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How We Taste Tea
The flavor of tea is a complex perception. There is a certain flavor dynamic. What is meant by the dynamics of flavor? Most teas can be described as having a foreground (top note) flavor, middle ground flavor and background flavor. These combine to produce a profile, a "flavor profile". For example, there is a "flavor profile" into which all Darjeelings will fall simply because they are Darjeelings or all Keemuns or all Yunnans or all Assams, etc. The reason is because all of the individual leaves of each growing region are basically identical. However, a well-balanced profile of each growing region falls within specific profile outlines. An unbalanced profile looks ragged (somewhat like a saw blade) and therefore becomes somewhat less than pleasant to drink. This unbalanced profile can be caused by many things: low altitude, improper pluck, poor processing, bad manufacturing, exposure to water or excessive moisture, to name a few. Tea is like the little girl: when it is good it is very, very good and when it is bad it is horrid.
Flavor is a combination of two sensory perceptions: taste and odor or aroma. The first part of the flavor duo of taste and aroma is perceived by the taste buds and other sensory tissues on the tongue. It is this area which perceives non-volatile stimuli such as: salt, sweet, acid (sour) and bitter. (Occasionally considered also as a functional perception is the taste sensation of metallic, but this may also be caused by medication, metals used to fill dental carries and several other extraneous causes.) These taste buds are generally located in very specific areas on the tongue (sweet in front, salt next and along the sides, acid (sour) next and along the sides, bitter in the rear and from side to side covering the back of the tongue). However, all types of taste buds can be found located sparsely throughout the tongue's entire surface.
Secondly, one must consider the sense of smell when discussing what makes up flavor perception. One's sense of smell, or odor, is one's reaction to the stimulus of volatile components found in the tea which we consume. When one is swallowing tea there are volatile components present. It is these volatiles that evaporate up into the nasal cavity (retro-nasally) and stimulate the nerve endings in the olfactory bulb region. The fact that we are also smelling food as we are tasting it is the reason why we cannot "flavor" things well when we have a cold. It is also the reason why it becomes difficult, if not impossible, to discern the difference between an apple and a potato when we tightly hold our nose and chew them separately. The texture is similar and that is all that we seem to perceive.
Besides these two sensory perceptions, the physical aspects of tea come very much into play:
One theory of flavor perception, although somewhat antiquated, is Amoore 5 Stereochemical Theory. It is an old theory but it remains a good model for explaining many aspects of flavor perception. It treats volatiles as jigsaw pieces that can fit into various receptor "holes" in the nerve endings of the olfactory bulb. The shapes of these "holes" can be categorized into different groups. These groups correspond to specific odor types, the so-called simplest or most basic odors in nature (which I have put into 10 groupings). The theory states that all flavors can be described as combinations of these simplest odors. More recent theories postulate a model of odor perception which makes the analogy between odor perception and the similarity of chemical action of an enzyme on a substrate or one layer of receptors lying under another on the nerve endings and that the odor molecules penetrate down through these layers thus prompting many subtle flavor changes.
In either of the above models, the odor (flavor) molecules (also called odorovectors) generally have a particular molecular shape. Sulfur, as an example, is identifiable all over the world but cultural food flavors are not. However, some molecules are quite elastic and can conform to many shapes (multi-odorovectors) while other molecules are quite rigid and conform only to certain odor (flavor) shapes and thus only certain receptors (vanilla, e.g.).
When a molecule fits into a specific "jigsaw slot", the nerve ending which corresponds to that receptor site is then stimulated. The nerve ending then sends a message to the brain. At the EXACT instant that the flavor is perceived by the brain, the flavor becomes characteristic of that "fit". Thus all Darjeelings fit a certain flavor patter for immediate identification by the brain (if one has cupped a number of Darjeelings for the brain to build up an identity databank).
