Hot side oxidation and beer taste

[lupulus]

Chatting yesterday with good friend @mchrispen, I mentioned that I am preparing a presentation on the Literature of hot side aeration / oxidation. He asked me whether I was going to discuss enzymatic (aka enzymic) browning. I told him No, because I was not able to find literature about how that would affect the final beer; he said he would send me some papers on it, which brings me to the point of the topic.

Can you please point out to any reference (that you know of) that links hot side oxidation (or any process within it) and final beer taste?

Thanks in advance,

[Weizenberg]

If you look in Die Bierbrauerei: Vol 2, 8th extended edition, there is information dotted all over. The way I understand it, is that the information you are looking for is embedded in the discussion about the senory impact of various mash schedules. This precludes a good understanding of the basic influencing factors though. On page 660 par 8.1.2 you may find an intersting discussion about other factors relating to the effects of oxygen ingress into wort.

All this begs the question, what are the objective parameters to evaluate and measure the oxidative effect on mash? If you can provide some pointers then I'd happily take an occasional dig into the literature and attempt to tranlsate it for you.

Gut Sud!

[lupulus]

Thanks so much.
I will try to get a copy. I have the summary (Abriss) but I reckon it is not there...

ref your question, in Abriss, Narziss mentions that the best way to measure mash oxidation is by sulfite consumption.

Going back to what I would like to collect, it is as much data as possible on experiments that modified mash conditions and measured "taste" (organoleptic I mean)

There are just a few papers that measured taste, using the DLG test and the Eichhorn aging test. The DLG is not perfect either and has been challenged (Wurzbacher dissertation for example) but there is not much out there so I take what I can get...

Thanks again !!

[Weizenberg]

There are loads of useful tables that often number the quality of the sensory perception. I always wondered what the criteria were, because they seemed rather subjective to me.

I would be interested to hear of your findings, if you don't mind. In the meantime I'll keep a lookout for you and shall post here of any more relevant material i come across.

[Techbrau]

In my searching I haven't found very many published academic papers that take a holistic enough view to explicitly make the link between enzymatic oxidation of phenolics and flavor in the context of beer. However if you look at wine literature or even just food science in general it is widely known that low molecular weight phenolics are very flavor active and play a role in the perceived "freshness" of fruits and vegetables.

Just do a google search using keywords like "polyphenol oxidase" and "flavor loss" and you will get literally thousands of results that study its role in the staling of everything from apples to potatoes to grapes to peppers.

Like Nico said both Kunze and Narziss claim improved flavor and "freshness" by inhibiting the action of polyphenol oxidase, peroxidase, and lipoxygenase during processing many times throughout their textbooks. It's widely known that malt contains these classes of enzymes and is also rich in phenolics in general (just google search "polyphenol oxidase beer" for example), but like I said not enough academic papers study the end-to-end nature of the problem, and instead concern themselves with much more limited experiments, such as measuring polyphenol concentration under different conditions. Even that can be misleading depending on which compounds are accounted for, since oxidation can actually increase the amount of high molecular weight polyphenols present via polymerization of individual phenolics. So don't look to polyphenol concentration alone to be indicative at all of oxidation damage.

[lupulus]

Thanks for the advice @Techbrau !
I have not thought of it from that perspective, so I will be doing some reading.

@Nico - To your request to share what I have found...

The best review and the basis for my presentation is the (free) article by Meilgaard.
http://onlinelibrary.wiley.com/doi/10.1 ... 098.x/epdf
Meilgaard conclusions are mirrored by Bamforth in his Flavor stability chapter of Beer, a quality perspective.
A very interesting and amusing point by Meilgaard is the one in the next to last paragraph in pp.274 "Altogether the evidence for any positive flavour effects of oxygen exclusion is limited. Studies showing damage from oxygen were all performed on a lab scale and little effect is shown on an industrial scale."
This is the opposite of what the "homebrew gurus" have always said... "HSA may exist on an industrial scale, but it is a myth at the homebrew level"
My personal bias at the moment is that there is a difference in some styles, but it is not big and will not make a bad brewer into a great brewer. I will keep my bias to myself until I have more data though

If you find something on this area, please send it my way.

cheers,

[Techbrau]

[lupulus]

Thanks Tech
I tried the yeast method twice and went back to deareation by boiling. Does not take much effort for me.
I also put the Sauergut 30 min before mash-in.

The AA combined with BrewtanB and half/half SMB and PMB is working well for me. I had flavor issues with some yeasts last year, and this year is going well. No flavor issues.
Boiloff is about 8.3%/h I try to get start with 28L and end with 24.5L after 90 min.
In my experience, you start getting coagulation problems if you go much lower than 8% (Ireks-Avangard will have big clarity issues with simmer boils).
All my worts are clear going into the fermenter.
I have not tried 6% / h - I am scared honestly. Most likely the boiling convection does depend on the type of heating and even shape of the heating element, and one time last year when I did about 6% by mistake got some haze in the wort going into the fermenter despite hot and cold crash.

How much sauergut are you using for the mash and for the EO boil?

[Techbrau]

[Weizenberg]