There are wrinkles on the surface of coffee beans. Are they defective beans? The reason for the oil on the surface of coffee beans?

"Why is the surface of coffee beans crumpled? are they bad beans?" "the coffee beans are all oiled. How long have you been keeping them?" This is also the question that many guests have about coffee beans! Qianjie Coffee will answer your questions through this article.

Why do coffee beans wrinkle?

People's impression of coffee beans should be smooth, and the appearance of crumpled wrinkles may be deeply puzzling. The wrinkling of coffee beans is a normal phenomenon, which is mainly formed by the quality of raw beans and roasting.

Coffee beans at high altitude are prone to wrinkles.

Generally speaking, the density of coffee beans at high altitude will be higher, and the heat transfer to the bean core will be slower during roasting, that is, the dehydration time will be longer. During endothermic dehydration, the bean body shrinks to form a texture, but because of its high density and close fiber structure, the coffee bean will not expand so that the texture will stretch, so it will show a wrinkled state.

Baking also affects the appearance of folds.

In general, the wrinkling feeling of coffee beans is mostly medium-and shallow-roasted, while the surface of medium-and deep-roasted coffee beans is smooth. Relatively shallow baking degree or long baking time are likely to make the wrinkle texture of the bean surface clear, while if the degree of baking is deep or the firepower is increased, the grain stretching effect of the bean surface will be very good, even seemingly smooth.

However, whether the coffee bean surface has wrinkles or not does not affect the flavor of coffee beans. Wrinkled beans are not defective beans, on the contrary, some wrinkled and ugly coffee beans can show a clean and fresh flavor.

Why do coffee beans produce oil?

Many people think that the oil from the coffee beans means that the coffee is not fresh, which is actually taken out of context. If you are lucky enough to go to a Japanese coffee shop, you can't ignore the shiny coffee beans on the jar. The "oil" on the surface of the coffee beans is actually the fat of the beans. Because the carbon dioxide produced during baking can let the fat in the coffee beans infiltrate to the surface of the beans, which forms the phenomenon of coffee beans coming out of oil.

Generally speaking, the surface oil of beans will be reflected in the deep-roasted coffee, and the deep-roasted coffee beans will show a slight glossy appearance after baking, and a large amount of oil will begin to appear on the surface from the first day to the second day, and the aroma is a good smell such as caramel cocoa cream. If the coffee beans are not fresh, the aroma is greasy, tar, woody smell.

Not only will grease seep out during deep baking, but it will also seep out for a period of time after baking, because the carbon dioxide remaining in coffee beans is still released. This is more common in medium roasting or light roasting, which is dry just after baking and exudates dotted oil with large amounts of carbon dioxide emissions about a week after baking. These dotted oils represent the best taste period for coffee, and the argument that the oil from coffee beans is not fresh is also self-defeating.

Then the main manifestation of the stale coffee is the exhaust of the gas from the coffee beans, accompanied by the loss of flavor substances. The actual judgment shows that when there is stuffy steaming, the powder layer does not have any expansion state, the taste is empty, with the taste of wood fiber. Whether the coffee bean surface is oily or not is not necessarily related to the freshness of the coffee bean.