Some molecules can fit into more than one site and therefore, the molecules of the mixture will stimulate a number of different nerve endings at different sites, and at different levels, all at once. Since no flavor profile can be discerned by the brain, it literally gives up on an identity search and selects one which it can identify (in other words, the brain guesses). We now have a blend, and in our case, a tea blend.
A chemical (in tea, an enzyme or an essential oil or a combination thereof) which has the property of being able to stimulate differently-shaped sites at once is said to be a secondary aromatic compound (call it "after taste" if you like). The analogy here is that primary odorants or flavorants are like letters of the alphabet, and the secondary odorants or flavorants are like syllables. I like that description — it almost sounds as though tea talks to one as it allows itself to be drunk (as I'm sure it does).
The flavor system — the nose and tongue — is one of the most sensitive of all of our senses and, perhaps because of this, the most easily fatigued. When a Tea Master has been cupping tea for a long period of time on a project that requires crucial flavor judgment, he (she) might wash out his (her) mouth with water or chew on an unsalted cracker in order to aid in his (her) perception, but when nerve endings are fully desensitized by overstimulation these are just temporary aids — not cures. Only time will help and usually somewhere between forty and fifty hours are needed to restore flavor acuity and judgment.
Perception of tea depends a lot upon the system used to prepare the tea since the method of preparation preserves or destroys the aromatic compounds. Below is a sequence of steps in the flavor release of tea compounds:
(Believe me, all of this happens within milliseconds. This is why, as many of you have witnessed, I need take just one sip of a freshly and correctly infused tea and am able to form a judgment on that tea immediately.)
Each molecule of a flavor aromatic has a particular size and weight. The larger the molecule (or the more atoms the molecule has in it) the lesser the rate of evaporation — they are heavier. The smaller the molecule (or the less atoms the molecule has in it) the more the rate of evaporation — they are lighter. Light compounds are generally perceived as top notes. Heavy compounds are generally perceived as base notes. In between are simply hundreds of nuances.
Volatilization or degree of evaporation (retro-nasally) is dependent on many factors. The temperature of the tea and the surface area of the cup or spoon changes both volatility and evaporation rate. If I cup a tea using a cup with a surface diameter of 9 cm and an exact tea cupper's spoon and at a temperature of 200 degrees, and if you, at home, use a cup with a surface diameter of 7 or 11 cm, a tablespoon and at a temperature of 130 degrees, are we then cupping the same tea? Obviously, we are not. Can you understand how the dynamics of the flavor profile will change?
Volatile flavor components can be generated in a number of ways. Fermentation causes one type of flavor, as esters, as well as alcohols, and trace sulfur and other components are formed. Oxidation is another avenue of flavor component generation. Heating, cooking or browning causes yet other flavor components to be generated. Pickling or brine bathing creates others. Included in these mechanisms are caramelization, and Maillard Browning. Browning, regardless of the process, forms a host of complex compounds including (but not limited to) pyrazines, thiazolines, pyrolles, and aldehydes. Some flavors of food are formed by the food itself, for instance, the seeds of a raspberry leach their woody oils into the pulp of the fruit. This compound, ionone, is injected into the fruit by the seeds and this is what gives raspberries their unique "raspberry" flavor. Some flavors of teas are formed by the tea itself. The flavor components unique to a specific tea are generated by a combination of polyphenols and essential oils. Again I repeat: there is a flavor profile for all Darjeelings, etc.
I have only touched on the complexity of the flavor system (tongue and nose). It becomes obvious to someone who must use and rely on this flavor system every day how important it is to know the crucial factors which affect flavors and one's perception of them. In other words, the system influences the flavor. It must be emphasized that I, as a Tea Master, must work with a specific tea in a specifically defined system of tasting in order to evaluate that tea. I, or anyone, must only compare Assams to Assams, Darjeelings to Darjeelings, Keemuns to Keemuns, etc. If I do not approach Tea Tasting (cupping) using this approach, the whole process of flavor submission and evaluation becomes nothing more than a throw of the dice.
