As a natural product, coffee is subject to differences in flavor depending on species and variety of plant, other agricultural factors, processing, roasting, and packaging. A wide variety of potential flavors and qualities can result. Coffee is constantly changing in all its forms, from green to roast to brew. In order to maintain a consistent level of quality for sale (or for consumption), one needs to understand the nature and rate of these changes to make appropriate business decisions about the quality of product being served or sold. This can only be accomplished through regular testing.
Testing one sample one time will not reflect the state of the coffee program, but only provide a snapshot of the particular sample. The level of testing depends upon the level of quality desired. It is not uncommon for specialty roasters to test every batch produced. The key is to determine a level that reflects the variability of the coffee produced, balanced with cost and practicality. If the systems of manufacture are well organized and the green beans of known good quality, less testing may be indicated. If a new quality control system (or manufacturing system, such as a new roaster) is being put into place, it is best to over-test initially until the level of variability is known. At certain times during the crop year, the green beans can show more variability; at these times more testing is necessary. Clients typically have their products tested monthly, quarterly, and (for those with the highest standards of quality) even weekly.
Testing costs are broken into costs for individual tests and packages of testing. The different forms of coffee (green, roasted, ground) require different methods of testing and consequently have different costs. Coffee Analysts offers discounts for numerous samples received at once (as they can be processed more efficiently) and for ongoing testing programs where an agreed upon number of samples is received weekly or monthly. Typical costs for a standard testing package, including physical and sensorial testing, are determined on an individual basis.
For each sample or set of samples received, a report is written based upon the customer’s inquiries regarding the samples received. This report details the purpose of the test (what one expects to find out), when the sample was received and in what condition (referred to as chain-of-custody), the methods used in testing (including the definition of measurements and instrumentation used), the actual results of testing the samples, and a final conclusion based upon the original purpose. If necessary, background on certain coffee, technical, or testing issues is also provided so that a better interpretation of results and analysis can be made.
If the program of testing is regularly scheduled, after the first report detailing the purpose and methods, only the results of testing will be reported, often along with analysis. After a certain amount of data has been developed, summary reports can be produced looking at samples according to blend, means and/or source of production, or over time to observe trends.
The word “quality” denotes a level of kind or character. In the case of coffee, the simplest classification of coffee quality is between “specialty” (coffee purchased primarily for its flavor with less regard for price) and “commercial” (coffee purchased primarily for its price and availability with less regard for flavor). These products appeal to different groups of individuals (segments) and many levels lie between the two extremes. Profitable coffee sales depend upon meeting the needs of the targeted customer segment. Coffee Analysts categorizes roasted coffee products into 5 classifications (from highest to lowest): Super–specialty, specialty, usual-good-quality, average quality, and commercial quality.
The final quality of flavor of the coffee consists of the nature of the green bean used, the roasting conditions, and freshness of the coffee.
Most simply, it is consistently meeting an established set of standards, including the green beans used, the roasting techniques employed, and packaging for freshness. With coffee, conformance to standards is mainly measured by sensorial analysis.
It is the use of the human sensory system to identify and measure the flavor of foods. While the human sensory system is one of the most sophisticated instruments, its very sensitivity makes it subject to a multitude of interferences, both physical and psychological. A good sensory test must be carefully conducted under controlled conditions using a panel so that several separate sensory systems can evaluate the samples. Coffee professionals refer to the process as “cupping” or “tasting” depending on how the sample is prepared.
Anyone with a working sensory system can perform sensory analysis. However, a trained panel can usually isolate problems and characterize a coffee sample more accurately and easily based upon specific knowledge, training, and experience.
Coffee is vastly complex, capable of producing thousands of chemicals that can be perceived, depending on the origin, roast, and age of the coffee. These various chemicals can enhance each other, cancel each other out, operate independently of one another, or combine to create new perceptions. Great strides have been made in instrumentation, but the simplest, least expensive, and most replicable results are obtained by sensorial analysis in coffee testing.
Physical analysis of green or roasted coffee can unveil further clues as to the quality of the coffee or reveal the source of a problem found during sensory analysis. For example, if a number of defects are found in a green sample, the sample will usually display a number of off-flavors on the cupping table. Physical specifications of green beans (such as bean size, moisture, and defects) to be used in blends determines the level of allowable quality, while physical specifications of roasted samples (such as roast degree and grind particle size) indicate the influences of the manufacturing processes on the coffee.
Chemical analysis is most useful when one wants to quantify a certain known chemical, such as caffeine.
Coffee Analysts is aware of no chemical test that would allow such a conclusion. By the time the bean is separated from the fruit and roasted at temperatures of 400° F or more, any pesticide or fungicide residual is destroyed. The nature of the soil and methods of fertilization used to produce the green bean cannot be determined either.
All staff members are trained coffee scientists and conduct evaluations and analysis under the management of the Director of Coffee Operations. In a sensory test, at least 3 panelists (usually 4), including at least one senior panel leader with more than 15 years of coffee tasting experience, are presented with at least 5 iterations of a sample. Due to the variability of the human sensory system, even the most experienced and well-trained tasters will have irregular sensitivity. The team approach assures that reported sensory results are accurate and reasonably replicable.
The testing methods used are published by the Association of Analytical Chemists (AOAC), the International Organization for Standardization (ISO) or other generally accepted testing organization. The method used is always explained in reports along with the particular publication reference.
Testing methods fall into two general classifications: primary and secondary. A primary testing method is one that directly measures the aspect being tested to a highly accurate degree, while a secondary standard measures other aspects of the sample to conclude a measurement (indirect measurement). For example, the primary testing method for moisture testing of green and roasted coffee is the Karl Fischer titration. This requires elaborate sample preparation, specialized laboratory equipment, and a skilled chemist to perform the test. As a result, the cost of testing by this method is several hundred dollars. While secondary methods may not be as precise, they are almost always of adequate precision for making decisions and more economical for the customer.
To ensure consistency of testing methods, the Director of Coffee Operations maintains a Procedural Manual for Testing that includes a copy of the published method, specific equipment to be used, directions for performing the test, and forms to be used in recording and reporting results.
Coffee Analysts uses both professional laboratory equipment that would be found in any analytical lab such as vacuum ovens and scales, certified whenever possible by a recognized organization (such as the ISO) and specialized equipment to fulfill a particular purpose, as for color measurements. All equipment is regularly calibrated and logs kept of the calibration.
The easiest way is to smell it in the dry state. Stale aromas appear first at this stage. For more information on staling of coffee, check the “packaging” section under “Testing” or the paper “What is Coffee Freshness?”