Thinking about mashing
Leah and I brew a lot of lagers (our first major investment, long before going all-grain, was a chest freezer and external thermostat) so my buddy Michael, who heads up our homebrew club's competition team, asked me to talk to the team about lagering. Now, we've made a lot of tasty lagers--including two that have won awards--but I'm not an expert. In fact, our lagering process has evolved over time so I don't really even have a specific method to champion. So I decided to turn to a book I read a long time ago; a quite technical book that I didn't even really understand when I first read it: Greg Noonan's New Brewing Lager Beer.
Re-reading it really got me thinking about mashing... To me, the primary reason to brew lagers is to let the malt shine. After all, if you're just going to make a hop bomb why go through all the effort of lagering? I think most ale brewers don't give much thought to mashing other than the temperature of their infusion because it's just not as important as the hop schedule or the yeast used. But if you're brewing a nice, clean lager, the depth of your malt character is the difference between a so-so beer and an incredible one.
Now I've occasionally employed protein rests and decoctions, but honestly I never really thought that much about them. I just knew that they're traditional, and some people swear by them while others think they're pointless with modern, modified malts. The specific mash schedules I've followed (usually either decocting from protein rest to saccharification rest or decocting from sacc rest to mash-out) were chosen because 1.) somebody said it worked for them and 2.) it wasn't too labor-intensive. But lately I've defaulted to simple infusion mashes because most American breweries do them and I figure if it's good enough for them, it's good enough for me. Is it though?
Re-reading Noonan reminded me of one fact: a single saccharification rest around 152°F is a compromise. So is a rest at 148°F or 156°F for that matter. Beta amylase, which breaks down starches to highly-fermentable maltose, works best between 131 and 150°F. Alpha amylase, which also converts starches to maltose but creates unfermentable dextrins (more complex sugars that make malty beers taste malty) in the process, works best between 154 and 162°F. Notice how those two don't overlap? Yeah, when you do a single infusion mash at 153°F (something I do all the time) neither enzyme is in its happy zone.
Anyway, lots of people think the only advantage of a decoction is the boiling, which causes Maillard reactions. However, when you decoct, you step mash, and when you step mash, you're resting at different temperatures and getting more out of your enzymes. And when you decoct, you're taking parts of your rest through various temperatures repeatedly, thereby going through optimal temps for various enzymes at least twice. The end result, according to some, is a fuller maltiness. Maybe you could draw an analogy to adding hops throughout the boil rather than at once?
Now, there are traditional double and triple decoctions, with a double doing protein and sacc rests and a triple doing an acid rest in addition to protein and sacc rests. However, in each of those they still employ one sacc rest that strikes a balance between beta amylase and alpha amylase. However, both Noonan and David Miller mention an alternative double decoction with rests at 131°F and 158°F. The first rest acts as both a protein rest AND a beta amylase rest while the latter is optimal for alpha amylase. In fact, Miller recommends such a schedule--stepping with a hot water infusion rather than a decoction--for Pilsners. Seems like a logical way to go to me.
Tomorrow we'll be brewing our Christmas beer, which once again will be a Vanilla Doppelsticke. I'm thinking of going with a 131°F/158°F step mash. This winter I'm thinking of brewing a Munich Dunkel with 100% Munich malt and doing a double decoction just to see what kind of malt character I can get out of it. Who knows... maybe I'll find it's not worth the trouble. But you never know until you try!