It is tragic when good people do bad things to excellent coffee. Some just make me cringe, like storing beans in Lexan dispensers, leaving naked beans to soak up the sun, degrading by the second, while smearing the evidence – all those essential, beautiful oils – all over the plastic on display for the world to see. That is just no way to treat a bean, or any bean for that matter. Or, how about beans displayed in those huge open barrels, like prize pickles at a weekend farmer’s market. Ah, but those coffee aromas…so good! Make that, so bad, because those aromas delighting your nose are now gone forever, taking flavors with them on a nonstop flight to nowhere. While knowing how little is understood about grinding outside of coffee professionals, who would ever turn over the keys to the store’s grinder to a once-a-month customer, just itching to over-rev that machine like a souped-up Vespa, turning everything in its path to dust? “Self-grind-and-bag” should come with the risk of prosecution.
I could go on and on.
Like so many things gone sour, these crimes to beans come down to a lack of knowledge; in this case, knowledge about the dynamics of roasting and what happens soon afterwards. When I lecture on this topic, I start by explaining that roasting, like any chemical reaction, neither destroys nor makes anything, but rather, it transforms just about everything. Subjected to heat, small, hard, green beans, with hardly a trace of aroma, metamorphose into bigger (yet more delicate), brown, fully aromatic creatures, kicking off lots of (in coffee’s case, precious) carbon dioxide along the way.
Assuming a good roast, the problems start there, with roasted coffee losing up to 40 percent of its essential, delightful aromas after only eight hours’ of exposure to air. As I have written before, how much degradation actually occurs stems from an epic battle between coffee’s own Cain and Abel: a pair of sibling processes with polar opposite effects. “A” is for aging (and Abel), the do-good brother inspiring positive, naturally occurring chemical and physical steps that, over time, optimize coffee’s aromas and flavors. And then there is staling – coffee’s Cain – which brings negative, yet still natural changes to aroma and taste, wreaking havoc on his brother’s good works.
For about the first 24 hours after roasting, coffee beans contain too much carbon dioxide to be brewed properly, especially if the brewing method is espresso, because their aromatic components are unstable, producing a less flavorful liquid than fully matured roasted beans. (Think about a Polaroid picture about 30 seconds before full development, it is just a tad out of focus.) However, on the flipside, beans that are not properly preserved or used too long after roasting lose too much carbon dioxide, surrendering too many volatile aromas in the process and making for weakness in the cup.
Which brother wins any given post-roast cage match comes down to one thing: packaging. When it comes to bags, one-way valves are like good insurance policies; you should not go through life without them. Along with protecting its contents from moisture and light, like any opaque package, bags with valves allow coffee to be packed soon after roasting without forced degassing, which is never a good thing. The valves keep essential carbon dioxide in the bag that forms a barrier against oxygen and its degrading effects, slowing down staling. Meanwhile, the valves do let out trace amounts of carbon dioxide to keep bags from exploding under normal rises in atmospheric pressure.
However, that escaping gas, minute as it may be, takes with it some essential, volatile aromas. Knowing that time is of the essence, some roasters, for example Intelligentsia, stamp roasting dates on bags, which is useful and noble if retail staff is vigilant about discarding post-prime bags. Date stamped or not, I tell my students to place the valve close to their nose and squeeze the bag gently to let just a little gas escape, then give a little sniff to see if good, fresh aromas are in evidence.
Non-valve bags are essentially containers without seals; for all intents-and-purposes open, rendering forced degassing unnecessary. Coffee can be put in bags soon after roasting, and indeed, some purveyors, such as Blue Bottle, bag and ship coffee the day it is roasted. But beware: too young and carbon dioxide-rich beans will produce overabundant crema in the cups of espresso lovers – yes, there can be too much of this good thing – while beans degassed too long are degraded and weak, producing insufficient crema.
And now for that question for the ages: to chill or not chill to extend beans’ useful life? While I used to favor refrigeration under certain circumstances, my thoughts on this topic have recently evolved with research showing that the oxidation promoted by refrigeration outweighs the good it does to stunt degassing. Whole beans kept in airtight containers away from light in a dry place, is my new recipe. (Better yet, just invite over all of your friends, empty and grind the contents of a full, primo bag at peak potency, prepare it your favorite way, and enjoy. Coffee is, of course, a social beverage!)
Which finally brings us to cans, the most misunderstood of all coffee storage vessels. It is a shame that vacuum packing has gotten a bad rap because it outperforms any bag at protecting roasted coffee from moisture, oxygen damage, and light. However, vacuum packing carries one damaging, inescapable requirement: the need to completely degas coffee before sealing to keep the can from expanding or possibly even exploding. Essentially, shelf life’s gain is aroma and flavor’s loss. (For the record, I think that vacuum-packed “brick” bags are the best application of this method. Look for bags that have somewhat lost their brick-like shapes: a good thing, indicating that some flavor-preserving gas remains inside.)
Some innovation-minded roasters use a pressurized canning method invented by Francesco Illy more than 80 years ago that, in my opinion, still reigns supreme. After drawing out air, his schema introduces inert nitrogen gas to push out residual oxygen, while upping pressure in the can. This process creates a natural, flavor-retaining barrier that is far stronger than any in a valve bag, trapping the vital volatiles that normally escape into nothing. The key period is the first 10 to 15 days after packaging, when a strong aging effect takes place that actually improves coffee quality, the high internal pressure spreading natural oils around the coffee cells (see photo). Flavors are, in effect, infused into those oils, ready to be extracted during the brewing process.
OK, so I am partial, but I can tell you in good faith that my position on pressurization is supported by sound science and years of validating research.
Bag, can, Grecian urn…you name it…understanding the dynamics of freshly roasted coffee is critical to making sound decisions about packaging.
Giorgio Milos is illy’s award-winning Master Barista and illy’s North American Barista in Residence who regularly ventures beyond the cup to study the biology and chemistry of the coffee bean, continually striving to master the beverage that is his passion and profession.