Got Fresh Beans?

There's a good thread on coffeed.com discussing a technique that Scott Rao promotes in his book: you grind a pot's worth of coffee, then let the grounds sit for a while before brewing them. It's supposed to improve the result by reducing excess amounts of CO2 in the coffee, therefore allowing better water/coffee contact.

This technique is, of course, heresy; everyone "knows" that you always should grind immediately before brewing!

A big part of the Coffeed discussion revolves around what exactly goes on with the coffee in the interval between roasting and brewing, and how pregrinding makes these things happen much faster (desirable happenings as well as undesirable).

Whether the coffee is preground or not, there are a great number of terms used to describe the changes that occur. You know some of the typical ones: "degassing," "aging," "staling," etc. The variety of terms we use reflects the complexities and controversies that surround the aging of coffee.

In these matters, it's always helpful to see what Illy says in Espresso Coffee: The Science of Quality. And sure enough, he has quite a bit to say. Bear in mind, even though it's edited by the famous Andrea Illy and presented as "Science," everything in the book should be subjected to our own verification.

Now, for the sake of discussion, I'm going to stick my neck out and try to distill this controversial subject into a few oversimplified, over-opinionated and (hopefully) over-the-top paragraphs! Many of you, especially those who are more knowledgeable and more widely read than I, will scream bloody murder at my inevitable blunders. But it's all in the spirit of free and open discourse, no?

The most obvious thing that goes on as beans "age" is degassing: the CO2 produced in the roast process is gradually lost. This is usually considered to be a good thing, because the copious amount of CO2 in very fresh beans makes good extractions problematic, and most people don't enjoy the extra "fizz."

Unfortunately, as CO2 is lost, so are many volatile compounds that give coffee its distinct and delightful aromas. According to Illy, CO2 and volatiles leave the coffee at about the same rate. After 50% of the CO2 has departed, for instance, 50% of the desirable aromas have also left. It appears that this is a win-lose situation: we want to get rid of some CO2, but we inevitably lose some aromas. More on this later.

Another undesirable process that occurs during bean aging is oxidation. Many compounds that are key to imparting fresh coffee aromas and flavors are chemically unstable, and they are very susceptible to oxidation. (This is what Neil Young was referring to when he said, "Rust Never Sleeps.") To the extent that we takes steps to exclude oxygen from our roasted beans in storage, we can avoid a lot of the flavor deterioration.

The aging process includes oil migration, the familiar phenomenon by which coffee oils move from the interior of the roasted beans to the outside, where they can be easily (and undesirably) oxidized. CO2 pressure seems to be the main driving force here.

Another phenomenon, this one unfamiliar, is what Illy describes as the incorporation of volatiles into the structure and oil content of the bean. It means that aromatic volatiles are adsorbed, absorbed or dissolved in various coffee bean structures or substances. This is interesting and desirable, because it tends to save and protect the volatiles from being lost and/or oxidized.

Given all the factors that detract from the quality of our beverage, how can it be that we ever manage to have a good cup? Probably everyone who visits this site has had a least one good coffee in their lifetime. Even Howard Schultz got one when he made his now-famous visit to Cafe Grumpy!

Well, as far as the CO2/volatiles "win-lose" situation is concerned, it's a matter of finding a good compromise. There appears to be plenty of space along the timeline where enough CO2 has departed and enough desirable volatiles are still left to make a great cup. In fact, there may be many points where the balance between the two yields different but still very good results; this happy result may occur surprisingly far down the timeline.

In addition, there are several techniques that attempt to optimize the situation of degassing, volatiles loss and oxidation. It depends on how exquisite a job one wishes to perform. They include:

1. packing the coffee in paper bags and allowing the evolving CO2 to displace oxygen

2. packing the coffee in sealed barrier bags with one-way valves that prevent oxygen re-entry after evolving CO2 has displaced it.

3. flushing oxygen out of one-way-valve-equipped packages with an "inert" gas (CO2 or nitrogen) before sealing.

4. performing the procedure in #3, except with a rigid package that retains about a half bar of overpressure before the one-way valve opens. This strategy, which Illy uses, supposedly keeps more oil and volatiles inside the bean where they are protected from deterioration. After 10-15 days in this moderately pressurized environment the beans are supposed to be better than when they started. Wouldn't it be something if it actually worked as advertised?

5. storage of beans at freezing temperatures greatly slows down all the aging processes. Especially when combined with oxygen exclusion, beans can be kept in "almost new" condition for a much longer interval than normal. Thank you, Mr. Sivetz.

6. use of moisture and/or oxygen scavengers: mysterious little packets that say "Do Not Eat" in English and "Are Americans Stupid Enough to Eat This Packet?" in Chinese. They are available in oxygen-consuming and moisture-removing versions, and they never sleep.

Well, OK, now for a few questions:

1. How many roaster/retailers out there follow Sivetz's recommendation to store their roasted coffee under freezing conditions (with or without removing oxygen first)? If not, why not? You don't think it would be worth it? Why not sell "flash-frozen" coffee beans in a sealed bag with the admonition: "Warning! Allow contents to warm 12 hours at room temperature before opening! Once thawed, store in a cool, dry place outside of the refrigerator."

2. How come some very excellent roasters still sell their retail coffee in plain paper bags, with no moisture/oxygen barrier and no one-way valve? Have they tested it and convinced themselves that it makes no difference?

3. Obviously, Illy Caffe has a proprietary interest in promoting their pressurized storage method, but who has independently tested it with their own high-quality roasted beans?

4. How come I'm asking so many questions, and providing so few answers?