Think globally, drink locally!    

  Accueil -> Société -> Article précédent suivant   imprimer envoyer détacher  
How does a good beer go bad?

It’s a fact of life: beer gets rank if it gets hot. Light does something to it, and letting a beer get warm after it’s been cold will ruin it somehow. Do we really know this for certain, or is it just beerlore that has been handed down from father to son to teenage buddy without any questioning?

Sitting around talking about it is fun, but I decided to get empirical about it. It’s the science fair project for adults: what really happens to beer under everyday situations?

I began the project with a quick trip to Independence Brewing, in northeast Philadelphia. Brewer Bill Moore handed over two quiveringly fresh six-packs of his Franklinfest beer, whisked off the bottling line the day before and kept under constant dark refrigeration. There was apprehension in his eyes - he knew what I had planned for his beer. I managed to suppress the maniacal giggle that rose in my throat and assured him that it was all in the name of science. I put the beer on the floor of the car, covered it with a blanket and pumped max air-conditioning on it for the half-hour drive home. There I popped open one fresh bottle of malt nectar for a baseline taste.

Gorgeous beer, Bill, and I can easily see why it’s won two Great American Beer Festival medals in the past three years. A fresh, slightly yeasty smell comes through clearly, with malt aroma following on behind. Malt dominates the flavor profile too, as it should, with just a cleansing touch of hop bitterness. There is a bit of graininess which is not unpleasant. The finish is soft and dry, and beckons for another sip. Granted, it’s not as big as a Munich Festbier, but it’s a good American interpretation. This was obviously going to be the high point of the experiment.

Now came the ugly part. I set aside two control bottles in my cool, dark basement, and numbered the rest of the bottles’ caps. Then, with a short, apologetic mumble to the beer spirits, I started being bad to beer. Like The Grinch setting up a bizarre Easter egg hunt, I stashed beer in the oven, in the freezer, in sunlight. Treating beer like this was in conflict with every good beer instinct I had ever cultivated.

The first ones to be mistreated were wedged into the freshly-turned earth of our garden, label down, to catch some rays. I took care to set them at an angle which would catch the sun’s direct light, and checked their exposure through the day. Bill uses pretty dark brown bottles, which offer some protection from beer-zapping light. Set your phasers on kill, men - I gave these beers two days’ worth of 8-hour stretches of direct sunlight. They were doomed.

They sure were! The hiss of the cap coming off brought with it a whiff of skunk, a sharp ’catty’ smell, overwhelming every other trace of aroma. It gets into the flavor a bit as well, even when I hold my nose. It’s a cloying, powerful sensation, and there’s no escaping it.

What happened to this beer? If you want to know about beer science and chemistry in America, you go to the Siebel Institute, in Chicago. The Siebel family has been educating brewers and chemically analyzing beer for generations. I called the Vice-President of Educational Services, Dave Radzanowski, and asked him: What happened to these beers?

"They’re lightstruck," came the short answer. Certain wavelengths of light (those around 5,000 angstroms) can turn a wonderfully aromatic beer into a skunkfest. "Hop oils have a sulf-hydryl grouping in their molecular structure," Radzanowski explained. "When these wavelengths of light hit that, there’s a photosynthetic reaction which changes that grouping to that of the common ’skunk’ aroma. Those wavelengths are abundantly present in sunlight and fluorescent light; incandescent light is not so bad."

Is there any way to protect bottled beer from this photonic invasion? "Clear glass is the worst, green offers only marginally better protection," Radzanowski ticked them off, "and brown gives partial protection. Ruby-red glass would protect the beer completely, only it’s a lot more expensive than brown glass. But fluorescent lights in a cooler could be covered with ruby-red cellophane filters quite cheaply. Most retail displays are disaster areas for beer." By the way, there are less garish filters available that slip right over a cooler’s fluorescent tubes.

High tech is coming to the rescue for clear glass. Beck’s is not only a German brewery, they also own a glass factory and spend fairly heavily on research there. They’ve come up with a clear glass that filters out these "skunking" wavelengths. You’ll be able to do your own research on this soon as the imminent national rollout follows a successful market trial in Rhode Island, among other places.

But what about beers like Miller that come in clear glass without the benefit of German engineering? Why don’t they skunk up something fierce? Miller comes at it from a different angle, making the hop compounds less susceptible to skunking. Darwin Davidson, the technical director for major hop broker S.S. Steiner, explained the process of making the hop extracts Miller uses. Darwin is the technical director, and this does indeed get a little technical, but bear with me.

First, liquid carbon dioxide is run through a bed of pelletized hops. It absorbs the hops’ oils and resins, the key flavor, aroma, and bittering components. Then the carbon dioxide is allowed to evaporate, leaving the extract. Some brewers use this extract, and Davidson said that it will give a very true hop character to the beer. Extracts can be split down further to pure alpha acids, hops oil, and beta acids, the real components of interest to brewers. The oils’ flavor is changed somewhat by the process. The extracted alphas can be "isomerized" (This is what actually happens to alpha acids in the brewkettle, Darwin said), and added directly to the beer for hop character.

