The Coffee Scientist’s Guide to Specialty Coffee Beverages


Introduction

Hello Coffee Scientists! Welcome to the Scientist’s Guide to Specialty Coffee Beverages!

This guide will take you through the multiple types of beverages, their ingredients, their chemistries, and draw out expectations that have been formed for them in the years since they’ve been introduced to American shops.

(This guide will be updated over time as I find time to add each beverage! Check back periodically for updates.)


Black Coffee


Probably the most misunderstood beverage due to the fact that most people do not try properly prepared coffee, and write it off as a bitter tasting drink that lacks redeeming flavors. This beverage is the driving force behind third wave coffee.

Some enjoy coffee, but only in specialty beverages where outside chemicals often neutralize the compounds in coffee that bring about all of the wonderful flavors and aromas that might be experienced in an expert-crafted cup. What most do not realize is that coffee has a complex chemistry, and as such the crafting of a proper cup has to take into account precise proportions of coffee and water, as well as the time and means of extraction of compounds.

Chemically speaking, coffee is an aqueous solution (a solution in which the solvent is water) of Hydrocarbons, Alkaloids, Alcohols, Aldehydes, Ketones, Acids and anhydrides, Esters, Lactones, Phenols, Furans, Pyrans, Thiophenes, Pyrroles, Oxazoles, Thiazoles, Pyridines, Pyrazines, Nitrogenous compounds and amines, Sulfurs, Minerals, Carbohydrates, Proteins, Lipids, Phenolic compounds, Waxes, Oils,  Volatile components. As you can tell from this long list, coffee is a very complex solution, and many different chemical factors can contribute to the taste of coffee. Think of yourself as a chemist when creating coffee – what sort of physical and chemical processes can alter the way this solution is created?

 

There are 5 main factors in crafting a great cup: The grind (grain size of grounds – more accurately, the surface area of coffee grounds in contact with water during extraction), the proportion (by weight* ratio of coffee to water), the extraction time (how long the grounds stay exposed to the water), the temperature (how hot the water is), and the water (how fresh and pure the water is).

*An important thing to know is that proper proportion is only accurately achieved by weight, not volume. This is because measuring by weight accounts for a single mass of coffee, while measuring by volume does not. Think about it: the smaller the grain size of coffee you scoop, the more coffee you are scooping, because the void space between grains is reduced.

These factors change based on the roast of the coffee, the method of extraction, and most importantly the desired extraction of chemical and aromatic compounds. Over time, chemical engineers, coffee tasters, and baristas alike have experimented with coffee and have formulated proper proportions for different methods of brewing coffee. Not all coffee shops and/or baristas take into account these factors, though. Many people who have made coffee themselves may not have known about these factors in the first place, and had a bad cup of coffee.

As far as equipment goes, it is important to look at factors related to automatic-home equipment that can affect the taste of your coffee. For example, many automatic home drip-brew systems do not heat your coffee enough for proper extraction, and a lot of the time the coffee burner is left on and burns the solution (this can be fixed by storing the coffee in a good thermally insulated carafe). Many home espresso machines and single-cup brew systems do not have proper pumps to push the water through the coffee grounds properly, leading to bitter or sour shots of espresso and cups of coffee. The reason a lot of this goes under the radar is that many people do not know what coffee is supposed to taste like, because they’ve never had a properly prepared cup of coffee! The lack of affordable, consistent drip systems and espresso machines is why many coffee shops make coffee with manually operated equipment.

How do you know what coffee is supposed to taste like? That’s a hard question, because there are tons of different answers based on the origin of the coffee, the altitude is was grown at, the method of processing of the coffee from cherries into green beans, the roast of the coffee, and the freshness of the coffee!

There are 4 main things you should notice in a cup of coffee: the flavor (what it tastes like), the aroma (what it smells like), the acidity (how acidic versus rich the coffee tastes), and the body (how viscous the coffee feels flowing around your mouth). The flavor is often the hardest of these things to pick out, but that can be helped with a complimentary food pairing! Many baristas and coffee tasters recommend different types of food pairings based on the type (origin/blend) and roast of coffee you are tasting. A great way to pick out flavor notes is to also try two different types of coffee at once, for a relative comparison.

Is coffee supposed to taste bitter? A high-quality coffee, prepared properly should absolutely never taste bitter. The grain size, proportion, and temperature are often to blame for this: too small a grain size, and too much compounds are extracted creating a strong, bitter taste – meanwhile, if the grain size is too big not enough compounds will be extracted and the coffee will taste sour. Temperature can also affect how rapidly and what types of compounds are extracted, and high temperatures can often lead to the scalding of coffee grounds, creating a burnt taste.

So what types of flavors are found in coffee? A great representation of the flavor notes found in coffee have been compiled by The Specialty Coffee Association (SCAA) and World Coffee Research (WCR) in the coffee taster’s flavor wheel:

flavor-wheel-en

For descriptions of coffee flavor notes, the best reference I have found is WCR’s Sensory Lexicon, which can be found here.

Wondering how origin influences the flavor profile? Different regions have differing altitudes, and differing soils that contain different chemicals that influence the growth of coffee in certain ways. Different regions also contain different subspecies of coffee, which contain differing amounts of chemical compounds. Coffees that are single origin will have very specific and notable flavors. Coffees that are blends of several origins will have a mix of those flavors, and can make for a more complex cup. If you are starting out with coffee tasting, I recommend trying single origin coffees. If you are looking for a complex cup, on the other hand, look for unique blends!

Here is a map of some different growing regions, and their associated flavor profiles:

The-Coffee-Map1_grande

This is sourced from here.

Freshness is another factor that can cause a lack of flavor. Coffee, when exposed to air, can become stale. This is why is is best to only grind coffee when you are about to start brewing. This is because ground coffee has a higher surface area, which leads to quicker oxidation. The four main factors that affect freshness are air, heat, moisture, and light. Coffee should be vacuum sealed, and kept in a dry, opaque container at room temperature. even stored properly, coffee is only good for up to 2 weeks after being roasted. This date can be extended with more advanced, costly vacuum sealing techniques – but only so much. As the compounds in coffee are destroyed by the air, heat, moisture, and light, the coffee will start to lose flavor and aroma. This is the exact reason why many third wave shops prefer to roast their coffee in house. Not only can they control the freshness and amount of coffee roasted, but the roast of the coffee itself.

How does roast affect flavor? I’ll create a more detailed guide on temperature and roasting in the future, but for now, here is a well presented infographic from the National Coffee Association (NCA):

roasting-infographic-small.png

Another factor that is often overlooked is the plating of the coffee. It has been proving that the plating of the coffee can alter the way we perceive the taste of the beverage. In The Perfect Meal: The Multisensory Science of Food and Dining, Spence and psychologist Betina Piqueras-Fiszman from Wageningen University in the Netherlands show us that the most minute changes in the presentation of our food can alter our taste palate. The same goes for coffee! This has led to a whole industry based around coffee mugs, dishes, and cups, among other things. It has also led to the popularity of latte art among baristas: professional quality latte art can lead us to perceive the drink as tasting better. Something to keep in mind, not only for black coffee, but all specialty coffee beverages!