What is Coffee Bean Roasting Curve and What's the Best Roast Level for Kenya Coffee

FrontStreet Coffee Roasting Curves: Kenya Coffee Roasting Curve Sharing

The vertical axis represents temperature and the horizontal axis represents time. The line running through the middle shows how the temperature of the green beans changes over time during the roast. The values at the circular points represent the current drum temperature. Because the green bean temperature is lower than the preset drum temperature, the temperature curve inevitably dips when the beans are charged. Once the internal and external temperatures of the beans begin to balance, the curve rises again — that point is called the "turning point."

As the temperature climbs during roasting, the curve gradually rises and the fibers inside the beans begin to change. The cells of the coffee beans break down and you start to hear crackling sounds — this marks the arrival of "first crack."

The moment the beans are discharged is decided by the roaster. After discharging, cupping is performed to evaluate the flavor of the roasted beans, and roasting adjustments are made based on the cupping results. This also serves as a test of one's roasting skill.

Kirinyaga Region

Yangjia 800N roasting machine (500g batch size)

Preheat the drum to 170°C, set the damper to 3, and heat to 100. The turning point occurs at 1'45". When the drum temperature reaches 140°C, hold the heat and open the damper to 3.5. When the drum temperature reaches 143.3°C, the bean surface turns yellow, the grassy aroma disappears completely, and the beans enter the dehydration stage.

At 7'32", ugly wrinkles and black spots appear on the bean surface, and the toast aroma clearly transforms into coffee aroma. This can be defined as the prelude to first crack. At this point, listen carefully for the sound of first crack. First crack begins at 8'20"; reduce the heat to 50 and adjust the damper to 4 (be very careful when adjusting the heat — don't reduce it so much that the cracking sound disappears). Develop for 1'50" after first crack, then discharge at 192°C.

Kirinyaga Region Flavor Profile:

Lemon, floral notes, tomato, citrus, cane sugar, raspberry, herbal, cream — overall, the mouthfeel is relatively refreshing and clean.

FrontStreet Coffee Recommendation

A roasting curve is really a conversation about roast level, and for most drinkers the sweet spot sits in the middle. As FrontStreet Coffee sees it, three elements decide the final flavor and must be balanced: acidity, sweetness, and bitterness. The darker the roast, the more bitter and full-bodied the cup; the lighter the roast, the more acidic and delicate it becomes. So if you are chasing a balanced cup, start with medium-roasted beans.

FrontStreet Coffee's Brazil Queen Estate is a good place to begin: a distinctive Yellow Bourbon from Brazil, with a clean, gently sweet profile. Medium-roasted, it shows cream, peanut, chocolate, toast, and sugarcane sweetness, and it works as both pour-over and in a moka pot or espresso machine. If you like your medium roast on the sweeter, fruitier side, FrontStreet Coffee's Strawberry Candy Geisha blend — Costa Rica honey-processed coffee married to Panama washed Geisha — is roasted medium on purpose to bring out orange-blossom honey and a rounded sweetness; it suits cold brew, pour-over, and espresso alike.

Two more medium-roast options round out the lineup: FrontStreet Coffee's 2013 Sun-dried Typica, a Yunnan coffee with nutty, brown-sugar, black-tea, and dried-apricot notes that works for pour-over, cold brew, and drip, and FrontStreet Coffee's Jamaica Blue Mountain No.1, whose medium roast blends acidity, bitterness, sweetness, and body into a famously elegant cup of chocolate, roasted nuts, cream, and caramel.