Miller Brewing takes a further step. They take the iso-alpha acids and hydrogenate them, much like is done at refineries, by forcing hydrogen through the oils at extremely high pressures. This produces rho-iso-alpha acids, also known as tetralones. These tetralones have intensified bitterness, increase foam stability and retention, and offer a better resistance to sunlight. They would be ideal, only they do not maintain the precise flavor of fresh hops. Hopping rates in mainstream American beers being what they are, this isn’t a serious problem as long as the bitterness is right.

Hoppy beers may seem to fare better when it comes to light resistance, but it’s an illusion. "A heavier hopping rate will mask the skunk aroma for a time," Radzanowski warned, "but when it does burn through it’s really horrid." A lightly hopped beer can go bad fast. How fast? "If you have a beer in clear glass exposed to direct sunlight, it can go skunky in 5 to 10 seconds," he said flatly. "It can happen as you walk across the street. It’s that fast."

Next up on my torture calendar were two frozen Franklinfests. Everyone’s done this once or twice, stuck a beer in the freezer to chill it fast and forgotten it, left beer in a garage in the winter. I let the beer freeze up until there were solid beersicles inside the bottles, then let it slowly thaw in the fridge.

It tastes a lot like the baseline beer: malty, smooth, just a touch of hops. The finish seems a bit longer, and the carbonation somewhat spikey. The mouthfeel is perhaps a touch creamy, fuller.

If I had not known this beer had been mistreated, I might not have guessed it. This was a quite subtle effect, and not all unpleasant. This is actually how American breweries make ice beer. They freeze it, then thaw it, without removing any ice. (Canadian brewers skim some ice, raising the alcohol levels, but this practice is considered distilling in the US and requires a distiller’s license.) What’s the point, and what’s going on here?

Siebel to the rescue again. "Freezing puts a denaturing pressure on the proteins in the beer. As they denature they come out of solution and create a haze, or even flakes, in the beer," Radzanowski told me. Denaturing means the proteins’ structures are being ripped apart. "Repeated cycles of freezing and thawing have a greater effect."

Haze and flakes sounded like some really old beers I’ve seen, and I said so. "That’s right," he said, "It accelerates the aging process. In fact, we use freeze/thaw cycles as a tool to predict a beer’s shelf-life." One cycle will start to bring those proteins out of solution and change the texture and mouthfeel of the beer. That’s why ice beers taste somewhat smoother, and where eisbocks get their remarkable silkiness. Repeated cycles are not as beneficial.

Next I did some repeated cycles of warm and cold, leaving the beer in a 120 degrees oven for an hour then chilling it for two hours in the refrigerator. I wanted to simulate picnic beer: the sixpack you put in the fridge, take to the picnic, forget to get out of the car, leave in the sun, then take home and refrigerate again. After six cycles, I chilled it and split it with my wife.

This is wrong from the get-go. There was a distinct aroma like that of cooked vegetables. The beer had an increased sweetness, which became cloying in the finish. We couldn’t find much evidence of hop at all. The wife was not amused, and we dumped the beers.

I thought I was onto something here, that hot/cold cycles would really crock the beer. After talking to my Siebel man I guess I should have stuck to room temperature. "Warm/cold cycles will affect a beer," he explained, "but it’s really the warm part of the cycle that’s doing it."

"Heat is like over-pasteurizing a beer," Radzanowski said. "It ages it rapidly. The heat caramelizes whatever sugars are in the beer, giving it a differently sweet taste." Heat will also greatly amplify any hint of off-flavor, like dimethyl-sulfide, or DMS (that’s my cooked vegetable odor).

Last up was a beer I actually cooked. I gave it 6 hours in a 140 degrees oven to simulate beer left in a car’s trunk in the heat of a summer day, or beer left in an uncooled warehouse for weeks. I expected something not so nice, and I wasn’t disappointed.

The beer did have a surprisingly big head, one of the best of the bunch. It smelled like a can of creamed corn, with a scary whiff of gutterstink. The flavor was not as bad as the smell, but there were definite changes in the sweetness again, almost ’curdled’ malt flavors, like salt water taffy from two summers before.

This was my hot/cold cycle beer’s big brother, HeatBeer. The DMS Radzanowski had warned me about was here in abundance. This would qualify for a homebrewer’s demonstration of off-flavors. In fact, Siebel does such a demonstration at brewing conferences, setting out samples of deliberately mistreated beer. A brilliant demonstration, and one which every beer consumer, retailer, and wholesaler should experience.

