Per past experience and discussed before I have seen full attenuation with fast mashes at optima. The time thing starts to become semantics of a point or two at best. I will show my point and also concede to the fact that your point is valid although depending on actual need.
My intention is not to argue about the topic with you in any way, but to maybe further clarify my intended point regarding shorter mash times.
Typically where I am coming from is I have complete conversion and full attenuation that I require with a usual 60 minute simple infusion and this is what I practice and advocate for common ales, although I have seen a proper FG I require if mashing for 30 minutes at 145f and a PH of 5.2 at mash temp. (5.5 PH at room temp)in the past has shown me an OSG of 1.049 and it ferments right down to a FSG of 1.008 with US-o5. So temp and PH along with a mainly base 2 row grain bill became a factor over time in this case and over all my attenuation was 84% Why do I need to or want to go down to 1.006 if the discussion of over 30-60 minutes more is sustained? Then I am to understand this would/should boost fermentability to 86-88% and my FSG lands at 1.005-1.006?, but this was not true as shown by the below example as I hit the full attenuation expected for my grain bill and yeast type used as I expect an apparent attenuation of 81% with us-05.
Here is an example of two exact rye pale ales:
#1 OSG:1.049 FSG 1.008 1 sachet Us-05 84% attenuation, mashed for 30 mins@145f PH: 5.2
#2 OSG:1.049 FSG 1.008 1 sachet us-05 84% attenuation, mashed for 60 minutes@150f PH: 5.3
What exactly did the extra 30 minutes here add to increase the fermentibility or quality of my wort? Also the first running’s were exactly the same SG? Plus the lower temp was the one converted in 30 minutes. It shows that my statement holds water that SG, grain bill and actual need such as yeast type selected become the bigger factors to overall limit of fermentability and if needed then employ an ultra long mash to combat non-typical factors and stretch fementability out to the max if needed.
All of that being said you are still at the same rest temp but for longer to allow the further breakdown of dextrins but still not every chain even at 90+min and at some point you hit the plateau(30-60 minutes IMHO) and sure you boost your SG a few points and and/or ekk out 2-4% attenuation but at the expense of an extra 30 minutes to an hour and then again your yeast may not fully convert every sugar avalible as it hits its own limit of fermentability. What I am trying to convey is that far too many advocate a 90 minute mash and I have shown that I am receiving at/ above 100% conversion of the maltose needed in general uses. Do I need to hit 112-115% by mashing another hour is far over emphasized IMHO. So if you simply have 100+% conversion pull your wort at any time and go.
I feel 30 minutes or less mashing can create over 100% conversion and sugar profile needed as you have hit 100%+ does another hour of mashing create a few extra points sure. But you can make it happen if mash PH and temps are at optima. Again for 98% of the time I advocate a 60 minute mash where you hit 105-110% ----> this 30 minute thing is simply a 2% afterthought should be the main takeaway for newer brewers.
Here is a quote from Kai.
For a given rest time, there will be an optimum at which the most fermentable wort is produced. This optimal temperature depends, among other factors, on the length of the rest time. The shorter the rest, the higher the temperature optimum but also the less fermentable the wort will be
This agrees with my thought about plateau, temp and PH if in optima will need what I have shown is 30 minutes or less, true it also agrees with your statement regarding less ferment-able but it also disagrees with my actual findings of a fully ferment-able wort at anything over 100% conversion which I have found in 30 minutes or less per Kai’s spreadsheet. I think the missing defining factor here is grain bill and SG to be honest.
Now in come cases depending heavily on Grain bill you may need to goto 112-115% in order to chew down from high OSG’s true as you want all/most easily assimilable sugars. But in most common beers I think we can agree it can be done in 30 minutes and be fully converted and attenuation is full at 98% potential maybe. UNLESS you have a special circumstance mash then 90+ minutes may be required to hit 100% possible attenuation is what the difference starts to become.
Here is another quote from Kai that again asserts both points as it tells the viewer that a mash is fully converted at 15 min+. But then adds the fact to validate your point that there is a bit o conversion albeit small and he is stating this by saying conversion efficiency is increased after mash is starch negative. And per my own mashes to mirror 30/60/90 I have shown that your talking the ranges from usually around these numbers per Kai’s spreadsheet used.
a.30minutes = 100% conversion effic per SG readings and starch negative iodine test.
b.60 minutes = 105-110% " "
c.90+ minutes maybe = 112-115% " "
And depending on grain bill and yeast type you may or may not require 115% of sugar converted anyway. If a person is comfortable with 90 minute mash for all that is fine and gravy too, but it really comes down to your own brewday and the set of requirements that exact beer calls for.
"With today’s highly modified and thus enzymatic strong malts, the mash is generally converted after 15-30 min based on the rest temperature. Lower temperatures mashes convert slower than higher temp mashes of the same grist (see The Science of Mashing for further details). Most brewers do however mash 60-90 minutes since the fermentability still increases even after the wort itself is iodine negative. In addition to that longer mash times can also increase the conversion efficiency as they convert the harder to reach starch from the malt. It is always a good practice to check for conversion of the mash with a Starch Test. "
So I will wrap by saying a majority of beer styles can see 30-60 minute mashes and will produce what a brewer needs on an everyday basis with no degradation of quality or taste and very,very minimal degradation of conversion,attenuation if any depending on factors.
