brewer: is 70 minutes enough, or do I go for 90? As for a 90 minute vigorous boil (uncovered), DMS (boiling point = 37 ºC) is not an issue and will not be an issue even using Pilsen malts that are the major cause for alarm. A 90 minute vigorous boil distills off a certain amount of water in my equipment set-up. It results in a Specific Gravity (SpG) that is expertly predicted by the BIABacus. If you choose to boil less vigorously and/or for a shorter time in your equipment, you will get a different VFO and Specific Gravity at the end of your boil. Those differences can be dealt with by approaching the equation with different amounts of grist and different dilution(s) or target SpG. In the extreme case, some may not boil at all. If it works for you and your recipes, congratulations.

As for thiobarbituric acid, give me numbers!
Taste threshold? Oxidation of lipids to produce something else and its impact on taste?
Five is a sufficiently close approximation to infinity. -- Robert Firth "One, two, five." -- Monty Python and the Holy Grail
Break out the GC/MS/MS and find other components to fret about. I am not worried. I just want to make beer. :drink:

Re: AHA forum discussion: Is a 90 Min boil needed?

Post #3 made 1 month ago
I'm also interested in this. Low Oxygen Brewing method also tells you to do a gentle boil for 60 minutes with the kettle semi-covered, lately I'm doing less vigorous boils, but still 90 minutes, will probably try 60 minutes soon. I'm also doing no-chill in the kettle and not using my immersion chiller.

When searching for more on the thiobarbituric acid thing I found another post by Martin here, but there are no references: ... st-8398058

If I find his presentation or any references, I will post them here.
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Re: AHA forum discussion: Is a 90 Min boil needed?

Post #4 made 1 month ago
Page 84 of the pdf linked here: ... ty_of_beer
Finally, the TBA value increased also with the boiling intensity. The lowest applied boiling
intensity resulted in an increase of 14.9 TBA units, while the highest boiling intensity resulted
in an increase of more than 20 TBA units.
In every case, TBA measurement was more
consistent than any volatile available, provided it is used only in brewery applications.
Therefore the best heat load indicator of wort is ∆TBA, which reflects the TBA difference
between the beginning and the end of boiling. The TBA value provides an indication of the
total amount of Maillard intermediates formed and can therefore be regarded as an indicator
of the chemical memory of the wort. Important to note is that the ∆TBA value is not only
dependent on wort composition (e.g. pH, density, amino acid concentration, sugar
composition), but also on boiling intensity, and consequently the boiling system used.
(EDIT: I want to clarify that the above info is for 90 minute boils, the part I quoted doesn't include that information)

Then page 94 has a chart showing an increase between 8 and 9 TBA units for 60 minute boils when PH is between 5 and 5.5 (the usual).

There is much more in that PDF, I just skimmed and searched for "TBA increase", the above stuff seems to be the most relevant.
Last edited by tizoc on 11 Dec 2018, 04:26, edited 1 time in total.
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