Within the flavor detection studies I have done through the years, I have found 10 families of primary flavor compounds. Some of these pertain to tea, others do not. I, however, must know and be familiar with all of them. The order of the descriptive terms that follow go from light or top notes to heavy or base notes. I also point out that I do not publish these flavor groupings for your or anyone's approval —THEY SIMPLY WORK FOR ME.
The acid group is the first category. Characterized by the organic acids, this blend is a homologous series of C-1 (formic acid) to C-12 (dodeconoic or lauric acid). Organic acids are responsible, in part, for the aroma of dairy products: Cheeses, yogurt, etc. They also play a major role in giving lift (top note) to fruit flavors and wine for example. Acetic acid is probably the most familiar compound in this group, being the active flavorant of vinegar.
The ester group is next (again represented by a homologous series of ethyl esters). This series is responsible for the sweet, fruity aromas found for example in apple, wine, as well as the characterizing compounds in cognac. As compounds in the series evaporate, the heavier, waxier compounds remain. Note the confusion when describing a product as sweet. The tongue perceives one kind of sweetness (sugar). But, we will also see that besides this, the estery character, there are other aroma-sweet types. It is, therefore, far more accurate to describe a flavor for example as sugary-sweet or estery-sweet.
Oftentimes, the estery characteristic is described as perfumy. This is a misnomer. Perfumyness is really attributable to the presence of the pungent/floral compounds (see later).
Greenness is an odor characteristic of the green-colored or the unripened foods. Chemically, the green odors can be associated with the presence of at least one (or more) double-bound, (or a triple-bound, or any combination of the two). This chemical unsaturation, as it is called, can be present alone, or in association with a combination of an alcohol, ester, or aldehyde group. The heavier (high molecular weight) compounds smell fatty. As a group, these chemicals are found in food products which could be described as either green and/or fatty. Chemically, therefore, greenness and fattiness are closely related. The compounds in the Green odor mixture, are responsible for the odor of leaves, green bananas, etc.
The next odor class is known as the Aromatic Terpenoids (Terpenes). Terpenes are combination of a chemical compound known as isopentene. Found in most essential oils, to a greater or lesser extent, the terpenes can range in flavor from citrus-like, piney, and terpentine, to minty, musty or camphor-like. These compounds could also be considered sweet. Therefore, the description sweet terpene or sweet-citrus is more appropriate. “The peroxide breakdown products of terpenes are responsible for the spoiled citrus oil off-notes. Folding of citrus oils allays this instability problem.” “One-hundred pounds of an oil is concentrated ten times by distilling off 90 pounds of terpenes. This resultant ten pounds is known as a ten-fold oil, and by virtue of the removal of this, a significant amount of terpenes, the resultant ten-fold oil is a more stable, more soluble and more potent flavor.” The terpenes are known for their juicy citrus flavor vs. the aldehydes (discussed later) which represent flavors characteristics of citrus rind.
Aromatic Sweet and Spicy compounds are responsible for the aromas of the spices as the name implies. Although similar in structure to the terpenoids, these differ chemically, in that they usually contain one or more complex oxygenated (oxygen containing) molecular groups. Note again, the confusion with the terminology “sweet”. As stated before, sweet-fruity, sweet-spicy (both olfactory) and sugary-sweet (tongue) are descriptions which are far more appropriate. When we encounter this blend, it is the first time that we are smelling a true flavor blend. Notice when smelling this blend that the flavor profile will not change too much during the evaporation of the blend off of the blotter. This is typical of a well-rounded, sophisticated (or “tightly blended”) flavor profile. A sophisticated (adult) type of flavor - in this case, a Benedictine-type flavor, is the opposite of a more “loosely blended”, less sophisticated, children-oriented mix. A flavor which is a simple mixture, one with off-notes, and flavor “peaks and valleys” or a flavor which does not perform well in a specific system, is called a disjointed flavor (see diagram - flavor curve). “Remember, depending on the systems and processing conditions, it is not unlikely that a well-blended flavor profile can become disjointed when used in a different systems or when processed differently. The flavorist can often compensate for this effect once the final flavored product is tasted and these discrepancies are then perceived and the problem is able to be identified.”
