How is the wonderful and compound aroma of coffee produced?

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In the process of brewing coffee, we all look forward to the moving moment full of fragrance:

Caramel, flowers, berries, nuts, honey, tea. Wait for all kinds of wonderful and compound aromas

It's definitely the most charming thing about coffee.

SCAA Poster Coffee Tasters Flavor Wheel

More than 300 aroma compounds can be detected in raw coffee beans, and more than 850 in ripe coffee beans, with an astonishing complexity (this data is quoted from boutique coffee science)

But in the process of baking or cooking, there will still be a bad strange smell, which is of course abhorrent.

It is necessary to select high-quality raw beans, filter defective beans and adjust appropriate cooking variables in order to keep the aroma beautiful and flash off the strange taste.

And understanding is the first step in preventing and finding a solution.

Therefore, the seniors shared a translation article explaining the causes of the strange smell of coffee for your reference.

Although it is not a very new article, but there is still a solid practical experience in the generation of strange smells (and written by celebrities)

You can still take a serious look, and compare the hands of Doudou, to find out the problem!

Another article is quoted from the blog of Kuka Coffee, but Kuka should not be the original translator, and the seniors can't find it. In order to be loyal to the original translator, all of the following contents remain unchanged. If some translations are not in line with your experience, please look at English for comparison.

The picture is made by yourself, so that everyone can look at it and imagine it.

The five stages of coffee aroma change

This article is mainly translated from the third edition of "The Coffee Cuppers' Handbook" published by SCAA, Chapter 2

The corruption and defects of the fragrance. Author: Ted R. Lingle

The aroma of coffee is the main purpose for us to buy and drink coffee.

Perhaps some people drink coffee to enjoy the strong flavor of coffee, do not care how much fragrance, let alone how the bar serves the cup of coffee he chooses.

The concentration of coffee feels to be the demand of these guests. Even so, we can't deny the emotion that most people feel when they enjoy the aroma of coffee.

Fragrance, only fragrance, is the highest value of coffee. Coffee lacks aroma, like a person without temperament. Temperament can have different forms and portions, and fragrance also has its different components and presentation.

Coffee that loses its flavor always makes people feel defective. Spend money on coffee, mainly because of its fragrance.

Through this article, we will look at the possible reasons why the coffee is stale or tasteless.

In the past, we have repeatedly mentioned that the quality of a cup of coffee comes from four important stages, namely:

1. Coffee plantation management: including varieties, planting environment and climatic conditions, fertilization, irrigation, pest control, etc.

two。 Post-harvest treatment methods: including harvest methods, post-harvest preservation, post-processing methods, cleanliness and hygiene of treatment sites, drying methods, storage methods and environment, and shelling process. And then there is the transportation process.

3. Baking method: including the understanding, operation and preservation of roasted coffee beans.

4. Make coffee.

In other words, in the above stages are shaping the quality of coffee, but also due to improper operation, so that the quality of coffee defects.

The following are the main points mentioned in the Coffee Cup Tester Handbook, which is about the timing of corruption and defects in the aroma of coffee beans, which is worthy of our coffee workers' reference:

The first stage occurs during harvest and drying.

When farmers dry coffee fruits or coffee beans, they will reflect the aroma of coffee beans and, in serious cases, cause rotten smell.

When harvesting coffee fruit, if the fruit is left in the coffee garden for too long, the bad smell in the garden will continue to be produced, and the enzymes inside the fruit will begin to break down the substances in the seeds.

Because of chemical changes, arabica coffee beans produce "Rioy" and robusta "rubbery".

Rubber flavor rubbery

In the drying stage, if the coffee fruit is placed in a high-temperature and humid environment, the action of internal enzymes is accelerated to produce "fermented flavor" (fermented).

(explanation: this is why it is repeatedly stressed that the peeling work should be completed on the same day after the coffee fruit is harvested, or the peeling should be carried out within 24 hours, and do not pile up for too long. )

Fermented flavor fermented

In general, coffee beans are laid on the cement floor, or in a high sun-drying bed, or on plastic cloth.

The main purpose is to keep the sun shop clean and clean so as to avoid pollution. If the coffee beans are placed in an unclean place, especially when the soil is dry, the oil inside the beans absorbs the smell of the soil and produces a "earthy".

Earthy earthy

If you put coffee beans in wet places, it is easy to cause mildew and produce a "moldy smell" (musty). If you use mechanical drying, when the drying speed is too fast, the oil inside the beans will decompose, resulting in a "skin stink" (hidy).

