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Roughness is a good way to control bitterness, because the finer the grinding, the higher the extraction rate, the easier it is to extract high molecular weight bitter substances such as chlorogenic acid, quinic acid, caffeine and carbides. On the contrary, if the grinding is too rough, the lower the extraction rate is, the more difficult it is to extract the astringent bitter substance with high molecular weight, but the sweet taste with middle molecular weight may remain in the coffee grounds because of insufficient extraction, which is a waste. Therefore, baristas should pay attention to whether the thickness of the powder is normal every day. Too thick or too fine will cause abnormal extraction and affect the flavor of coffee.