Pungent floral odors are the bases of more perfume fragrances and make up the background and trace “natural nuances” of most flavors. These are truly the “perfumy” odors. Contained also herein are the aliphatic aldehydes responsible for the rindy citrus characters. Because of their strength and their association with “clean smells” when used at low levels, these compounds are often used in soaps and detergents. Also included are acyclic monoterpene alcohols.
Sugars are cyclized polyalcohols, e.g., compounds with many alcohol groups (an oxygen and hydrogen). Upon heating, “sugars can either break down themselves or react with other components in a system (amino acids, proteins, etc. - Maillard Reaction) to form a host of products. Typically, the sugars found in food systems form brown-type aromas when they are heated, browned, toasted, etc. The Maillard Reaction, a reaction between sugars and amino acids (or proteins) is an example of what is called non-enzymatic browning.” ENZYMATIC BROWNING or table browning is when a banana or apple is bruised and then, the fruit then turns brown at the point of impact. This is a self-induced enzymatic breakdown.” Compounds which impart a brown flavor include: ethyl vanillin, ethyl maltol, pyrazines, thiazoles, furans.
Besides being a normal ingredient in vanilla, vanillin can also be formed when lignin, the binding stuff of wood and a by-product of the paper industry is oxidized or burned. This is why often when someone enters a lab that has been using vanillin, comments like “I smell wood burning” are typical. Maltol (a malt-like compound) is another of the brown compounds formed through fermentation and Maillard Browning.
An extension of the brown category is a subgroup - the phenols. When compounds are more drastically oxidized, or burned, they can form simpler phenols. The flavor of these compounds (some describe them as black flavors) include the char-like, road tar-like or smoky-flavor characteristics.
The brown group imparts a SWEET brown flavor, again cautioning against the term sweet as used alone. When dipped into the blend that is representative of this group, the blotter first smells like TOASTED coconut, marshmallow, cotton candy, or vanilla, and then the blotter begins to smell smoky and burnt.
Woodiness is a dry, heavy characteristic and is obviously typical of the odor of wood. These compounds are related to the aromatic terpenoids in structure. However, they are usually more complex molecules and are typically larger in molecular weight. Berries are usually distinguished from the other fruits; citrus, grapes, melons, and pit-fruits, by virtue of the trace woody nuances (pitty, seedy flavors) contained therein. When dipped into this mixture, the blotter smells first like raspberry due to the presence of ionone. After a short time the profile changes to a cedar-like odor. This is due to the presence of cedrol, the active constituent in oil of Cedarwood.
The Lactonic group can impart a creamy, milky, even coconutty odor. These compounds are very important factors in dairy flavors, and important as flavorants in certain fruits like peach and apricot (also the tropical fruits like papaya, passionfruit, and mango). When dipped into this blend, the blotter first smells like creamy butter, WHITE MEAT coconut, then peach. Lactones are extremely strong compounds and need to be used judiciously.
The sulfury group contains compounds whose odors vary from those similar to sewer gas and rotting vegetables to animal-like odors. Although these compounds are definitely repulsive at higher levels, when used at the trace levels at which they are found in nature, they are very important in defining a certain otherwise unattainable “naturalness of character”. This is also a group where we can conveniently include the odors of the musks, as well as the odors described as meaty and animal-like.
When dipped into this blend, the blotter will first smell like onion and garlic, and then like a mixture of potato and vegetable. These compounds can typically come from internal enzyme conversion of precursors that are contained in the food itself (mustard, onion). They also can be formed via a breakdown or a reaction of sulfur containing amino acids like cysteine, (eggs) and methionine (potatoes).
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