You’ve all heard of it, maybe even spent the time doing it. The infamous decoction. With certain historical significance, the decoction mash remains either a holy grail of brewing or a serious waste of time. But, what is the deal with decoction? Should we entertain the idea of brewing that amazing lager after slaving for twelve hours over the brew kettle? Or should we just leave this technique for the history books?
Before we dive into the discussion, let’s take a moment to define a decoction mash. As a technique, the decoction mash is a multi-step mash schedule where the brewer removes a portion of the mash, raises the temperature and boils this portion, then adds the portion back to the mash to raise the temperature of the entire mash. This, historically, was repeated three times giving what we know as a triple decoction (single and double decoctions also exist). Common temperature steps during a triple decoction are mash in at mid to upper 30s (acid rest), raise to lower 50s (protein rest), raise to mid 60s (regular saccrification rest) and a final raise to upper 70s (mash out). Traditionally, a triple decoction mash took about 4 hours to complete, and is still a technique used by some breweries today.
Malt. A real reason for conducting a decoction mash was because malt used to be quite unmodified. To control pH, break down proteins and increase extraction, brewers needed to run a multi-step mash schedule. Malt of today is very well modified and does not need to be handled in the same way. In fact, it could be detrimental to the final beer to run well modified malt through a serious of temperature steps. A common worry with decoction mashing is that the enzymes of the boiled portions of the mash are denatured. While true, the majority of enzymes actually dissolve into the main mash liquid. The boiled portion of the mash contains a small percentage of the total enzymes and, therefore, will not make an enzyme deficient mash. It is actually common to experience a 5% rise in efficiency with a decoction. This could be a welcome helping hand for us struggling homebrewers and would certainly be a plus for a professional brewery. But, malt is one of the cheaper ingredients. Adding 10% more weight to your grain bill will help you hit the numbers without having to go through the lengthy decoction process.
Flavor. Many people claim that the decoction process gives the beer a more distinguished malt flavor, a flavor you cannot get from a single infusion mash. While melanoidin production is increased with a decoction mash, similar flavors may be achieved by adding additional melanoidin or munich type malts to the recipe. The amount of melanoidins produced during a decoction mash is very dependent on how aggressively the decoctions are boiled as well as protein levels in the malt. You may not get that classic decoction flavor because of your brewing technique. Tannin extraction is also a big concern for many. We learn to never raise the temperature of the mash above 77°C for fear of extracting unwanted tannins. The difference with a decoction is that the small boiled portions have a lower pH than the main mash. This lower pH coupled with a higher temperature actually limit the amount of tannins that are extracted. Any extracted tannins are actually a flavor positive aspect of decocted beers. Lastly, decoction mashes have actually been known to decrease DMS levels in otherwise DMS heavy lager styles. This is due to less breakdown of proteins during the boiling of the removed portion of the mash.
For the fun. As a homebrewer, the novelty of conducting a decoction mash is a draw. Think about serving up a cold glass of perfect lager, triple decoction lager, to your friends. This would be both fun and fulfilling. The decoction process, however, is very time consuming and uses a lot of energy. Historically speaking, a decoction mash is suitable for only a handful of classic German styles. Is it worth the time and effort to produce a handful of less popular styles? Or is it a must do technique to produce historically delicious styles? This decision, of course, falls in the hands of brewer.
So the questions remain. Is a decoction mash worth the effort when we can brew just as good, maybe better beers in less time? Or is a decoction the reason why those classic German styles stick out and taste differently?