為何咖啡烘焙愈深、油脂感愈好？油哪裏來的？ Why Does Coffee Have Better Crema with Dark Roasting and Where Does the Oil Come from?
The appearance of oil on the surface of coffee beans occurs during the roasting process when lipids within the fibrous structure migrate to the surface. The oil on the surface of coffee beans carries essential flavor compounds and significantly influences the mouthfeel of brewed coffee. But is coffee oil good or bad?
Coffee green beans contain proteins, sucrose, minerals, chlorogenic acids, cellulose, water, and lipids. During roasting, each of these substances undergoes different reactions due to the applied heat, leading to a series of changes. These changes include well-known processes like the Maillard reaction and caramelization. Another crucial change during roasting is the formation of oil on the surface of coffee beans.
The formation of oil on coffee beans' surface is a result of the breakdown of the internal structure due to heat, making the beans porous. As the beans roast, the generated carbon dioxide pushes the lipids to the surface. The longer the roasting time, the more oil emerges as the internal structures of the beans decompose further. Deeper roasted coffee beans weigh less and contain more oil.
The oil released after roasting is the residual carbon dioxide being pushed out, which also brings the oil to the surface. Within the first month after roasting, coffee beans continue to release carbon dioxide, with a particularly high rate in the first few days after roasting. This is why lightly roasted coffee can also develop an oily surface after extended storage, and depending on the bean's hardness, the oil slowly floats to the surface.
Coffee oil adds a full and rich mouthfeel to the brewed coffee, providing a creamy and thick sensation. Hence, choosing deeper-roasted coffee can enhance the crema, even though deeply roasted coffees may lack the complex floral and fruity aromas found in lighter roasts, they offer a distinctive mellowness in mouthfeel. This is especially important when brewing espresso with an espresso machine, where coffee oil plays a crucial role.
In general, Arabica green beans contain around 15% lipids, whereas Robusta green beans contain around 10% lipids. So, why do traditional Italian espresso blends use Robusta beans? There is a misconception that Robusta beans produce a thicker crema (the concentrated coffee oil) compared to Arabica beans, when in fact, Robusta beans have less oil. This is because Robusta beans grown at lower altitudes have lower density and thus easily release oil during roasting. Additionally, Robusta beans are cheaper, making them more favorable for traditional Italian espresso blends. For high-quality Italian espresso blends, Arabica beans should be used for their higher lipid content, greater sweetness, and diverse flavor compounds.
有時候深焙會過分強化咖啡的特性，但需要有能夠承受深焙的生豆品質，否則只能品嚐到烘焙的味道。Tim Wendelboe曾說過，2004年世界咖啡師(World Barista Cup, WBC)冠軍，「無論是否深烘，88分的咖啡通常會比84分的咖啡味道更好。即使烤得很黑，高品質材料的味道仍然會比低品質材料好一點。」JC咖啡的義式配方是用高品質的阿拉比卡豆，風味豐富、口感厚實濃稠。
Sometimes, overemphasizing roasting can overpower the coffee's inherent qualities, but it requires high-quality beans that can withstand the deeper roasting. Tim Wendelboe, the winner of the 2004 World Barista Cup (WBC), once said, "Regardless of whether it's deeply roasted, an 88-point coffee usually tastes better than an 84-point coffee. Even if roasted very dark, the flavor of high-quality beans will still be slightly better than low-quality beans." Justin Coffee's Italian espresso blend is made with high-quality Arabica beans, offering a rich and robust flavor with a full-bodied and mellow mouthfeel.
While coffee oil contributes to a full-bodied mouthfeel, it also brings oxidation issues. After roasting, coffee beans are exposed to oxygen in the surrounding air, and the contact between the beans' surface oil and oxygen leads to the formation of peroxides, resulting in undesirable acidic and off-flavors. This means that deep roasted coffee should be consumed earlier after roasting compared to lighter roasts to limit the impact of oxidation.
If our preference is for a rich and robust coffee, then a deep-roasted coffee with abundant oil is the right choice. For those seeking a delicate and light coffee, a lightly roasted coffee with floral and fruity aromas is ideal. And for those desiring a smooth and balanced coffee, a medium-roasted coffee with subtle fruit and nutty notes is an excellent option. Experimenting with different coffee flavors allows us to explore intriguing sensory experiences!
✔ 堅持新鮮烘焙 ✔ 堅持篩豆 再烘焙 ✔ 堅持使用莊園咖啡
➤ CQI Q Grader咖啡品質鑑定師，親自杯測品鑑，為您把關每一杯咖啡
➤ 單一莊園咖啡 具風味、層次佳
✔ Stick to fresh roasting ✔ Stick to sieving and roasting ✔ Stick to estate coffee
➤ Professional roasting brings out the diverse and rich personality of coffee
➤ CQI Q Grader coffee quality appraisers, personally cupping and evaluate, check every cup of coffee for you
➤ Single-origin coffee with good flavor and structures