Coffee Knowledge the “flavor spectrum” is not as complicated as the “odor spectrum” introduced in the previous chapter. Some sour and new aromas are only volatile and need to be identified by anger; some are non volatile, only water-soluble, and need to be identified by taste buds; others are acid silver components that are both volatile and water-soluble, so the sourness and New flavors can often present the dual senses of aversion and taste.
Coffee has only four water-soluble flavors:
As for the bitter and salty tastes, they are not volatile and cannot be smelled with the nose. They are purely the taste category of taste recognition.
1. The taste of coffee is revealed
The performance of the four major flavors of coffee, such as sour, sweet, bitter, and salty, is closely related to roasting. Therefore, the “flavor spectrum” is classified into light medium roasting and deep supplying heavy roasting. Coincidentally, the shallow and medium roasted “sweet and sour” flavors have a low molecular weight, high polarity, and high water solubility, and they dissolve in the first half of the extraction.
However, the “bitter salty” flavors have higher molecular weights and lower macro-polarity and low water solubility, and they dissolve in the latter half of the extraction.
The taste of light roast to medium roast is dominated by the sweet and sour taste of low molecular weight and medium molecular weight. However, there are too many beans or improper roasting. Even light roast will have an unflattering bitter and salty taste. As for deep roasting, it is based on high-molecular-weight bitterness and saltiness. Unless you are familiar with the deep roasting of traditional drum roasters, it is difficult to break the fate of deep roasting beans with salty and bitter taste.
But deep roasting is not useless. The rarest deep roasted flavor spectrum-“bitter and not bitter, sweet and soothing” is not a myth after experimentation.
70% to 72% of roasted coffee beans are insoluble fiber, and water-soluble flavor components only account for 28% to 30% of the weight of cooked beans. What is the content of these soluble flavors?
SCAA senior consultant Ringer’s masterpiece “Coffee Cup Tester’s Handbook” contains relevant data, and the author slightly organizes it as the following table:
The above data is the weight percentage of sour, sweet, bitter, and salty soluble flavors of coffee cooked beans. Although the sweetness component is the largest, accounting for 39% of the solubles, the bitterness is second by 26.4%, and the saltiness is ranked at 14%. Third, the proportion of sourness is the lowest, only 5.4%, and the total is 84.8%. The rest are not listed, they should be flavored with less content.
However, Ringer did not specify the baking degree of the sample. Let’s take the cup to measure the usual moderate baking Agtron#55. Depending on the baking degree, these values will vary, but as long as the baking degree is within the palatable range, the above flavors account for The order of ratios will not change.
But don’t be literal and think that sweetness accounts for the highest proportion, and coffee should be as sweet as honey. This is not the case. The bitter, sour and even salty taste of black coffee can easily interfere with the sweetness, which involves the four flavors of sour, bitter, salty and sweet. Complicated mutual offset and mutual promotion. Only the green beans have thick cell walls, higher than average sucrose and amino acid content, and perfect baking, so that the sweetness can break free from the “encirclement and suppression” of other samadhi and stand out.
Therefore, sweetness is the most precious and happy taste of specialty coffee.
The four flavors of sour, sweet, bitter, and salty may appear in shallow-medium roasting, but when entering the world of deep roasting, organic acids have been cracked and exhausted, and the taste spectrum is simplified to three flavors of higher molecular weight, sweet, bitter, and salty. Let’s start with the “Taste Spectrum” of Shallow Baking and then discuss the “Taste Spectrum” of Old Baking.
2. “Taste Spectrum” of Middle Baking
Taste Spectrum of Shallow Roast·Sour Taste Spectrum: Tartness and Tannic Acid
Tartness: lively, bright, acid shock, wine sour taste, unpleasant taste, mixed acid, washing method
Tannic acid: softness, stuffiness, gradation, body fluid, sun exposure, wet planing, dense treatment
3. Aliphatic acids contribute to the sourness of coffee
Sour taste is the biggest feature of light-medium roasted coffee. Coffee beans contain various organic acids. Phenolic acids, aliphatic acids and amino acids have the greatest influence on the taste.
Ringer’s “Coffee Cup Tester’s Manual” pointed out that in terms of taste, if the concentration of amino acids (including cysteine, leucine, glutamic acid, and aspartic acid) is high, it is easy to have sweetness; if phenolic acid (Including chlorogenic acid and quinic acid) high in concentration, easy to have bitter taste; but fatty acids (including acetic acid, lactic acid, citric acid, malic acid, tartaric acid, formic acid) high in concentration and easy to have a sharp taste.
Although the aliphatic acid content of coffee accounts for 5.4% of the solubles, which is far inferior to the phenolic acid (accounting for 13% of the solubles), the fatty acid contains a large amount of hydrogen ions and is the main source of the taste of coffee.
Basically, aliphatic acids can increase the brightness of coffee, and it is easy to interact with the sweet, bitter, and salty flavors of black coffee, presenting interesting flavors. Among them, citric acid and malic acid are not volatile. They are the product of the metabolism of the coffee beans themselves. They are easily combined with the sugar of black coffee to reduce the unpleasant sour taste, and produce the acidity similar to wine, and increase the taste of light and medium roasted coffee. Liveness and layering, but citric acid and malic acid are resistant to fire, which decreases all the way from the beginning of baking.
