Sweet Maria's Coffee Glossary

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Acetic Acid
Acetic acid can lead to vinegar-like flavors in over-mature coffees, or bitterness in high quantities. But in moderate amounts it adds a positive winey note to the cup. Acetic acid classifies as an organic acid, and is one that can be detected by smell.
Related Terms:
Citric Acid Phosphoric Acid Malic Acid Vinegar Winey Liveliness Chlorogenic Acid Brightness Ferment
Categories:
Flavor Chemistry


Acidity
Acidity in arabica coffees is almost always considered a positive flavor attribute, yet the term can sound unattractive. People may relate acidity to stomach discomfort, or to sour flavors. This would be incorrect. The acidity in good high-grown arabicas imbues the cup with delicate flavor accents, complexity, and dimension. Good acidity is fleetingly volatile, a momentary sensation, giving effervescence to the cup, and informing the mouthfeel as well. Coffees with no acidity can taste flat. Acidity is not about quantity, it is about quality, and good coffees have a complex balance of many types of acidity: malic, citric, acetic, phosphoric, quinic, to name a few ... and a whole set of chlorogenic acids that are very important to flavor experience as well. Kenyas, which by flavor are some of the higher acid coffees, actually have measurably less than Brazil arabicas (of quinic and citric acids), more of others (malic, phosphoric) and far less than some robusta coffees (chlorgenic acids)! Dark roasts tend to flatten out acidity in flavor. But contrary to the taste, darker roasts have more acidity than lighter roasts. So quantity does not always follow perception. Acidity in coffee might be described by terms like bright, clear, effervescent, snappy, dry, clean, winey, etc. Coffees without acidity tend to taste flat and dull, like flat soda. Acidity is to coffee what dryness is to wine, in a sense. Different coffee origins will possess different kinds of acidity; like the wine-like high notes of some African coffees versus the crisp clear notes of high grown coffees from the Americas. Unpleasant acidy flavors may register as sourness.
Related Terms:
Citric Acid Phosphoric Acid Malic Acid Acetic Acid Chlorogenic Acid Liveliness Brightness
Categories:
Flavor Chemistry


Acids
Many acids contribute to coffee flavor; malic, citric, quinic, tartaric, phosphoric, etc. See ACIDITY or specific acids. While acids in coffee sounds like a bad term, and one that leads to stomach discomfort our sourness, this is not usually true. Drinking coffee with no food in the digestive system can lead to discomfort since coffees have enough oils to trigger digestive acids. Eat before or while taking morning coffee.
Related Terms:
Citric Acid Phosphoric Acid Malic Acid Acetic Acid Liveliness Brightness Acidity
Categories:
Chemistry


Aldehydes
Along with Ketones, Aldehydes are an important factor in coffee aromatics, partially formed in roasting by the interaction of fatty acids and oxygen. They are partially formed by the Strecker Degradation of amino acids in the coffee roast environment.
Related Terms:
Ketones Strecker Degradation
Categories:
Chemistry


Caffeine
An alkaloidal compound that has a physiological effect on humans, and a slight bittering flavor. It is found throughout the coffee plant but is more concentrated in the seed / coffee bean. Arabica ranges from 1.0 to 1.6% caffeine, and Robusta (Coffea Canephora) from 1.6 to 2.2% caffeine. It is highly water soluble. The amount of caffeine in brewed coffee is directly proportional to how much ground coffee was used to make the cup. See the Caffeine FAQ for more: http://coffeefaq.com/site/node/25
Related Terms:
Bitter Acetic Acid Malic Acid Phosphoric Acid Citric Acid Robusta Arabica
Categories:
Chemistry


Caramelization
Caramelization is slower than Maillard reactions, and requires higher temperatures. These reactions involve only sugars. They really begin up around 150C to 180C, with water being lost from the sugar molecule beginning the chain of events. In all cases the sugar is converted to a furfuryl. These are a type of furans that have a caramelly, slightly burnt and also slightly meaty notes. The same compound is produced via a different route in the Maillard reactions. However it is with prolonged high temperature that many other types of aromas are generated. Caramelisation is more predictable than Maillard reaction due to less variation in the starting compounds. Without the sulphur or nitrogen found in the amino acids caramelization is unable to produce flavors as meaty as Maillard reactions. It is interesting to note how the sugar solutions taste changes in caramelization. A sugar solution initially will be sweet with no aroma. Through caramelization it becomes both sour and a little bitter, as a rich aroma develops. Generally the longer sugar is caramelized the less sweet it tastes, so the key is to balance the benefits of uncaramelized sugar sweetness while avoiding light roast astringency and sourness.
Related Terms:
Maillard Reaction Pyrolysis Roasting Roast Taste
Categories:
Chemistry Roasting


