Raw ale, also known as "no-boil" or "no boil" beer, is beer that is produced from wort that either does not reach boiling temperatures or reaches boiling temperatures only for a short time such that the flavor influence from a traditional boil is minimal during the brewing process . This process was typical historically for styles such as Berliner Weisse and farmhouse ales.
Lars Marius Garshol researched historical farmhouse brewing as well as modern-day brewers in the Scandinavian and Baltic regions who preserve at least some aspects of historical brewing techniques where raw ale is still brewed today. Garshol defines "raw ale" as follows:
"Strange as it might sound, raw ale is a fuzzy concept, because there's no sharp line dividing raw ale from boiled ale. Sometimes people boil only 1/6th of the wort. Is it then raw ale? Normal beer is boiled for at least an hour, but farmhouse ale can be boiled for 2 minutes. Is it then really boiled ale?
For the drinker, what matters the most is the flavour, so I tend to use the yardstick that if the process makes it taste like boiled beer I'll consider it boiled beer. Thus, if most of the wort is raw, or the boil is so short that the hops don't isomerize and there's no hot break releasing the protein then it's a raw ale. Unfortunately, I have no emperical evidence for where the dividing line lies, so for now let's say a boil shorter than 30 minutes gives you a technically raw ale.
Having said that, the majority of people making raw ale don't boil at all. In fact, a number of farmhouse brewers consider that boiling the wort will spoil the beer ."
Impact on Brewing
Generally, the lack of boiling has several impacts on the brewing process. Boiling wort serves several functions:
- Evaporation water that condenses the malt sugars.
- Volatiles such as dimethyl sulfide (DMS) and potentially some nutrients that are collected from the mash are driven off or destroyed. In regards to DMS, this surprisingly appears not to be a problem with many raw ales (see the Dimethyl Sulfide page for possible explanations for this).
- Alpha acids contained in hops are isomerized into iso-alpha acids, which makes them soluble in the wort and contributes beer's classic bitter flavor component.
- Boiling also serves to pasteurize the beer since mashing temperatures are not hot enough to pasteurize wort (see the kettle souring page for details and references).
- During the beginning of boiling the wort, a hot break occurs which coagulates proteins and helps them to settle at the bottom of the kettle. These proteins are thought to contribute to staling if they make it through the brewing process and into the packaged product.
- Maillard reactions may occur during boiling which could potentially darken the wort and/or impact the flavor .
- Enzymes that break down various starches, sugars, proteins, etc. are denatured at boiling temperatures.
For more information on the chemical reactions of boiling, see:
Each of these factors plays a combined role in how boiling wort contributes to the flavor and stability of the final beer. Raw ale, depending on how it is boiled, will lack some or all of these effects of boiling. Some of the effects of boiling which are achieved early on may still be retained by raw ale; for example, if raw ale is brought to near boiling temperatures, then it should be pasteurized. In another example, hops continue to isomerize below boiling temperatures, but at a much slower rate (see boiling hops), so some bitterness can still be achieved.