Why does illy coffee bean taste bitter after hand washing?

According to your description, it should not be a problem of brewing. For coffee taste, the proportion of extraction is less than 1%. Among them, 5% are raw beans, 4% are baked, and 1% are cooked with equipment or utensils. If top-level equipment is considered, such as variable pressure and temperature control equipment, the proportion of raw beans is also the highest, with raw beans 4%, baking 3%, equipment 2% and brewing method 1%.