Cellulose
Cellulose is the principle fiber of the cell wall of coffee. It is partially ordered (crystalline) and partially disordered (amorphous). The amorphous regions are highly accessible and react readily, but the crystalline regions with close packing and hydrogen bonding may be completely inaccessible. Native cellulose, or cellulose 1, is converted to polymorphs cellulose III and cellulose IV when exposed to heat. Coffee's structure is a well developed matrix enhancing the mass uniformity and aiding in the even propagation of heat during roasting. Cellulose exists in coffee embedded in lignocellulose (an amorphous matrix of hemicellulose and lignin containing cellulose), making up the matrix cell walls. Hemicellusloses are polysaccharides of branched sugars and uronic acids. Lignin is of special note because it is a highly polymerized aromatic. Severe damage occurs to the cell walls of the matrix at distributed temperatures above 446 degrees F and bean surface temperatures over 536 degrees F The actual temperature values will change due to varying levels of other constituents. Second crack, associated with darker roasts, is the fracturing of this matrix, possibly associated with the volatilization of lignin and other aromatics. Under controlled roasting conditions, the bean environment temperature should never exceed 536 degrees F. A wider safety margin would be achieved by limiting the maximum environment temperature to 520 degrees F. These temperature limits minimize damage to the cell matrix and enhances cup complexity, roasting yield, and product shelf life.
Related Terms:
Roasting First Crack Second Crack Origin Flavor Pyrolysis Maillard Reaction Caramelization
Categories:
Chemistry


Chemical Process
A decaffeination method where beans are soaked in hot water, which is then treated with a chemical that bonds to caffeine (either methylene chloride or ethyl acetate).
Related Terms:
Decaffeinated Coffee
Categories:
Chemistry


Chlorogenic Acid
Chlorogenic acids (CGAs) are important to coffee flavor, contributing to flavor when in the proper balance and level. They are a group of phenolic acids esterified to quinic acid, and account for up to 10% of the weight of green coffee. They are known to have antioxidant properties. Like all acids, its levels are reduced in roasting; darker roasts result in less acidity in the cup. Since it reduces to quinic acid in roasting, and quinic acid in high levels results in perceived bitterness and sourness, too much CGA is not desireable. Robusta coffees have roughly 25% more CGA than arabica!
Related Terms:
Phosphoric Acid Malic Acid Acetic Acid Liveliness Brightness Acidity Citric Acid
Categories:
Flavor Chemistry


Citric Acid
Citric acid is, in moderate amounts, a component of good, bright coffees. It is a positive flavor acid in coffee that often leads to the perception of citrus fruits and adds high notes to the cup. Fine high-grown arabica coffees have more citric acid than robusta types.
Related Terms:
Acetic Acid Chlorogenic Acid Liveliness Brightness Malic Acid Phosphoric Acid Acidity
Categories:
Flavor Chemistry


Emulsion
In coffee, "emulsion" typically refers to the suspension of coffee oils in water. While brewed coffee is primarily an extraction, espresso is both an extraction and an emulsion because it occurs under pressure.
Related Terms:
Espresso Brewed Coffee Extraction
Categories:
Chemistry Brewing


Endothermic
A term applied to chemical reactions, referring to a reaction that absorbs heat. Most parts of the coffee roasting process are endothermic.
Related Terms:
Exothermic Roasting
Categories:
Chemistry Roasting


Esters
An ester is an often fragrant organic or partially organic compound formed by the reaction between an acid (including amino acids) and an alcohol. They play a smaller role in coffee aromatics than Ketones and Aldehydes, but can be distinct fruit flavor contributors.
Related Terms:
Ketones Aldehydes
Categories:
Chemistry


Exothermic
A term applied to chemical reactions, referring to a reaction that releases energy. A classic example is burning. Most parts of the coffee roasting process are endothermic, but first crack is exothermic.
Related Terms:
Endothermic Roasting
Categories:
Chemistry Roasting


Extraction
Refers to the process of infusing coffee with hot water. Hot water releases or "extracts" the flavor from the roasted, ground coffee.
Related Terms:
Brewed Coffee Brewing
Categories:
Chemistry Brewing


