Crystal Malt and Oxidation

[BeerAndTele]

Hello all. I was listening to an interesting interview on The Craft Beer Channel, talking to Vinny Cilurzo from Russian River about brewing west coast IPAs. He mentions that they have removed caramel/crystal malts from their IPAs - and replaced them with Munich malt - because "crystal malt aids in oxidation." He goes on to say, "the roasting process is creating some negative attributes in the crystal malt which aids in oxidation."

I did a quick Google search and found a 2018 article in Craft Beer & Brewing magazine which reads, "Now, hard science on this is hard to come by, but there’s a growing impression among brewers that significant use of crystal and caramel malts can accelerate oxidation and rapidly erode hops character in beers, under certain circumstances. This, as noted above, is ironic, since caramel and crystal malts usually develop as part of their production an increased melanoidin level—and melanoidins are powerful antioxidants."

So my question is, what is going on scientifically that would "create negative attributes which aid in oxidation" ... and why would other kilned malts such as Munich 20L or 30L not have the same attributes?

Here's a link to the interview, with the crystal malt bit at around the 16:00 mark.

 

[VikeMan]

I did a quick Google search and found a 2018 article in Craft Beer & Brewing magazine which reads, "Now, hard science on this is hard to come by, but there’s a growing impression among brewers that significant use of crystal and caramel malts can accelerate oxidation and rapidly erode hops character in beers, under certain circumstances. This, as noted above, is ironic, since caramel and crystal malts usually develop as part of their production an increased melanoidin level—and melanoidins are powerful antioxidants."

One potential issue is this... Melanoidins can themselves become oxidized. If this happens before fermentation, the oxidized melanoidins can in turn oxidize fusel alcohols during fermentation (before the yeast has converted the fusels to esters), turning the fusels into aldehydes.

... and why would other kilned malts such as Munich 20L or 30L not have the same attributes?

Beats me.

 

[Silver_Is_Money]

I realize that this (my response) does not speak directly to the matter of Caramel/Crystal malts, but it's much easier to switch to a LOX free base malt whereby to nigh on eliminate ~75-80% of oxidation potential within a common grist than it is to chase your tail over why your beer is oxidizing.

And hopefully, once LOX Free base malts become more popular varietals, the big box maltsters will begin kilning them into other of the various malt classes, including Caramel/Crystal.

 

[tracer bullet]

Crystal malts have different processing compared to Munich or other malts. I suspect that's the reason they are considered special this way, unlike the rest. Look up how they're made if you aren't familiar with it - partly as it pertains to this but partly because it's pretty cool.

anyhow, I thought I heard a podcast some time ago saying the Maillard reaction had something to do with it. Unfortunately that is all I can remember (if I even do remember that much correctly). And I'm not calling it a fact!

 

[thehaze]

I wouldn't go ahead and say that crystal/caramel malts aid in oxidation, although there could easily be truth to this statement. Some crystal/caramel malts can add some aroma and flavour, that can be identified as oxidation - this is one of the reasons I haven't been using them in IPAs and anything pale/hoppy, for years ( and also because hop expression is cleaner when the base malts are clean - crystal malts can easily become way too noticeable in hoppy beers, especially with time, and it does not even have to be a long time ).

I still use crystal malts in styles where they can befit the aroma/flavour profile. Higher kilned " base " malts do not forego the same malting/roasting process as crystal malts. I regularly use Simpsons Imperial, which quickly became a favourite for different styles, and have not noticed any negative impact on the final beer. I use Barke Vienna and Barke Munich, and sometimes Munich II from Weyermann and can't say I've tasted anything close to oxidation in the final beer. However, when brewing beer, oxidation can be caused by many things, crystal malt being just one variable. As the interview is with Russian River and they are known for their IPAs, I would say that if you wish to implement something in your way of brewing IPAs, it would be to drop crystal malts and only use base malts: Pilsner, Pale malts, Vienna, Golden Promise, Halcyon, Maris Otter ( in lower %, just as with Vienna malts ), etc. and / or a combination of these. Your taste buds will thank you. Cheers!

 

[troxerX]

Very limited research online but found a couple pointers, one of them confirming @VikeMan aldehyde’s point.

https://pubs.acs.org/doi/pdf/10.1021/jf300749r
https://www.sciencedirect.com/science/article/abs/pii/S0733521022000534

 

[MaxStout]

I'm seeing bits and pieces of information re crystal malts and oxidation. There is a brief mention in John Mallett's Malt, of C60 being "prone to oxidation within a very short period of time" (p25). But the book doesn't present what factors cause this, though I'm betting it's Maillard compounds, as cited in the papers linked by @troxerX. Perhaps the different process of making crystal malts--stewing before kilning.

 

[troxerX]

@MaxStout I’m now wondering if it’s based on Maillard reactions if mash decoctions will also be impacted by this misfortune..

 

[MaxStout]

@MaxStout I’m now wondering if it’s based on Maillard reactions if mash decoctions will also be impacted by this misfortune..

Hmmm...interesting thought. Sounds theoretically possible. Does decoction produce the same kinds of Maillard byproducts that are susceptible to oxidation? Someone who knows more about decoctions needs to jump in here, as I've never done one.

 

[Red over White]

In Chapter 4 of Principles of Brewing Science some of this conversation is covered with references to studies. It's a dated book, but has some information for perhaps a jumping off point. Some cold side issues seem to be started in the malt house and others in wort production.