Explanation on the baking stage of roasted coffee beans

the roasting of the coffee beans in

Coffee is loved by people, the key lies in the aroma formed after roasting and the taste when drinking, because the coffee beans themselves do not have any special taste. "Baking" is to change and reorganize the internal substances of raw beans to form a new structure, and to become a favorite drink with strong and mellow flavor.

Roasting coffee is a pyrolysis that changes the substances inside the green beans, producing new compounds and recombining them to form aromas and alcohol flavors. This effect only occurs at high temperatures, and if only low temperatures are used, they cannot cause decomposition, no matter how long the roast takes.

Most people think that baking is nothing, just frying raw beans with fire. In fact, roasting is the most difficult step in coffee processing, and it is both a science and an art. In the West, experienced bakers enjoy a high status.

Baking can be roughly divided into three stages:

drying

At the beginning of baking, green beans begin to absorb heat and gradually evaporate the water inside. At this time, the color gradually changed from green to yellow or light brown, the silver film began to fall off, and a faint grass fragrance could be smelled. The main function of this stage is to remove moisture, which accounts for about half of the baking time. Since water is a good conductor of heat, it helps to roast the internal substances of coffee beans. Therefore, although the goal is to remove water, but the roaster will make good use of the temperature of the water, and properly control it, so that it does not evaporate too fast, usually the best control of water in ten minutes to reach the boiling point, at this time, the internal substances are fully heated, the water also begins to evaporate, spilling to the outside of the coffee beans.

pyrolysis

Bake to about 160 degrees Celsius, and the water in the beans evaporates into gas. At this time, the interior of the raw bean changes from endothermic to exothermic, and the first crack occurs. After the crack, it turns to heat absorption, and at this time, the pressure inside the coffee bean is extremely high, reaching 25 atmospheres. The heat and pressure begin to deconstruct the original tissue, forming new compounds that make coffee taste and taste; at about 190 degrees Celsius, the endothermic and exothermic transitions occur again. Pyrolysis continues and coffee beans turn brown to dark brown.

cooling

Coffee must be cooled immediately after roasting to quickly stop pyrolysis and lock in flavor. Otherwise, the high temperature in the beans will continue to take place and will burn off the aromatic substances. There are two cooling methods: air cooling and water cooling. Air-cooling is the rapid cooling of coffee beans in three to five minutes with large amounts of cold air. In the field of professional roasting, large roasters are equipped with a tray with a rotatable push arm; when roasting is complete, the beans are automatically fed into the tray, and the fan at the bottom of the tray is immediately activated to blow cold air, and the coffee beans are stirred by the push arm to cool them. Air-cooled coffee is slow, but clean and non-polluting, and can retain the aroma of coffee. It is used by coffee professionals. Water-cooled coffee beans are sprayed with a layer of water mist on the surface, causing the temperature to drop rapidly. Because the amount of water sprayed is important, it requires precise calculation and control, and it increases the weight of baked beans, which is generally used for large commercial baking.

Coffee beans can be divided into six categories of roasting degree

Light Roasts, Cinnamon, Half City, New England. This roasting is used only for absolutely high quality, fine or upland grown Arabica coffee beans, mainly for the identification and tasting of coffee beans, and generally not for sale in the finished product. Cinnamon, so called because it resembles cinnamon when roasted, produces coffee beans with a lot of acidity but little alcohol.

Medium Light Roasts: Light American, Light City, West Coast.

Medium Roasts, including American Roasts, Breakfast Roasts, Brown Roasts. American roasts are also called "normal" or "brown", which are darker when they are not oily and are generally used for drip coffee roasts.

Medium-Dark to Dark Roasts, Full City, Light French, Viennese. Viennese, meaning slightly darker than a medium roast. This baking will have dark brown spots and a bit of oil on the surface.

Dark/High Roasts: Afer Dinner, Continental, European, French, Italian, New Orleans. Continental can also be called "double roast" or "high roast", which roasts coffee beans with a chocolate-like color and is described as "very dark" or "very important"; Italian, which is mainly used for roasting Italian coffee beans. In the United States, this roast is darker in color and is sometimes referred to as an "espresso" roast, which produces coffee beans that are almost black and very oily, with the predominant flavor coming from the roast rather than the coffee.

Very Dark Roasts, Dark French and Charcoal, of which Charcoal is rarely used. (Origin of carbon-burning coffee: Japan is a country that does not produce coffee and accepts coffee relatively late. Japanese people want to make coffee their own characteristics, so they roast coffee beans to a very deep degree, similar to carbon, named carbon-burning)