Furans
Furans are important contributors to coffee aroma, contributing to sweet, nutty, fruity or caramel-like smells. They are derived mainly from sucrose and Polysaccharides during roasting, a product of caramelization. It is estimated there are 126 possible furans found in coffee.
Related Terms:
Aldehydes Ketones Pyrans Phenols
Categories:
Chemistry


Ketones
Along with Aldehydes, Ketones are important carbonyl compound that contribute over 20% to coffee aromatics. Formed from carbohydrates in the roast process, they result in aroma and flavor ranging from floral, herbaceous, buttery, caramel, vanilla, milky, saffron, beef, etc.
Related Terms:
Aldehydes
Categories:
Chemistry


Maillard Reaction
The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, induced by heat in the coffee roasting process. It results in the browning color of coffee (from melanoidins, which are key to espresso crema too), as well as many volatile aromatics and flavors. It is not unique to coffee, and is at work in a variety of food conversion or cooking operations: toasted bread, malted barley, roasted or seared meat, dried or condensed milk.
Related Terms:
Caramelization Roasting Pyrolysis
Categories:
Chemistry


Malic Acid
Malic acid is yet another of the many acids that adds to favorable perceptions of cup quality; malic acid often adds apple-like flavors. In Kenya coffees, it reaches levels of 6.6 g/kg whereas robusta coffees measure about about one-third to one-half of that level.
Related Terms:
Acidity Brightness Liveliness Chlorogenic Acid Acetic Acid Phosphoric Acid Citric Acid
Categories:
Flavor Chemistry


Phenols
Phenols are a set of organic compounds, relatively stable, that contribute to coffee aroma and flavor. They can have negative characteristics: tarry, smokey, medicinal, woody, leathery. But, especially at lower levels, can be spicy, vanilla, clove, anise, even floral in nature. Phenols are mainly derived from Chlorogenic acids.
Related Terms:
Ketones Aldehydes
Categories:
Chemistry


Phosphoric Acid
One of many acids that contribute to positive flavor perception in coffee. More phosphoric acid might lead to the sense of higher acidity overall. Since perception of acidity gives a cup finer cup quality, brightness and vibrancy, phosphoric acid is considered desirable in arabica coffees. It itself, it is very tart. Also noteworthy is the fact it is not an acid that can be detected by smell, and is not an organic acid.
Related Terms:
Phosphoric Acid Malic Acid Acetic Acid Liveliness Brightness Acidity Citric Acid
Categories:
Chemistry


Pyradines
Pyradines are a product of pyrolysis involving sugars and amino acids, and other routes. They are mainly responsible for harsh notes: bitter, astringent, roasty, burnt notes, but can also give hazelnut, tobacco, anise, floral and other aromas.
Related Terms:
Esters Ketones Aldehydes Phenols Furans Bitter
Categories:
Chemistry


Pyrans
Pyrans are related to Furans, aromatic compounds in coffee, derived from sugars. Also referred to as Pyranols and Pyranones, one of the more important is called Maltol, having fruity, caramel sweetness, jam-like, pineapple, strawberry descriptors attached to it.
Related Terms:
Esters Ketones Aldehydes Phenols Furans
Categories:
Chemistry


Pyrolysis
Pyrolysis is the chemical decomposition of a condensed substance by heating. It is a special case of thermolysis, and is most commonly used for organic materials. At lighter levels, caramelization of sugars is an important result of the pyrolysis of coffee, the release of CO-2, and a host of other chemical and physical changes in the coffee. There are two stages of pyrolysis in coffee which we call "First Crack" and "Second Crack." Extreme pyrolysis, which leaves only carbon as the residue, is called carbonization and leads to charred flavors in very dark coffee roasts. Pyrolysis often occurs spontaneously at high temperatures, for example in fires and when organic materials come into contact with lava in volcanic eruptions, and has been assumed to take place during catagenesis, the conversion of buried organic matter to fossil fuels. It is an important chemical process in several cooking procedures such as baking, frying, grilling, and caramelizing. It's important to note that chiefly involves the conversion of carbohydrates (including sugars, starch, and fiber) and proteins.
Related Terms:
First Crack Second Crack Roasting
Categories:
Chemistry


Pyrroles
There are 70 identified Pyrroles in coffee, important aromatic compounds, thermally formed by a reaction of aldoses with amino acids in the Maillard group of roast reactions. Pyrroles are derived mainly from trigonelline according on one source. In general they relate to unfavorable flavors characteristic of trigonelline bitterness; metallic, earthy, musty, oily, alliaceous, garlic, mushroom, etc.
Related Terms:
Pyradines Furans Phenols Aldehydes Ketones Esters
Categories:
Chemistry


