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The bean grader's art

Ever wonder why one bean makes it to your local specialty shop and another doesn't?

Long before you sip a delicious cup of dark ambrosia, coffee graders make hot and tiring journeys, face insects and hostile governments and endure weeks of frustration and danger to bring you that favorite brew.

Ok, maybe it's not quite as adventurous as that, but graders do lead interesting lives.

Coffee is graded long before it makes it to the loading dock. The task is carried out by someone called a 'Green Coffee seller'. No, that job has nothing to do with any environmental movement. It's simply a reflection of the fact that beans are 'green' or fresh, before they're made brown by roasting.

Beans are carefully examined for a number of traits.

They need to be fairly uniform in size and similarly shaped. This is important to help ensure an even roast. Smaller beans roast differently than larger ones. When the size of the bean differs the roasting time can't be adjusted properly, since some will pop and brown before others.

Graders look for similarity of color, as well. Uneven coloring suggests that beans have dried at different rates. It also indicates that beans may have been mixed from different cultivars, again leading to inconsistency in roasting and flavor.

Beans have to be separated by geographic region grown and by cultivar in order to achieve the appropriate final result. They need to be harvested, processed and dried separately for the final product to be a fine brew.

Beans are best when they're processed soon after harvesting. Coffee beans undergo a kind of fermenting process that will initiate after harvesting. The process isn't like fermenting wine - turning sugars into alchohol, but it nevertheless produces unwanted compounds. Drying prevents this from beginning.

Many processors will float the beans in water to separate out defective beans, since different density beans will float at different levels. But finer beans result from a more time-consuming process called 'dry processing'.

Dry processed beans have a brown 'silverskin', called a fox bean in Brazil. If the silverskin can be removed by simple rubbing, it's not a defect, but evidence of this dry process. Under ripe beans, though can also have a silverskin, which can't be removed by rubbing. Such beans will result in a coffee with a sour taste.

Drying beans is an art all by itself. Estates often boast proudly of the skill and care taken during the process. As well they might. Improper drying often shows. Economics sometimes encourages processors to use harsh mechanical drying techniques. Drying the beans too rapidly or failing to turn them frequently enough can result in beans with an uneven, mottled appearance.

Beans that have been properly dried will first spend time on a 'patio', to dry the skin, before they're fed to the mechanical dryer. Truly superior beans will have spent several short stints in the dryer at around 40°C (104°F), rather than one long one. The result is an even color and just the right moisture content.

There are a few other aspects graders will look for.

Beans can have a white edge as the result of inadequate drying or being stored in too humid conditions. The result will be a bland cup and graders are on the lookout for it.

Good Arabica coffee beans, the type used in fine coffees, will have an even, bright appearance.

Lastly, they smell the beans. Good beans will have a fresh aroma, but they also try to detect what's absent along with what's present. Any improper processing will add a smoky or musty tinge that you don't want in your cup.

So before you sip that fine brew, take a moment to sense the fine aroma and lift a cup in thanks to bean graders.

Judging coffee beans the barista way

A 'barista' is someone who makes coffee drinks as a profession. Naturally, that experience will shape how beans are judged.

'Cuppers' (coffee contest judges or professional tasters) and company buyers share the barista's goal of finding beans which produce a great drink. But it's the barista who stands in front of the final consumer every day and receives immediate feedback on the success or failure of those efforts.

So, let's find out what the barista thinks about a bean and its product...

Roughly 70 countries now grow coffee from which beans are produced, from Africa to the Middle East, from South America to the Caribbean and over to Hawaii - all within a band about the equator of roughly 25 degrees north or south.

Not surprisingly then, given the differences in climate altitude, equipment and techniques - and a host of other factors - beans from different countries show marked differences. Even different plantations will often have drastically different products.

Even so, coffee plants come in two main categories - arabica and robusta. With half the caffeine of the robusta, the arabica is used almost exclusively for the finest coffees. Its beans are more flavorful and full of aroma.

Since coffee grows better at higher altitudes the Milds - arabica beans from plants grown at 3000 feet (915m) or above - are to be preferred. 'Brazils' by contrast are arabica beans grown in Brazil, but at a much lower altitude.

Beyond that, judgments will differ depending on whether the consumer intends to 'roast their own' or not. Unroasted beans are green, soft and have a vegetative odor, which is normal.

For those seeking roasted, the categories broaden. There's a light or 'cinnamon' (named for the color of the spice; nothing to do with the flavor). These are acidic and highly caffeinated.

The medium or 'American' roast is slightly darker and enormously popular since it's the degree used by the major coffee vendors (Folger, Yuban, etc). Not a quality cup by most barista's standards.

Dark or 'City' roast is what is seen in many specialty shops, where the process has reduced the caffeine and acid taste. The result is a less bitter, often sweeter cup. This is what's generally used for the average espresso.

Next in line is the 'French' roast, so named because the French tend to prefer their coffee more full-bodied. The beans will appear very dark brown and have an oily texture or sheen. Look carefully and sniff so as not to confuse these with beans that have merely been burnt.

Darkest on the drinkable scale is the 'Italian' roast, often used in specialty espressos. The deep brown color and pungent aroma are distinctive and make a fine cup.

As one goes down the scale of color, the cups made from these beans will be increasingly less acid and more sweet. This is a consequence of the carmelization (browning and thickening into syrup) of sugars resulting from the roasting process. At the same time some of the caffeine - a bitter chemical - is burned away, producing a mellower cup.

So, next time you shop for beans give a thought to the barista who stands daily in front of an array of choices and with an arsenal of machines. That person knows beans.