It is worth noting that acetic acid and lactic acid (volatile aliphatic acids) are not the metabolic products of coffee beans themselves. Raw beans are almost free of them. There are two main sources:
First, the derivatives from the washing fermentation process, if the washing fermentation is excessive, the concentration of acetic acid and lactic acid will soar, resulting in a disgusting rancidity.
Second, from the baking process, sucrose degradation products, from shallow to medium baking, the sucrose is degraded, and the concentration of acetic acid and lactic acid rises, but when it reaches a certain point, it drops sharply in an instant. Therefore, the sour taste of light to medium baking is obvious. , But after entering the medium-deep roasting, the lactic acid and acetic acid quickly collapse, and the sour taste is reduced.
In short, citric acid, malic acid, acetic acid and lactic acid are responsible for the sourness of light roasted coffee, but too high a concentration can be a bad thing, especially the sharp sourness caused by over-fermented acetic acid and lactic acid is the most unpleasant.
Taken from Viani, R. In Caffeine, Coffee, and Health. New York, 1993.
From Figure 3, we can see the proportion of aliphatic acids in raw and cooked beans. Please note that citric acid and malic acid are significantly reduced after baking, while acetic acid and lactic acid do the opposite. In light to medium baking, there will be hyperplasia.
Studies have found that moderate baking, when the weight loss rate is between 13% and 15%, the content of various aliphatic acids is the largest, and then it degrades rapidly, and the sourness gradually becomes pure. What is interesting is that quinic acid or quinine vinegar, which is a phenolic acid, is a product of chlorogenic acid degradation. It will increase with baking and will not collapse until it doubles.
4. The fermented taste that is too sour
Washed beans are obviously more sour than sun-dried beans, mainly due to the higher content of acetic acid and lactic acid in washed beans. Sun-dried beans have more salt minerals, which neutralize the acidity of black coffee, so the acidity is more gentle and harmonious, but the ingredients of sun-dried or semi-washed treatments are more complex, and the cleanliness and translucency are poorer, so the acidity is better than water-washed Bean is dull.
Tartness, liveliness and translucent are the characteristics of shallow-medium roasted water-washed beans, while tannic acid or muffled acid is the characteristic of sun-dried beans, but over-fermented sun-dried beans or honey processing methods will also have an appalling sour taste.
Active acid is certainly an important taste of light roasting, but pay attention to the cupping, the taste is pleasant and dynamic active acid, or frowning dead acid. The so-called lively acid refers to the entrance of the fruit acid. The “sour shock” melts in a few seconds and elicits the sweet and sour taste of the fruit, the sweet and sour taste in the acid. It is not an exaggeration to call it “sweet and sour shock”.
As for the dead sour that is over-fermented, it means that it is sour all the way to the end, like sticking to the tongue, lacking the rhythm of feathering, and unbearable. The acid-base value (PH value) of light-medium roasted coffee is about 4.8 ~ 5.1, medium-deep roasted coffee is above 5.2, and the acidity of deep roasted or re-roasted coffee is lower, above 5.4. As for the over-fermented tart coffee, the pH value is often lower than 4.8.
For the acidophiles of the light-baked pie, did you drink normal active acid or over-fermented dead acid? Don’t get caught up in it and treat the sourness of over-fermentation as a delicacy in the world.
5. Miscellaneous odors from repeated heating
There is also a problem of miscellaneous acid that deserves our attention. Everyone has an experience. After brewing the American filter coffee machine, continue to heat it at 80°C for 20 minutes. After 20 minutes, the aroma disappears, and the active acid turns into a bad sour taste, even a slightly salty sauce.
According to the research of two scholars, Hucke (J) and Maier (H), this is because the thiol is oxidized and tastes off. In addition, during baking, part of quintic acid is dehydrated into slightly bitter and non-sour taste. “Quinide vinegar” (Quinindé), once brewed into coffee, it will have a pleasant slightly bitter taste, but if black coffee is kept at a temperature above 80°C for a long time, the quinine ester will be hydrolyzed into more hydrogen ions and Quintic acid increases the unpleasant sour taste. If the black coffee is kept warm for over one hour, the pH value will drop to below 4.6, with a strong sour taste.
The interesting thing is that after the coffee is brewed, don’t keep it warm and let it cool naturally. Although the sourness is enhanced, it is not a sour taste but a clean and clear sour aroma with more sweet and sour fruit and brown sugar to taste, which is worth the aftertaste. .
The “sour spectrum” may be classified in this way. Fatty acids, especially fruits, can improve the brightness, dynamics and acidity of coffee. However, do not regard the over-fermented acetic acid and lactic acid as smooth, high-quality acids. In addition, it is best not to heat the coffee after brewing, to prevent the fragrant acid from oxidizing into miscellaneous acid.
As for the phenolic compounds, they mainly come from the degradation products of chlorogenic acid, which have a far greater impact on bitterness than sourness.
Bitterness is one of the four major flavors of coffee, but it is non-volatile and only water-soluble. Therefore, many people are afraid of bitterness and would rather smell coffee than drink coffee. The bitter taste of coffee can be classified into two types: smooth and unpleasant. The former refers to the natural slight bitterness of caffeine, fenugreek, aliphatic acids and quinine vinegar; the latter is unpleasant and bitter, which refers to the degradation of chlorogenic acid. Chlorogenic acid lactones (Chlorogenic acid lactones), blemish beans and the heavy bitterness of carbonized particles. It can be said that the good roasting technology is related to whether the bitterness of coffee is pleasant or unpleasant.