Smelly hidy

(explanation: mildew seems to happen slowly. In fact, because the environment is humid or drenched with Rain Water, coffee beans get moldy very fast, about 1-2 days, you can see the appearance of moldy phenomenon. In fact, when you see the appearance of mildew, it has been moldy for some time. )

The second stage occurs in the storage stage, which is the aging stage of coffee beans.

This stage is from harvest and drying to the period of baking.

In the first few months after harvest and processing, coffee beans have a unique grass smell, like the smell of freshly harvested alfalfa, known as "grass" (grassy). Grass flavor grassy

The enzyme inside the raw bean continued to function, and after a few months, this aroma characteristic gradually decreased. Until it is shipped and sold, it is called "new crop", that is, "seasonal beans".

(explanation: fresh beans that have just been harvested have their own characteristics as well as their unavoidable smell of green. This is also the reason why foreign beans are not in a hurry to ship after harvesting and processing. Is to reduce the smell of green. )

When coffee beans are properly stored, the speed of enzyme action will be reduced.

About a year later, these chemical changes began to reflect the various acids inside the coffee beans. The taste senses this change, and this coffee bean is already a "past crop". If the enzyme action greatly reduces the content of various acids after several years of storage of raw beans, the coffee beans are called "old beans or aged beans" (aged).

In addition to the enzyme action, coffee beans slowly lose organic matter and gradually produce a hay-like "straw smell" (strawy).

Straw flavor strawy

A few years later, coffee beans continue to lose organic matter, resulting in an unacceptable "wood smell" (woody).

Wood flavor woody

The third stage occurs during baking, which is mainly coking.

When the baking temperature reaches 400 ℉ (204 ℃), the sugar inside the coffee bean continuously changes chemically: it combines with the organic and inorganic substances inside the coffee bean to form brown caramel.

As the heat increases, the sugar inside the raw beans will reflect the aroma contents.

If the heat is not enough, so that the coking process is not sufficient, the roasted coffee beans will have the smell of grass. The aroma is like the green bean (green peas) in green vegetables, called "stinky green flavor" (green).

Smelly green flavor green green bean green peas

If the heating process is too slow, the roasted coffee beans taste insipid and smell tasteless, which is called "roasted flavor" (baked).

If the baking rate is too fast-the edges of the coffee beans are obviously charred-the chemical changes are not complete, forming a "tipped". If the heat is too high, the surface of the coffee beans will be scorched, resulting in a "scorched smell" (scorched).

In the fourth stage, after baking, the coffee beans will exhaust.

After the coffee beans have been roasted, they begin to exhaust. At this time, the coffee beans are the freshest and full of aroma substances, most of which are volatile mercaptan or sulfur compounds.

After the coffee beans are ground into powder, a large amount of aroma will be lost. As the exhaust continues, more volatile organic matter, a water-soluble aromatic mixture in the fiber, will be lost with the release of carbon dioxide. The loss of this aroma results in the "flat" of coffee beans.

Coffee beans continue to exhaust and volatile organic matter continues to be emitted, resulting in "tasteless beans" (vapid).

If water and oxygen enter the coffee beans, the quality will be even worse.

First of all, the oil inside the coffee beans will be oxidized. Shadow to the coffee taste, resulting in a "light taste" (insipid).

Then, continued exposure to oxygen and moisture will accelerate the oxidation of linoleic acid and triglyceride, resulting in an unpleasant taste, a condition known as "stale" (stale).

Finally, the oil inside the coffee beans interacts with oxygen and water to produce an unpleasant quality, called "oil stink" (rancid).

Oily smelly rancid

The fifth stage is after brewing.

After the coffee is brewed (still), the aroma of coffee changes faster than at other stages.

After brewing, the coffee begins with the most "fresh" (fresh), that is, the most abundant volatile organic compounds that make up the coffee aroma.

If the effervescent liquid in an unsealed container is continuously heated, the action of active molecules and the increase in temperature make the loss of gaseous substances faster.

The brewed coffee first loses its aroma and becomes "flat".

Continue to heat up to evaporate the volatile matter, making the coffee "vapid".

Prolonging the heating time will affect the preservation of organic matter in the coffee solution.

Long-bond organic matter breaks into short-bond substances, which will increase the acidic taste, which is called "sour astringent taste" (acerbic). It is proved that the coffee contains chloric acid.

Secondly, due to the evaporation of water, the salt concentration in the solution is relatively increased, forming a "saltwater flavor" (briny).

Saltwater flavor briny

If you continue to heat the protein and turn the coffee liquid into a gel, there will be a "tar flavor" (tarry).

Tar flavor tarry

Finally, the concentration of alkali-containing substances in the coffee solution increased, its bitter taste plus salt, showing a "salt" (brackish).

(Fin)