What is the relationship between the oil yield of roasted coffee beans and freshness?

Should we buy coffee beans that have "oil" or "no oil" in appearance?

Have you ever seen oily coffee beans? Why do some coffee beans have a shiny surface, while others are "dry and comfortable" without greasy? What does the "oil" of coffee beans have to do with freshness? Should we buy coffee beans that are "oily" or "unoiled" in appearance?

Coffee oil that is not oil.

These "oils" scattered evenly on the surface of coffee beans are actually not "oils", but water-soluble organic substances that look like oils. "Coffee oil" itself contains many aroma ingredients of coffee, which can be dissolved in water, so the surface of your brewed coffee will not be covered with greasy oil.

There are two reasons for "oily beans".

There are two reasons for "oily beans". A) stale shallow baked beans b) fresh deep baked beans. The following in-depth discussion.

A) stale shallow baked beans

The light roasted beans, which are light in heat and light brown in appearance, are dry and will not produce oil after baking. About five days after it comes out of the oven (it may be shortened to one or two days at the height of summer), the phenomenon of "spot oil" begins to appear (dotted oil droplets appear on one side of the coffee bean) Please note: a little "spot oil" does not mean it is not fresh. sometimes the flavor of light-roasted coffee beans is at its peak. Continue to put, more than two kilos out of the oven, the surface of shallow baked beans gradually covered with a uniform, thin and bright oil, the smell is not sweet, but with fuel consumption, at this time, the flavor of "shallow baked beans" has gone downhill and should be avoided.

B) fresh deep baked beans

The deep-baked beans with dark brown appearance show a slight glossy appearance after baking, and a large amount of oil begins to appear on the surface from the first day to the second day. The bright-looking "deep-baked beans" not only do not mean that they are not fresh, on the contrary, the deep-baked beans will gradually dry out after being baked for three years, and eventually become dry-looking off-flavoured beans. Therefore, if you see coffee beans that are dry but dark brown in appearance, please pay special attention to whether they are marked with a baking date and are most likely to be stale beans that have gone bad.

The method of judging the freshness of coffee beans

Even if the "shallow baked beans", which are no longer fresh and oily, will gradually dry out after a long time (such as three months), and finally return to the dry and unoily appearance. Thus it can be seen that the appearance of oil is only a reference to judge the freshness of coffee beans, not absolutely.

How should we judge the freshness of coffee beans?

First of all, please choose from the professional coffee roasters who have clearly marked date, brand reputation and emphasize fresh roasting. In addition, excellent coffee bags are usually designed with a "one-way exhaust valve" (a button-shaped hole in the top of the coffee bag) for coffee beans to release naturally occurring carbon dioxide. Point the one-way exhaust valve at the nose, gently squeeze the coffee bag and smell the gas. If it is a charming and fragrant coffee aroma, the freshness will not be a problem. On the contrary, if it does not smell strong enough, or even smells of smelly oil, it means that this bag of coffee has already gone bad and should be avoided.

-conclusion-

"the appearance of freshly baked shallow baked beans should be dry and oil-free, and the surface of freshly baked deep baked beans should be shiny" is the correct concept that we should understand. When buying coffee beans, the appearance of oil, no oil is a reference index to judge the freshness, but not absolutely. It is the best policy to choose reputable merchants and buy them with wide eyes.