Where does the coffee aroma come from? How does coffee taste sweet and sour?

Roasting is one of the most attractive aspects of the coffee industry. Green coffee beans have almost no flavor at all, taste will have a rather unpleasant vegetable flavor, but after roasting, it will transform into an incredibly aromatic and complex coffee beans. The smell of freshly roasted coffee beans is refreshing and delicious. Fast or slow? Shallow or deep? jianyan