I was glad to see the last of these poor beers gone, down the drain. After I poured them safely away, I brought out one of the two control beers, left in the cool, dark cellar. Just the kind of reward my evil deeds deserved! Ah, that clean aroma of malt was back, as was the good malt-mouth and dry finish, and that little nip of bitterness. Just for one last test, I let the last control bottle sit in the dark for a while longer, then chilled it and consumed it. Three weeks of good conditions appeared to have taken nothing from it. Bill, your sacrifice went for a good cause: I’ll never let beer sit in the heat or the light again!

We do have allies in the fight against bad beer; the brewers themselves. The most consumer-friendly weapon is dating, either packaging dates or "best by" dates. The latter is what Boston Beer Company uses, and has since 1987. "It’s been a crusade of mine for twelve years," Jim Koch said. "When I started, people told me "Are you crazy, don’t you realize how much that will cost?" How much does it cost in sales when you sell stale beer? If the brewer doesn’t have freshness dating, he doesn’t hurt the wholesaler or the retailer, he hurts the consumer."

Koch’s beers are dated "Best By" with a date four months after bottling. "The vast majority of beers are good for about four months," Koch said. If the beer should happen to reach that date while still sitting on the shelf? "We pull the stale beer out of wholesale and retail and destroy it," Koch confirmed. "I view freshness as another cost of making sure the consumer who buys Samuel Adams is getting great beer. It’s an ingredient like hops or malt, and it costs money. "

Anheuser-Busch also uses dating, but approaches it from the other end with their much-advertised "Born On" dates. I asked Dan Hoffman, Director of Budweiser marketing for A-B, why "Born On," and where the term came from. "Why was easy," he laughed, "’Bottled On’ didn’t look right on our cans! The truth is, we wanted something proprietary. A lot of the others sounded like something from the pharmaceutical industry: "Packaged On", "Sealed On". August Busch IV actually came up with "Born On", and it has a real friendly feel."

Why put a packaging date instead of a "best by" date? "Our opinion is that a pull date doesn’t really mean anything," said Hoffmann. "You set it out whenever you want, and who knows what that is?" A-B puts the packaging date on the package, then lets the consumer know that it’s good for 110 days after that date.

"Part of the success of the program," Hoffman said, "is that we’ve raised the bar for the industry, and that’s good for beer. We feel good about that." There was some worry among retailers that customers would start going through the beer on the shelf, looking for the beer with the latest date. Hoffmann acknowledged, "One of the big fears in our wholesaler network was this problem. It didn’t happen at all. It’s more of a check after the purchase. As they enjoy it they take a look. It’s almost habitual for some people. It didn’t prove to be the issue our retailers thought it would be."

Obviously we can’t all get our beer literally brewery-fresh and keep it obsessively safe. Compromises have to be made. But it’s very much worthwhile to put a little effort into keeping your stock correctly. Remember, just six hours in the heat did in a beer, and sunlight is even quicker. "Best by" and "Born on" dates mean nothing if a beer is not kept well.

If you don’t do this, a growing number of consumers will notice. Most beer-lovers I know will be very suspicious of a store that displays beer in a sunny window. Some may bring it to your attention, some may just go elsewhere. They won’t buy wilted produce, and they won’t buy skunky, old, cooked beer. Get out in front and educate your customers on all the good things you’re doing for their beer. It’s working for Anheuser-Busch and Boston Beer, you can make it work for you, and everybody benefits.

Lew Bryson

Beverage Business - 10 November 2000
Molson en infériorité numérique
It’s nearly beer
La "fontaine de bière" suscite de nombreuses critiques dans un contexte marqué par le besoin d’économiser
Careers in Beer
Les brasseurs veulent limiter la consommation de bière par les mineurs
Dark Lord, Alimony Ale, Old Ruffian: Here Are the Brawling Beers
Hey Czech brewery — this Bud’s
Strange brew
Eichhof : légère augmentation de la consommation de bière en Suisse prévue
Les jeunes boivent moins d’alcool
Keeping Beer Fresher
A l’Echoppe médiévale, la bière se fait mousser au pays du vin
La chope change
Drinkers Can’t Judge a Beer by Its Taste, Study Finds
Reconnu saveur de l’année 2004
Beer powder taps flavor, easy handling
Un verre qui garde votre bière au frais
Can real men drink light beer?
Foul Brew
Reconnu saveur de l’année 2003
RFID Monitors Beer Temperatures
The Outdoor Beer Fridge
Coors Light Promises No More Warm Beer With the New Cold Activated Bottle
Heineken en tête, les brasseurs battent clairement le marché
Comment servir la bière ?
Un fût de bière autoréfrigérant
Un verre qui refroidit la bière instantanément
Record ale sales
Chilling news for beer fans
Nouveau : le pack de bière glacé !
      sommaire | haut de page | à propos | résumé