Coffee is one of life’s great pleasures. The preparation and consumption of the perfect cup of coffee is an essential ritual for millions of people around the world. But great coffee does not happen without care and attention at every stage of preparation. `From bean to cup’ may be a clichéd expression, but it really captures the essence of how perfect coffee is made. Everyone in the chain, from farmer to consumer, needs to understand the essentials of achieving that perfection.
Coffee is an agricultural commodity grown in over 100 countries around the world. Guaranteeing the supply of good quality coffee that goes to make our morning cuppa is a complex undertaking. Different origins have unique flavour profiles. Harvests vary around the globe, and coffee quality also varies within each harvest. Therefore, ensuring a consistent flavour profile for any coffee must take account of the availability of green coffees with the right quality and price. To maximise the value of their crop, farmers need to treat their harvest to maintain quality and avoid damage caused by incorrect storage and handling. Advice from agronomists and agricultural outreach scientists helps to develop the skills and expertise farmers need.
Once green coffee reaches consuming countries, it is processed into a wide range of products. The major applications are roast and ground coffee, soluble coffee and, increasingly, pods for on-demand coffee machines. Green coffee may be roasted and ground differently for each application. Increasingly sophisticated technology is applied in coffee processing, including cryogrinding (of roast coffee) and freeze-drying (of soluble coffee). The main method currently used to assess the quality of coffee (green or roasted) is cupping. This relies on the expertise of a handful of expert tasters, whose job it is to maintain the flavour integrity of a wide range of products. Development of new products as well as ensuring the consistency of existing blends therefore relies on a few expert individuals. The development of this expertise takes time as well as a sensitive palate. The accuracy of sensory assessment depends on the health of the assessor, and can suffer from subjectivity.
Analysis of coffee sample is carried out using gas chromatography and quadrupole time-of flight-mass spectrometry (GC/QToF) analysis of coffee samples.
New developments in aroma analysis technology mean that it is now cost-effective to deploy sophisticated aroma analysis to a range of foods and beverages, including coffee. In fact, coffee is a very good candidate for this type of analysis because approximately 40 aroma compounds describe the flavour of coffee as experienced by a sensory assessor. By analysing a set of coffees using this approach, it is possible to describe each coffee by its unique aroma chemistry ‘fingerprint’. The effect of different roasting conditions can be tracked chemically and linked to effects on flavour. Similarly, the effects of origin, harvest and storage can be chemically identified. What emerges quickly is a powerful tool to manage the quality of coffee products.
Statistical mapping of coffee aroma ‘fingerprints’ using Principal Components Analysis. This clearly demonstrates the separation of coffee types using aroma components. Each sample is a different origin and the diagram is a 2D representation of a 3D map.
Red: Brazilian Roast
Green: Java Sumatra Roast
Brown: Costa Rican Roast
Blue: Colombian Supremo Roast
Grey: Espresso Roast
A major application of aroma fingerprinting is in developing and cost-optimising blended products. The benchmark product can be defined by its aroma fingerprint, which is an objective measure of its flavour profile. The fingerprint can be fixed, so that any subsequent blend is compared against this fixed reference, which does not vary with time or rely on the state of a sensory assessor. So suppose I need to reformulate my blend due to the availability of green coffee. I now have a fixed fingerprint to match. By fingerprinting the individual origins I have available, I can then use statistical analysis to identify the blends with potential to best match my target aroma fingerprint, all without having to taste a single cup of coffee. Additionally, I could overlay price information, so that I can then ask the question ‘which blend of origins best matches my flavour target at least cost?’ Once I have a small number of candidate blends, I can cup them and decide which best meets my needs. Another very powerful application for aroma fingerprinting is matching existing blends. Suppose I am asked to match the flavour of Blend X. I can use a trial-and-error approach to blending and cupping, and hope I hit upon something close. Or I can use the aroma fingerprint of Blend X to help identify combinations of origins that match the target, and then cup the best of these.
I should state clearly that aroma fingerprinting does not replace the need for cupping, but instead provides objective data to support sourcing and blending decisions. Availability and costs can also be factored into the analysis so that a comprehensive model for product management can be developed. It will make blend development and management more efficient, and avoid some of the pitfalls inherent in relying completely on expert cupping.
To discuss this work or any other coffee-related science in more detail, please contact Simon Penson firstname.lastname@example.org
Dr. Simon Penson, Head of Cereals & Ingredients Processing, Campden BRI
Dr. Julian South, Head of Chemistry & Biochemistry, Campden BRI
Campden BRI (www.campdenbri.co.uk) provides technical, legislative and scientific support and research to the food and drinks industry worldwide. We offer a comprehensive “farm to fork” range of services. Our members and clients benefit from industry-leading facilities for analysis, product and process development, and sensory and consumer studies, which include a specialist brewing and wine division.