A single rest at 153F will span both alpha and beta ranges and will be sufficient for 95+% of your brewing. That said, the best way to know what a particular rest will do is to try it for yourself. It's not going to ruin a beer.
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I have to disagree here. β will be largely inactive at 153 °F. If you are going to choose a single infusion rest temperature, I'd say you are better served choosing a lower temperature.
In the end, single infusion mashing is a very useful compromise, especially given the fact that some people cannot direct fire step mash. Set aside esoteric flavor discussions and the "better or worse" argument between step mashing and single infusion. The true beauty of the step mash is how it gives complete control of the wort composition to the brewer.
One of the greatest overviews I have seen came from an article of Brauwelt that detailed a multi step mash. It talked about ideal β rest temperatures and times, particularly the half life of β amylase at those temperatures:
144 °F (20 minutes gives ~ 46% of β amylase activity)
147 °F for (10 minutes gives ~25% additional of β amylase activity while 10 more minutes here gives ~10% additional β amylase activity)
153 °F (20 minutes. By the time you enter this rest there is no residual β amylase activity, although the ramp from 147 °F to 153 °F will likely net an additional 5% β amylase activity)
162 °F (30 minute α amylase rest. This promotes full body)
171 °F (10 minute mashout promotes glycoproteins and other foam positive substances)
A nice compromise would be 144 °F for 18-20 minutes, 147 °F for 8-10 minutes, Step through 153 °F on the way to 162 °F where you rest for 30 minutes then mashout for 10 minutes at 171 °F.
For a single infusion, a temperature between 147-150 °F may be ideal.
IIRC both Greg Doss (when he was at Wyeast) and Kai both reported maximum fermentabily for single infusion mashes at 153F using Pils Malt. That is what I remember, haven't looked at those in some time. Greg presented at an NHC, so you might find that on the NHC page.
Your thoughts? I have have had good results on certain beers using a single at 153F. US 2-row is so "hot" in DP that big breweries say the mash is pretty much converted when they are done mashing in 200 bbls. For some malts I see where a step mash is they way to go, for US malts, not so much.
I'd be curious to know the mash time that G. Doss and Kai recommend for that temperature. You have to think about it along the lines of the Single Infusion being a compromise between the various elements of mash chemistry. That doesn't mean it's bad it just means that there is an inherent compromise when the amylase enzymes each have their own desired pH ranges and temperature ranges.
I can see 5 step mash like the one outlined in the Brauwelt article as semi-equivalent to a single infusion mash at a higher temperature when mashed for longer. If you truncate the various beta amylase rests in the previously posted diagram down to the half-life values of beta amylase at those temperatures, and assume a 1 C/min ramp between steps, you'd get the following:
144 F (20 min rest)
147 F (2 min ramp, 10 min rest)
153 F (3 min ramp, 5 min rest)
162 F (5 min ramp, 30 min rest)
171 F (5 min ramp, 10 min rest)
for a total of 90 minutes, including ramp times. Now if by mashing a single temperature in a "tweener" range for beta and alpha amylase, and extending the rest to 90 minutes, you get a similar fermentability from your wort, than that works out great. You lose a bit of control but in the end single infusion offers a compromise for those who may not have the means to step mash, or an SOP for those who can and just prefer not to.
Either way, it tends to be the same amount of time.