The processed green coffee bean is usually exported in its unroasted state because it is less prone to deterioration than its roasted counterpart, but environmental and other factors can all too easily impact the quality of the end coffee product.
Green coffee beans remain in a fairly stable condition if stored in a cool, dry place and will not start to deteriorate for twelve months or more. Ideally, the beans should retain the 10 to 12 percent moisture content achieved in the final stage of processing until the moment roasting begins, but less than ideal temperature and humidity levels can often cause moisture absorption or additional drying, resulting in a reduction in the quality of the beans. The optimum temperature in which to store green coffee beans varies greatly according to different sources, but most agree that the beans should remain in relatively cool conditions, and no higher than 68 to 77°F (20 to 25°C).
During transportation, and shipping in particular, coffee beans can be subjected to huge fluctuations in temperature and air humidity, with condensation being the probable outcome. Condensation is a major enemy of coffee exporters, because it can lead to the growth of mold and the destruction of coffee flavors—and at worst, irreparable damage to the entire shipment. Even if they are dried to the safer end of the requisite moisture level during processing (that is, less than 12 percent), adverse environmental conditions can nevertheless cause the green beans to absorb enough moisture for mold to grow.
The roasted bean, by contrast, is much less robust and can start to develop a stale aroma and flavor only two weeks after roasting, as the lipids present in the bean oxidize. For optimum flavor and freshness, roasted coffee should be consumed before this process begins, having been safely protected from air, moisture, heat, and light (see here).
Most people assume that green coffee beans are unpalatable until roasted, but different cultures have long been brewing or using green coffee beans in a variety of ways.
Green coffee beans are one of the richest dietary sources of chlorogenic acids, which are highly effective plant-based antioxidants. Furthermore, studies have shown that these chlorogenic acids are also highly bioavailable—in other words, they are easily metabolized by the human body.1 For this reason, green coffee extract has been used extensively in nutraceuticals—various nutritional products and dietary supplements purported to provide health benefits. Green beans are currently touted as a treatment or aid for everything from heart health to weight loss, and while these beans may not exactly be the “miracle cure” they are claimed to be, they have been proven to provide some certain health benefits.
Some human studies have indicated that green coffee bean extract may reduce hypertension,2 and other human and animal studies suggest that it holds promise in helping combat excess weight and diabetes.3 Certain trials have shown that green coffee extract can help reduce the weight of pre-obese adults and prevent obesity in overweight adults; others have linked coffee consumption with a decreased risk of type 2 diabetes. While these claims are yet to be validated by in-depth studies, it cannot be denied that the potentially beneficial chemicals and compounds found in coffee beans are present in higher concentrations when in their unroasted state.
You can buy green coffee beans for roasting at home so that you can create a coffee tailored to your own tastes and specifications. However, to make sure that you start with a good-quality product, you need to know how to recognize defects in the unroasted bean.
A number of defects can be found in green coffee beans as a result of problems or faults occurring in the various stages of growth, harvesting, or processing. Some of the more important ones to look for are detailed below.
As the term indicates, these beans are black and opaque, and they impart a rotted fruit, sour, moldy, or dirty flavor. They are classed as full black if more than half the bean is affected, or partial if less than half is affected. This defect is caused by overfermentation due to overripe fruit or substandard processing conditions.
These beans are yellowish/red/brown and impart a vinegary, sour flavor. The bean is classed full sour if more than half is affected, or partial if less than half is affected. This is one of the worst defects to occur in coffee beans, because a single full sour is thought to have the ability to contaminate an entire pot of coffee.
When broken open, these beans produce a rotten smell with a flavor to match, usually indicating bacteria or mold contamination that may be caused by overfermentation. These beans have the potential to infect and contaminate a whole batch of beans, leading to the ruination of a large quantity of “healthy” coffee. Unfortunately, this type of defective bean is one of the most difficult to detect, because it usually looks normal in external appearance.
It is regarded as a batch defect when a consignment of green coffee beans is found to contain large- or medium-size foreign objects, such as sticks or stones.
POD/CHERRY If a bean makes it through to the final stage with the fruit, or “cherry,” still attached, the batch is considered defective; this could be due to improperly maintained or adjusted machinery.
Similarly, improperly maintained or adjusted machinery can result in the parchment layer remaining attached to the fully processed bean
HULL Again, improperly maintained or adjusted machinery can cause traces of dried pulp to remain attached to the fully processed bean.
INSECT DAMAGE These beans exhibit marks or holes where insects have bored into the fruit, laying eggs inside that develop into larvae. The affected beans can impart a dirty, moldy, or sour flavor.
Small beans with a wrinkled, raisinlike appearance are the result of a water deficiency in the fruits’ development. They impart a grassy flavor when present in sufficient quantities and do not darken as much as others when roasting.
There is no single, universally adopted international grading and classification system for green coffee, although many countries defer to the protocols detailed by the Specialty Coffee Association of America Green Arabica Coffee Classification System (SCAA GACCS). This takes into account the correlation between cup quality and defective beans, but because of the vast number of factors that need to be taken into consideration it is still not a perfect system.
Although grading protocols vary among different countries, most take into account aspects of the following when determining the grade of a bean: its botanical variety, the region and the altitude in which the bean was grown, the method of processing, size, shape, color, density, defects, and cup quality.
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