The science behind beer degradation

can you maybe post some pics of beers you've bought/consumed/seen on shelves recently with the best-by/bottled-on dates for reference?

 

Here's a start - do some more Googlin' of "Dalgliesh" with various other terms added... Not sure if I ever found the original 1977 report (see footnote).

Note that the (US) Brewers Association has an image of the above graph titled "Schema of beer aging/flavor changes" with "months" added along the X axis (months 1- 6) which might turn up in Google Image searches - not sure if Dalgliesh would agree.

So, they consider that their beers are "fine" for 12 months, but the brewers are good with adding 6 month additional shelf life so buyers can purchase "less than fine" beer?

Lots of US brewers in the post-Repeal/pre-Craft era had pull-dates based on shelf life lengths of 2 - 4 months See BEER FRESHNESS AND DATE CODING

 

I honestly would like to see, say, a Malzmuhle Koelsch bottle with dating bc I failed to pay attention to that when I was over there and missed it.

As to darker beers having a longer shelf life, id tend to generally agree as the roasted (or in the case of a beer we brew, smoked) malts can have anti-oxidative properties.

this is another reason id like to see a variety of beers that you mention. some are more subject to quicker degradation than others for a number of reasons: vessel; style/malt used; hop and other desired aromas; the equipment and processes used (low DO brewing methods, filtration, pasteurization, etc).

 

Well, I posted the graph not so much as an "answer" to your question but because "C.E. Dalgliesh" (best known for the illustration, unfortunately, rather than the paper where it originated) is a good starting point for your research into the subject. Lots of the work in the +40 years after Dalgliesh cite or were continuations of his original work.

For "Ribes" see The development of ribes flavour in beer is closely correlated with headspace air.

"Blackcurrent" is the common answer - which, for many (including me) isn't much help at all... Seen it referred to as synonymous to "catty", too (although I've also seen lightstruck flavor called "catty" - incorrectly - thus confusing it was "skunky")... Check out the various BEER FLAVOR WHEELS on the 'net .

 

as a corollary to the dark malts point; pale malts can produce more precursors to off flavors (that emerge with varying degrees of age) such as diacetyl or pentanedione. gotta consider the color of the glass the beer might be packaged in, too, in terms of what might happen. not to mention the packaging methods (big places tend to have much better practices than smaller places when it comes to oxygen ingress during/throughout packaging). I am familiar with the various charts, but only persoanlly use them as a general guideline and not as fully descriptive (much less PREscriptive) for every type of beer (that we brew, or otherwise...just too many variables out there)

 

Looking through my pdf files on the topic, there's also:

The chemistry of beer aging – a critical review
Bart Vanderhaegen *, Hedwig Neven, Hubert Verachtert, Guy Derdelinckx

Best Practices Guide
to Quality Craft Beer

 

betting that access to the Elsevier article is about 10x as expensive as the BA one

 

Well, the BA is free to download - somewhere I found the Food Chemistry article for free as well since I've got the pdf in my files - unfortunately, I guess I just hit "SAVE" and don't normally save the link to the original source - but, yeah, sometimes they do disappear.

(But, that's what Google's for... much more comfortable to sit at home rather than work in some stuffy, florescent-lit library, trying to read microfilm [I get motion sick from them damn things] or microfiche copies and paying 10¢ per page for lousy repros...)

 

anyone know if it's the case that hop extract degrades (or even skunks) slower than hop pellets/flowers/cones? gap in my knowledge...

 

The products themselves or the beer brewed with them? Pretty sure the hop extract manufacturers suggest they are good for years:

(Of course, it was common 75 years ago for hop dealers to still be selling the previous years' harvested dried/baled hops).

Have never seen anyone claim the use of extract instead of whole or pellets extends the shelf of life of the beer itself (but, then, examples of brewers admitting to using extract had been very rare up until recently). I have an interview with a Schlitz brewmaster claiming they used extract because of its longer shelf life "...natural hops can spoil when traveling or get stale but extract is taken when the hops are all fresh and doesn't spoil easily".

And, of course, re: "skunking" - there are the so-called "light-stable" hop extracts, like Barth-Haas' Redihop:

.

 

yeah...didn't mean to imply beers as a whole would hold up longer, but maybe hop character? it's a fairly major ""scandal" in germany that the big places use hop extract. I suspect some may use the ones that protect against skunking but I'm not certain.

 

Yeah, I think there are a lot "beliefs" in that area, but I've never seen anything concrete. It's sorta like the current trope that "Cans keep beer fresher than bottles" - yet have never seen a brewer have different shelf life for cans vs bottles...

Yeah, I'd say the US macro industry went through the same thing in the 1980s but they now freely admit it.
(Check out PABST's circa 1970s brewing diagram for one example).
Now, many the "craft" brewers seem to still be reluctant to say it...

I'd don't know - IF you're using extract, why not use the "light stable" stuff? Seems nuts. I'd guess Corona and Modelo Especial would be examples?

I was surprised recently when I was researching that new Bitburger/Sierra Nevada beer,Triple Hop'd Lager, to read the keg (but not the can) label and see "Hop Extract":

 

I'll get flamed for this. I applaud you if your efforts actually make a difference, but all of the science in the world can't turn something subjective into something objective. We're not talking about the rate of salmon spoiling. The dates on beer are a business decision. If the brewer feels that their product is still fine at 6 months or 24 months, that's up to them. If their dating policies cause many customers to be unsatisfied, then the brewer will face the business repercussions. If marketplace realities dictate that brewers use a longer shelf life than they'd ideally want for their product, then that's something that they've decided to live with as businesspeople. You can do what you want as the purchaser.

 

YCH says they last for years, but those are often for bittering.

Some varietals extracts are being made, but I don't know how well the aroma holds up.

 

Yeah, but I was surprised by the OP's comments about not just the length but the variety of different lengths of recommended shelf life periods and the fact that so few note a bottling date. So, if he, like most of us, use our own cut-off period for buying beer, it ain't so easy if you don't know what that "BEST BEFORE" date is based on.

Seems to me here in the US it is mostly German beers that commonly have both dates, exactly 1 year apart - so you think to yourself, "Oh, thanks for not making me do the math on that one..." .

I didn't, did I . Hey, 'cause I basically agree with you. I've been bitching about no dates, confusing dates, illegible dates, unknown code methods, for longer than some folks here have been drinking beer but lately I do think, after reading yet another post ranting about missing/hard to read/old date codes, "Yeah, well, just buy something else...".