I had a couple people write in with the same question. I asked Gordon Strong (Zymurgy’s technical editor) to take a look, and I’m sharing his response here:
“That’s what was in their original recipe. Seemed short to me; my system would need at least 30 minutes at that temperature, but conversion speeds vary. I’m guessing the difference is that on professional systems, they likely achieve a much more complete grind of the grain so that the starches convert quickly. On the average homebrew system, that duration is likely too aggressive. I would extend the 154F rest to 45 minutes to be safe. The 122F rest is a protein rest; 10 minutes is fine. The mash out temp (170F) is fine. The 154F rest is the last saccharification rest, so brewers should always interpret a recipe to include the phrase “or until conversion is complete” on the last rest. That’s similar to a food recipe saying “cook until done” after giving a time estimate. An iodine test can confirm, but most mashes will fully convert in 30-60 minutes at the homebrew level. So, that’s a good catch, and shows a difference between what can be accomplished on a professional system vs. the average homebrew system.”
Hope that helps! (And sorry I’m late to the game on this; just got back from vacation).
also, I wonder how long it takes them to raise temps to mash out? If if is a long process they would stay in the conversion temperature range for longer then 15 minutes during the rise…
It also takes considerable time to mash in, and the pros often are mixing the grist and water as they go in, so conversion will be taking place on a portion as the mash in progresses.