Quinic Acid
Qunic acid is another double-edged proposition in coffee. In moderate amounts it adds a slight astringency, positive in brighter coffees such as Kenyas or high-grown Centrals. Because of how it reacts with salivary glands, this can lead to heightened senses of body. But too much leads to sour, unfavorable astringency. Chlorogenic acids are largely transformed to quinic acids in the roast process. Quinic Acid melts in pure crystalline form at 325 degrees E, well below the temperatures associated with the roasting environment. Quinic Acid is water soluble and imparts a slightly sour (not unfavorably as in fermented beans) and sharp quality, which adds to the character and complexity of the cup. Surprisingly, it adds cleanness to the finish of the cup as well. it is a stable compound at roasting temperatures.
Related Terms:
Chlorogenic Acid Acidity Brightness Liveliness Acetic Acid Malic Acid Phosphoric Acid Citric Acid
Categories:
Chemistry


Rust Fungus
Rust Fungus is a big problem in Colombia, but is found in many coffee producing countries. Known as La Roya in the Americas, this disease diminishes fruit production and ultimately kills the plant. Combating the disease with selectively-applied fungicides, especially in seasons with heavy rains, is key to saving the coffee plants.
Related Terms:
Defects Origin
Categories:
Chemistry Biology/Cultivars Trade Terms


Sparkles
Sparkles is a key coffee quality term, and refers to brightness in the cup. Bright things often shine, both visually and in a gustatory sense, and that is expressed among tradespeople as sparkley, sparkles, or "this coffee is well-sparkled." It is not related to crystals, as in the proprietary "flavor crystals".
Related Terms:
Bright Acidity Effervescent
Categories:
Flavor Chemistry Sweet Maria's Terms


Strecker Degradation
The Strecker Degradation is an interaction of amino acids (AKA proteins) with a carbonyl compound in an environment with water, resulting in the creation of CO2 and an Aldehyde or Ketone. The later two components are important for volatile aromatics and flavors, and the Strecker Degradation contributes to browning. It involves compounds formed in the Maillard reaction and is therefore necessarily linked to it in coffee roasting.
Related Terms:
Pyrolysis Maillard Reaction Roasting
Categories:
Chemistry


Sucrose
Sucrose is largely destroyed by the roasting process through various reactions and thermal caramelization. It is destroyed at this rate: 2.9% remains in a light roast; 0.9% in a medium roast, 0% in a dark roast. Sucrose is sweeter before caramelization, but perhaps more aromatic after caramelization. Still, if there is no sweet taste, the perception of caramelized sucrose will not be sweet. "Sucrose is the principle sugar in coffee. The melting point of pure crystalline sucrose is in the 320-392 degrees F with 370 degrees F most commonly accepted. Degradation of dry sucrose can occur as low as 194 degrees F. and begins with the cleavage of the glycosidic bond followed by condensation and the formation of water. Between 338 and 392 degrees F, caramelization begins. It is at this point that water and carbon dioxide fracture and out-gassing begins causing the first mechanical crack. These are the chemical reactions, occurring at approximately 356 degrees F, that are exothermic. Once carmelization begins, it is very important that the coffee mass does not exotherm (lose heat) or the coffee will taste "baked" in the cup. A possible explanation is that exothermy of the charge mass interrupts long chain polymerization and allows cross linking to other constituents. Both the actual melting point of sucrose and the subsequent transformation, or caramelization, reaction are effected by the presence of water, ammonia, and proteinatious substances. Dark roasts represent a higher degree of sugar caramelization than light roasts. The degree of caramelization is an excellent and high resolution method for classifying roasts."
Related Terms:
Sweetness Trigonelline Roast
Categories:
Flavor Chemistry


Tannic
The term Tannins refers to the use of wood tannins from oak in tanning animal hides into leather. Having the bitterness or astringency of Tannins. Tannins are plant polyphenols found across the flora kingdom.
Related Terms:
Bitter Acetic Acid Malic Acid Phosphoric Acid Citric Acid Robusta Arabica
Categories:
Flavor Chemistry


Trigonelline
Trigonelline is a bittering compound that is reduced as the roast gets progressively darker. Trigonelline is 100% soluble in water and therefore will end up in the cup. Trigonelline is probably the most significant constituent contributing to excessive bitterness.
Related Terms:
Phenols Aldehydes Ketones Esters Pyradines Furans Bitter
Categories:
Chemistry