Maximizing the flavor and aroma of your brewed coffee

Brewing great tasting coffee requires a keen focus on detail. With so many variables influencing how coffee tastes, it is important to make sure quality protocols are employed not only throughout the whole brewing process, but following it as well. While your cafe may be using the best coffee possible, dialing in your recipes, and producing great tasting coffee right after brewing; your customers may still experience a cup of inferior tasting coffee when they are served. This is due to a small detail many overlook: the storage of coffee after it is brewed. 

Many cafes use insulated air pots, which are a great way to store coffee while also keeping it hot. However, storing brewed coffee in air pots or similar vessels for too long can actually cause coffee to taste overly sour, and lacking complexity and balance. This is for two reasons: the breakdown of chlorogenic acids and the loss of volatile aromatic compounds. 

Chlorogenic Acids (CGAs) are found in coffee at all stages. From a seed inside of the coffee cherry where it makes up 10% of the coffee's weight, to processing, roasting and brewing where there can be anywhere from 15-325 mg per cup of coffee, CGAs are always present. The particular CGA we are talking about when it comes to the quality of flavor in coffee is caffeoylquinic acid. It is a compound composed of harsher-tasting quinic and caffeic acids. During roasting, the amount of decomposition of CGAs primarily depends on roast level, meaning that the darker the roast, the more CGAs are broken down, and the more bitter coffee tastes due to the amount of quinic acid present.

When it comes to holding CGAs stable in brewed coffee, 175-185°F is the ideal range, outside of which both CGAs and Quinic acids become unstable and contribute to sour, harsh flavors. This occurrence is further proven by measurable pH decreasing while titratable acidity increases with quinic acid being the contributing factor for 25% of those changes.

Another factor that influences the quality of brewed coffee over time is the loss of aromatic volatile compounds. These compounds are what we smell when grinding or brewing as they evaporate at low temperatures. This becomes consequential when coffee is stored for too long without enough head space in the air pot. Head space is the amount of room between the brewed coffee and the top of the container it is stored in. With volatile compounds evaporating into and being lost in this space for too long, the coffee your customer receives will be lacking those aromatic qualities that were enjoyable when the coffee was first brewed. The ideal coffee storage vessel will be filled to its full capacity and emptied within an hour to limit quality lost to excess head space.

The take away from our newfound knowledge of CGAs and volatile aromatic compounds is this: storing coffee for any more than an hour is no good. Coffee stored for too long is lacking aromatic complexity and is overly harsh and sour tasting. If two customers order a cup of coffee from the same pot, but an hour apart from each other, they are drinking two different coffees. The one brewed at the top of the hour is richly aromatic and balanced in flavor, while the later cup will be lacking in complexity and balance. For this reason, we at Speedwell highly recommend that your brewing protocols include a closely watched time limit of no more than an hour for stored brewed coffee. Let’s keep our coffee fresh and our customers happy :) 

References, Sources, and Studies

• Balzer, H.H. Coffee: Recent Developments, Blackwell Science, Oxford, 2001, pp. 18–32. 
• Illy, Andrea, and Rinantonio Viani. Espresso Coffee: The Science of Quality. Elsevier Academic, 2005.
• Lingle, Ted R. The Coffee Brewing Handbook: A Systematic Guide to Coffee Preparation. Specialty Coffee Association of America, 2011.