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I have been looking at brewing several recipes that call for a multi-step mash that includes a protein rest. I saw a Mr Wizard article in BYO that sort of defends protein rests.

Just like the questioner in that article, I thought that protein rests were unnecessary for well-modified malts, but Mr Wizard says that brewers still consider a protein rest necessary where there is 20% of more wheat in the grain bill (for clarity purposes, I guess), or to ease separate of wort in the lauter.

This doesn't make sense to me, because it seems that any proteolytic enzymes in the malted wheat (and other malts) would have been destroyed by the malting process, meaning that no protein is being affected by the protein rest. Is it correct that there are no or negligible amounts of proteolytic enzymes in modern malted grains?

Also, as far as separating wort, wouldn't a mash-out step or high-temp sparge do the same, if you bring the mash up to 170°F?

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2 Answers

up vote 5 down vote accepted

First, keep in mind that Mr. wizard is a commercial brewer and his answers come from that point of view. It may not be applicable to homebrewers.

Using wheat may be about the only case where using a protein rest may be of benefit. But it'a not a given. There are still proteolytic enzymes left in the malt. Due to the high protein content of wheat, it can possibly lead t stuck runoffs and a p rest may help that. Notice that there's a lot of "maybe" in my statements. That's because it's not a cut and dried situation. Here's an excerpt from my upcoming book "Experimental Brewing" that may help explain it....

It turns out that wheat doesn’t have significantly higher protein levels compared to barley, but due to solubility factors, it leeches more protein into the wort. Here’s the funny part about our traditional wisdom – according to a recent study from Leuven, Belgium – wheat provides some better foam stability characteristics, but only for brews with highly modified malts and only in the higher gravity versions and only when gassed with Nitrogen instead of CO2. Even better – we know that Wheat is supposed to induced hazy cloudy beers, right? The effect of wheat protein haze is more pronounced at lower overall levels of wheat in the mash – i.e. a beer brewed with 20% wheat will be hazier than a beer brewed with 40% wheat. According to the researchers this is believed to be due to the more aggressive breakdown of the large protein strands in the 20% wheat beer. This leads to smaller particles that are less likely to settle out.

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During malting, the maltster uses the kiln to dry out the malts. Pilsner, wheat and other light malts are heated to 45°C with a lot of ventilation. This dries out the malt considerably. Once the moisture content has been sufficiently reduced, the temperature can be increased to higher temperatures - the low moisture content protects the enzymes to some degree, although for more strongly kilned malts, the enzymes still denature due to the high temperatures and longer time.

So, the enzymes are still present, and a protein rest is still useful for altering the profile of different length proteins in the wort.

see

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