[Illustrated] What Details Should You Pay Attention to When Roasting Coffee for Sweetness? The Roast Level of Coffee Beans and Their Characteristics

In the previous lesson, we learned about the impact of the development phase on coffee flavor during coffee roasting. The longer the development time, the deeper the roast level of the coffee. In this lesson, we will explore what role the intermediate phase plays throughout the entire roasting process.

Reviewing the Intermediate Phase

The intermediate phase is the period from the yellowing point to the beginning of first crack. During this time, coffee beans transform from yellow to brown or light brown, the beans begin to release steam and expand, and pleasant aromas such as roasted corn and toasted bread are released through the Maillard reaction.

During the intermediate phase, the expansion of coffee beans causes a significant amount of silver skin attached to them to fall off. At the same time, smoke is produced, so it's necessary to open the damper appropriately during this stage to extract smoke and silver skin. If the damper is too small during this phase, it may result in a smoky flavor in the coffee beans.

The Intermediate Phase is Key to Developing Coffee's Sweetness

Coffee changes from green to yellow during dehydration. As heating continues, browning begins. The Maillard reaction causes sugar substances within the coffee beans to start converting into aromatic compounds and acids. When the roasting temperature reaches 171°C, the coffee beans turn brown, and caramelization reaction begins. Since caramelization breaks down sugar substances, the Maillard reaction during this period (171°C to before first crack) becomes slower. The caramelization and Maillard reactions during this period will produce flavors such as fruit, sucrose (sugars), and others in the coffee.

Alright, I believe everyone is getting confused by terms like "Maillard" and "caramelization," so FrontStreet Coffee will use a simple roasting experiment to illustrate.

Using FrontStreet Coffee's roasted Brazil Red Bourbon as an example, demonstrated with a Yangjia 800N semi-direct fire roaster, this coffee bean has an inlet temperature of 155°C, turns yellow at 7 minutes (153°C), which means entering the intermediate phase, while first crack begins at approximately 181-183°C. During this period, we conducted four different operations respectively: ① Slightly increase heat, increase temperature rise rate, shorten the intermediate phase; ② Keep heat unchanged; ③ Slightly reduce heat, extend the intermediate phase; ④ Significantly reduce heat, extend the intermediate phase.

The development time after first crack and the drop temperature remain unchanged.

The actual roasting results and flavor feedback are as follows:

① Yellowing point at 7'00 (152.8°C), first crack start at 9'02 (184°C), intermediate phase duration 2'02.

Flavor feedback: Flat flavor, slight fruit acidity, peanut skin, almond

② Yellowing point at 7'03 (153.2°C), first crack start at 9'30 (183°C), intermediate phase duration 2'27.

Flavor feedback: Nuts, sucrose, slight fruit acidity, chocolate

③ Yellowing point at 7'08 (153.4°C), first crack start at 10'09 (183°C), intermediate phase duration 3'01.

Flavor feedback: Nuts, caramel, chocolate, noticeable sweetness

④ Yellowing point at 6'55 (153°C), first crack start at 10'45 (181.5°C), intermediate phase duration 3'50.

Flavor feedback: Nuts, sunflower seeds, dark chocolate, burnt bitterness

This roasting comparison shows that when the intermediate phase for Brazil Red Bourbon coffee beans is too short, the caramelization reaction time is insufficient, resulting in flat and dull flavors. If the intermediate phase is too long, the caramelization reaction becomes excessive, producing burnt bitterness. For this particular bean, controlling the intermediate phase to about 3 minutes allows both overall flavor and sweetness to be fully expressed.

[Key Point] Properly extending the intermediate phase can enhance the sweetness of coffee beans.

So, are all coffee beans suitable for extending the intermediate phase to increase coffee sweetness? Let's review the process of the intermediate phase once more.

[When coffee beans reach about 151-157°C, they turn yellow and immediately begin to expand and undergo the Maillard reaction, causing sugar substances within the coffee beans to start converting into aromatic compounds and acids. When the roasting temperature reaches 171°C, the coffee beans turn brown, and the caramelization reaction begins, producing caramel-like substances.]

In other words, the longer the time between 171°C and before first crack, the more prominent the caramel and nutty characteristics will be.

For Yirgacheffe coffee beans, which are full of floral and fruity aromas, although developing the intermediate phase to 3 minutes will express sugar substances and noticeable sweetness, it will diminish the pleasant citrus acidity and will likely be accompanied by a nutty bitter finish. When the intermediate phase is controlled to about 2 minutes and 30 seconds, the acidity and sweetness of Yirgacheffe blend well together, expressing a delicious sweet and sour taste.

[Key Point] When roasting coffee, during the intermediate phase, ensure the damper is opened wide for smoke extraction and silver skin removal. There is no optimal duration for the intermediate phase; it depends on how you want to express this particular bean. Properly extending the intermediate phase can enhance coffee sweetness. However, to highlight the excellent acidity of coffee, you need to control the duration of the intermediate phase and shorten the caramelization reaction time.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473