Sunday, November 06, 2005

Coffee Storage: Cupboard, fridge or freezer?



Sometimes I hear something that is different from my long-held perceptions, and want to find out the real story. This time the issue was coffee storage. The KCRW Good Food program of October 15 had a visit from their supermarket guru, Phil Lempert to talk about supermarket coffee. He said that putting coffee in the freezer is a very bad idea (the reasoning is provided below). I had always thought that freezing coffee might help reduce the degradation, so decided to determine the expert consensus.

First, some words about the basics of coffee roasting and the subsequent degradation. A green (unroasted) bean has a very long shelf life---months or even years (many large coffee producers have huge warehouses to store green beans until the market is most favorable for their sale). When the bean is roasted, it undergoes many changes---the so called browning reactions that convert the carbohydrates and proteins into a multitude of flavorful and aromatic compounds. These compounds are vulnerable to deterioration through volatilization, oxidation and rancidification via exposure to oxygen, light, heat and moisture. In addition, carbon dioxide---which provides body and bouquet to coffee--dissipates. Grinding breaks the cells of the coffee bean, thus releasing encapsulated aromatic compounds and exposing essential oils to oxygen.

I consulted a few sources on coffee storage, and there is significant disagreement whether coffee should be kept in the freezer or at room temperature. There is agreement, however, that coffee should be protected from moisture, light, heat and air. In addition, the experts agree that storing beans in the refrigerator has negative consequences because the beans can pick up unwanted flavors from neighboring food and drink (or ex-food!).

Several sources recommended putting coffee in the freezer for storage because the low temperatures slow down the degradation process. However, this method creates the possibility that moisture will condense on the beans when the container is opened (think of the water that condenses on a glass of iced tea on a hot day), thus harming those that are put back into the freezer. To prevent condensation, beans could be frozen in small containers and allowed to warm to room temperature before the container is opened. In other words, when you buy a pound of coffee, pack it into small packages that contain the amount that you grind at one time.

A few quotes from books and the web:

In The New Kitchen Science, Howard Hillman writes "If you must store your coffee bean supply for more than two weeks, freeze it in a well-sealed moisture-proof container. Beans can go directly from freezer to grinder to coffee maker."

Corby Kummer's conclusion in The Joy of Coffee is that "refrigeration virtually guarantees off-flavors in brewed coffee, and that coffee never tastes quite the same after it has been frozen--even if freezing is far better than refrigerating. But if you can't use up your beans within two weeks or so, settle for putting them into the freezer, whole and tightly sealed, in either a glass jar or plastic container."

The Starbucks web site says: "Think of coffee as fresh produce. The enemies of coffee are oxygen, light, heat, and moisture. To keep coffee fresh, store it in an opaque, airtight container at room temperature. Storing coffee in the refrigerator or freezer for daily use can damage the coffee as warm, moist air condenses to the beans whenever the container is opened."


Phil Lempert's Coffee Chat News writes:
To preserve the integrity of the flavor of high-quality coffee beans, you must make sure to avoid moisture, air, and heat. Select containers that are tightly sealed, made of ceramic, stainless steel or opaque glass and store at room temperature.

Avoid containers that are aluminum or plastic because those materials can contaminate your coffee and give an “off” taste. If you are storing your beans in a clear glass jar, make sure to place it in a dark area of your kitchen to avoid light, which can fade the color and the flavor of the beans.

Never refrigerate or freeze coffee beans - the temperature and moisture will “shrink” the oils and crack the beans. The result is a severe loss of aroma and flavor.

The Peets web site answers "How should I store my coffee?" with
We recommend that you keep a week's worth of coffee in an airtight container at room temperature. For longer storage, keep it in the freezer. Packages of frozen coffee should be opened as infrequently as possible. Whole beans will keep up to four weeks, but ground coffee should be brewed within a week or two. Buying small amounts frequently and grinding your own beans is the best way to enjoy fresh coffee.



A final note about the nearly fraudulent labeling "vacuum packed for freshness":
After roasting, beans start to release carbon dioxide (CO2), with a released volume that is about 3 times the volume of beans. If beans were canned or bagged immediately after roasting, the release of CO2 could damage the can or bag. Consequently, most packers let beans sit for 12 hours or several days to allow the off-gassing process to go to completion (or just a few hours for ground coffee) before packing into the "vacuum sealed for freshness" packages. In other words, the packers allow the coffee to go stale before packing it!

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5 comments:

Anonymous said...

If a coffee mixture will loose its flavor after being ground then you should change coffee mixture.

Where I come from, Italy, coffee is sold ground in vacuum packages (or more expensively in metal tins) of 250g (1/2 pound ca) each. A pack lasts 1 to 2 weeks and keeps a very good flavor. I usually transfer it to an airtight container (an old Illy coffee tin, in fact) and keep in the fridge. My tastebuds (but it could just be my neurons :-) tell me it does preserve the taste.

Of course, having items in their "walking" phase in the fridge may rub off on coffee (in fact, used coffee is very good at "refreshing" the fridge from smells), but this would not occur if you use a proper air-tight container and use your coffee quite often (also keeping your fridge clean may help).

The nice thing about grinding coffee, is the smell. Indeed, any kind of coffee has a relatively good smell when ground. But good quality coffee should retain those flavors in the grind mix. In fact, the better the quality the less the need to have it grind before use. Arabica-based roasts are considered higher quality for this (and for their lower acid contents than Robusta). In fact, a good quality mix should contain 50%, at least, Arabica. This you can store it in the fridge, in the freezer or in the cupboard (as long as it doesn't get light and water, I believe there is no difference).

Anonymous said...

the anonymous italian should be embarrassed by the amount of garbage he just spewed forth. the loss (evaporation) of aromatic oils and the oxidation of the oils that remain within the ground coffee are both physical processes that occur regardless of the "quality" of the bean. Saying that good quality coffee does not need to be freshly ground is like saying an expensive tennis racquet doesn't need strings. Seriously man, what planet are you from? And don't say: "italy".

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Anonymous said...

Thanks for the thoughtful discussion on this topic. This was one of the best pages i got on a google for "coffee storage". I appreciate the citation of references and objectivity. che

jess duncan said...

interesting stuff, thanks for the info!