The sour, mellow and bitter taste of coffee is caused by complex chemical changes in roasting.

The color, aroma and taste of coffee are caused by some complex chemical changes that take place during the baking process. So raw coffee beans must go through a proper chemical process to achieve the most balanced state of its essential ingredients in order to be regarded as the best baked beans. The aroma of coffee changes with the heat, so the baking time should be shortened as much as possible, and the heat should be controlled at the lowest temperature that can produce effective chemical composition of coffee beans, that is, the time and heat of the shortest process, so that coffee beans can produce the most suitable composition ratio.

The sour taste must be affected by the quality and variety of raw beans. As far as the elevation of the variety is concerned, coffee grown in highlands is sour than that in lowlands, and beans just harvested are sour than beans that have been harvested for a while. The increase and decrease of acid varies with different kinds of acid. generally, the beans with shallow baking are rich in sour taste, and those with deeper baking degree are lack of sour taste. Just harvested beans, good quality, high moisture content, if the appropriate heat to produce a moderate sour taste, will make the coffee taste better, make people feel more deep.

Generally speaking, we use strong alcohol to show the round, mellow and strong taste of coffee. The unique sweetness of high-end coffee is related to the bitterness, so the refreshing taste must have a sweet taste. In the baking process, some carbohydrates such as sucrose and glucose will be caramelized, and the rest will form sweetness. the product of moderate sweetness is easily lost if it is overheated in the process of baking and brewing.