Where Does the Protein Go?

So I've brewed 2X now using a kit, like alot of people have probably started out with. However recently I've become interested in brewing on a more custom level. Despite my research I'm not fully understanding something. I've been stumped what happens to the high protein content of barley during the brewing process. Obviously the germination process is stopped when the enzymes are produced but why is it that beer generally ends up with such a drastically lower protein content? I know Proteins must be present for head retention and the fermentation process doesn't seem to involve consuming the polypeptides but clearly I'm not seeing the full picture. I was hoping someone could explain what happens to the proteins originally stored in the grain and most importantly, if there was anyway to retain alot of that protein content in the final product?

All that hot break and cold break material...that is where the bulk of your proteins get tied up, you would not want to retain that in beer. A little going to the fermenter is good for yeast health; but, too much is associated with off flavors...some folks don't care enough and dump it into the fermenter, others, such as myself whirlpool and let it settle out and send a clear wort to the fermenter. Obviously what you see is not soluble so it gets tossed. I suppose you could dry it up some and eat it or turn it into animal feed...I'd venture a guess larger breweries do just that.

hmm, thanks. So basically the amount of protein that's soluble is very low?

Much of the protein that is in the grain itself is in the germ and the polycarp layer of the barley kernel. The germ obviously gets left behind in the mash/lauter tun in it's solid form so that doesn't make it into the wort. The Alerone layer contains 30% of the barley kernel's proteins and releases some of those as our amylase enzymes during malting (so some of the protein content is tied up in enzymes) but some of it gets left behind in the husk. -This is why higher enzymatic power malts have higher protein contents and vice versa; much of the protein content IS enzymes.

The alerone layer is also releasing proteases during the malting process which are breaking down high molecular weight proteins into medium weight proteins (the ones that aid head formation / retention) and then further break down those medium weight proteins into amino acids and free amino nitrogen which is our natural yeast nutrient.

Well modified malts like pale ale malts and munich malt have these proteins broken down further and more of the proteases denatured than less modified lager malts which have more and higher weight proteins but also more enzymatic power / proteases available (see why a protein rest is recommended on these?).

As Bensiff stated the nonsoluable proteins come out of solution / form complexes via hot and cold break (and they're even less soluable at lower ph) so they get left behind.


I'm not sure why you think that more protein is a good thing; high protein levels are certainly responsible for chill haze and general product instability. The high molecular weight proteins are the ones that combine with polyphenols to form chill haze, the medium weight proteins are the head forming proteins and the little amino acids are our yeast nutrients.

Even very well modified malts have plenty of protein in the form of enzymatic power, have enough protein to provide a good head, and provide enough amino acids for yeast nutrition so focusing on increasing finished protein levels will probably decrease your beer quality over all; not increase it.



Adam

Bensiff said:

... (I) whirlpool and let it settle out and send a clear wort to the fermenter...

Click to expand...

How do you whirlpool? What is the technique?

With the wort chiller and the braided tubing in the kettle, and a plastic mash paddle, I wonder how you get a good whirlpool going?

Biertourist, really appreciate such an in-depth answer. As for why I would think more protein would be a good thing for a better beer, that's not necessarily the case. For my own purposes I was curious if you could retain the nutrition of the pre-malted barley. The affects to taste/haze/etc non-withstanding I thought it'd be interesting project to brew a beer with a high protein content (and discover the consequences), and upon looking into it lead to the original question of where it all went. Adding some nutritional protein content to my brew seems like something the hasn't really been done.
Now that the original issue is cleared up I guess before I abandon the idea I'm wondering if say adding an amount of heat-stable whey protein to the wort would be a viable alternative, or if you had any other recommendations that you think would steer me in the right direction.