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MOISTURE IN COFFEE EQUALS QUALITY

"Coffee prices are currently at peak levels, even higher than the freeze of '94. Everyone I have spoken with involved in coffee is in a frenzied state."

Moisture in coffee beans is frequently a last minute item of concern. However, it is a significant factor in the quality and cost of coffee. Beginning at the time of harvest, moisture is a key determinant of the maturity of the bean for harvest. This maturity has a continuing influence on the quality of the coffee at each of the next steps. It determines the amount of drying needed to stand the rigors of shipping. It is a principal economic factor due to weight loss of the green beans during storage and roasting.

Understanding moisture is one of the keys to the art of roasting and in maintaining consistent roasted products from batch to batch. The effectiveness and efficiency in the final step of the grinding process is dependent on moisture levels.  Processing the bean, the economics of the process, and the taste of brewed coffee are all influenced by the moisture content of the bean, from green to roast to ground.

Determining the Ideal Picking Time
In talking with growers from different parts of the world, I have learned that from the time the bean is harvested, moisture plays an important role. If the bean is not picked when the crop is within the optimum moisture content range, it is at risk of deterioration from environmental conditions.For example, the risk of the discolorationof the beans (loss of the green tint of the beans (loss of the green tint and the development of a musty, whitish color) can be greatly reduced if not eliminated when the harvest is done if the beans are in the optimum moisture range (20-30 % moisture). Measuring moisture in the fields to control harvest schedules is an important element in this first step of the process and has implications for subsequent production techniques.

Finding the Optimal Drying Parameters
Growers need to constantly monitor moisture content in order to determine the best drying time and procedures. For example, green beans in Indonesia will typically be higher in moisture content than green beans in Columbia because of the higher humidity in Indonesia. Consequently, different drying schedules and techniques may improve the drying results.

Frequently, two loads of green beans from the same region have different moisture contents. This may be the result of different drying methods or varying weather conditions. For example, three different growers advertise that they use the gentle drying process. However, the grower in Kenya uses a concrete patio, the grower from Ethiopia uses netting and the grower from Ghana uses the drying table approach. If the process is not monitored by measuring the beans' moisture, wide variations in the resulting moisture content can be expected. The variations in the methods used and the differences in weather conditionin each of the countries would effect drying times. Without a means to measure the changing moisture, wide differences would be expected.

Shipping & Storage
Many exporters and importers have informed me that one of the keys to cost- effective purchasing is knowing the moisture levels of the product at the shipping destination. Moisture levels in green coffee at this juncture not only have impact on processing and taste, but are a significant factor in the price.

During shipping, coffee beans are exposed to wide variations of temperatures and humidity. These environmental changes often result in condensation and other exposure to the source of absorbed moisture. Because it is difficult to control these environmental factors during shipping, obtaining the correct moisture levels at the completion of the drying process is of paramount importance. If the beans are too dry (below 9 % moisture), they will immediately begin to lose flavor. If the beans are too wet (above 13% moisture), they will mold easily.

Get the Best Roast out of Your Bean
During the roasting process, the quality of the beans determine the consistency of the blend and the taste, roast after roast. Knowing the moisture content of the green beans prior to roasting helps the set up of the roaster.

For example, roasting a Colombian with a moisture content of 9.5% with roaster settings of 400 degrees F for 120 seconds produces a standard product. If the next Colombian batch had a moisture content of 12%, the same setting would produce something different from the standard product. With the knowledge of the new batch moisture content, adjustments in roast time and temperature could be made to again produce the standard product.

Measurement of moisture content is a principal way to predict shrinkage. The shrinkage tells you what your bottom line is going to be and more importantly it supports the fact that you are producing a quality product with excess quenching. Knowledge of shrinkage data provides you with realistic factors for determining efficient cost pricing structures.

The Grinding Process
As with roasting, the outcome of the grinding process is dependent on the moisture of the beans. The impact of moisture in the grinding process is twofold. At high moisture levels the beans will not pass through the grinder uniformly and can cause a clogging of the grinders. At lower moisture levels, dry grounds can create static electricity problems.

The grind size also affects the extraction rate of the coffee. The perceived taste of the coffee is affected significantly if your grind-size is larger or smaller than it should be. Even though grind-size seems like a small matter, it is certainly a big factor when it comes to the perceived quality and taste of your coffee.