Taste Compounds, Chemistry, Anatomy & physiology of the sense of Taste in Wine continues..
Taste compounds- tastants, have smaller molecules than those of odors and, unlike odors, must be water-soluble (hydrophilic) to cause sensation. Fortunately wine is liquid and the taste components in it are already dissolved in the product. Our oral cavity senses taste and touch.
Some interpretations of the sense of touch, like: Austerity of tannins, or burning of overpowering Alcohol, oiliness of glycerin etc. that have texture (affecting the touch sensation) and other physical features such as temperature, all related to the sense of touch are many times confused with the actual sense of taste. While there may be many aroma nuances within the wine Aromas categories, as arranged on the Aroma wheel, there are only four tastes considered in wine: salty, sour, sweet and bitter.
(The section below, aided by: Taste: Compiled by Tim Jacob, Cardiff University, UK : http://www.cf.ac.uk/biosi/staffinfo/jacob/index.html )
Salty tastes, very seldom are present in wine because most vine rootstocks are known to restrict the uptake of salt (maybe in Jerez and some western Australian wines). But minerality can sometimes be mistaken as salty. Salty is the most common of tastes, these come from sodium chloride (table salt), sodium nitrite, sodium bicarbonate (as in baked foods), and sodium benzoate (in various beverages). Salt (sodium chloride (Na+ Cl-). Affect the taste receptors by Na+ ions entering the receptor cells via Na-channels. The entry of Na+ causes cell depolarization, transmitter release occurs and results in increased firing in the primary afferent nerve, thus salty sensation is interpreted in the brain. But as mentioned there are very few wines that are salty or give rise to real salty sensation.
Sour tastes come from acids citric acids in citrus fruits, malic acid in apples peach or pears, tartaric acid in wine and lactic acid in milk products.Sour taste is acid which are protons: (H+). Some new evidence suggests that there is an acid-sensing channel. This channel is from the transient receptor potential channel (TRP) family and is a non-selective channel. The activity is gated by pH (H+ ion concentration). Apart from wine, acids are found in a wide variety of fruits, vegetables and foods products such as baked, soft drinks, sweets, jams, jellies, milk products, processed meats and even oils.
Sweet tastes comes from sugars, primarily sucrose and others like, glucose, fructose or lactose There are special proteins in the taste receptor membrane that bind glucose and other carbohydrates like sucrose and fructose that activate intracellular messengers, that transmit impulses through the primary afferent nerve to the brain, sweetness is sensed
Bitter tastes come from alkaloids, such as contained in coffee and quinine (tonic water). Bitter substances bind to T2R receptors activating the G-protein and causing activation of PLC. The elevated Ca2+ causes transmitter release and this sends electrical messages of bitterness to the brain.
Although taste buds were noted to be of different sizes and shapes, depending upon their location, subsequent investigation proved that all of them contain the same kinds of taste receptor cells (papillae) that supply the sensations of taste. The entire top surface of the tongue can sense all of the various tastes.
Taste receptor cells do not have an axon. Information is relayed to terminals of sensory fibers by transmitter. These fibers arise from the ganglion cells of the cranial nerves Vll (facial) – a branch called the Chorda Tympani and cranial nerve lX (glossopharyngeal).
We already established that taste is mainly smell (a combination we describe as Flavour). Without smell we cannot tell the difference between food or drink products. After all orange is sweet and sour with orange smell and melon is also sweet and sour but with melon smell etc. same goes with red or white wines.
When a tasty product enters the mouth, its chemicals are dissolved by the saliva, and the free-floating molecules enter the taste bud through a pore in its center. If the molecule binds to the tip of a receptor cell, it will excite that cell into issuing a series of chemical and electrical signals. For example, sweet and some bitter taste stimuli activate a chemical messenger known as Gustducin, from the G-family of proteins. That send the data relayed to the brain (to the gustatory cortex) and a sensation of “sweet” is interpreted in the brain/mouth.
Salty and sour molecules do not require the receptor tips. Na Ions enter the taste cells directly through special channels in their walls.
But the “taste of wine” is not governed solely by the 4 basic taste, Minerals Tannins and Alcohol are also important factors in what we call: “the taste of wine”. Sweetness and alcohol are round in their “touch” while acidity and tannins are harsh or sharp cornered, rigorous to the touch (austere). When the rounded and sharp edge components balance each other to a “new” completion, a wine can be described as balanced.
Sweetness In wine most the sugars turn to alcohol during fermentation. Wines may have some residual sugar, and according to the amount of sugar in Grams per litter wines may vary from Brut (totalt dry) to dry up to 4 g/l, medium dry up to 12 g/l, medium sweet up to 45 g/l, to swee more than 45 g/l. In the wine industry sugar is measure either by portable brix meters in the vineyard or others at the winery .Degrees Brix (°Bx) is the sugar content of an aqueous solution. One degree Brix is 1 gram of sucrose in 100 grams of solution. As the wine’s alcohol level depends on the sugar content (brix multiplied by 5.5= the future wine alcohol level). A measurement of the sugar content of grapes, must and wine, indicating the degree of the grapes’ ripeness (sugar level) at harvest. Most wine grapes are harvested at a level of between 22 and 25 Brix depending on the grape variety and winemaker preferences (apart from climate ripeness restrictions)
Acidity. Wines contain mainly tartaric acid (from the grapes); which gives the wine a fresh fruity touch on the palate and tongue, sort of a “crisp” feel, mainly felt on the sides of the tongue. Wines with insufficient acidity may taste dull or even jammy or “tired”. In white wines, which have less tannin than reds, acidity is important to the body and feel of the wine.
Bitterness in wine is elicited primarily by flavonoid phenols in red wines, which are bitter and astringent, and by ethanol. Monomeric flavonoid phenols are primarily bitter. The difference between red and white wine phenol monomers produces a significant difference in brain perception of bitterness. Ethanol enhances bitterness intensity and duration, whereas varying wine pH has little or no effect on the perceived bitterness. (from Bitterness in wine by Noble AC. Physiol Behav. 1994 Dec;56(6):1251-5)
Tannins – bitterness in wine is mainly attributed to Tannins, are a family of natural organic compounds: flavonoid phenols that are found in grape skins, seeds, and stems. Aging wine in oak barrels transfers oak tannin into the juice which affects the touch and flavour. Tannins are also act as natural preservative to wine and introduce important antioxidants to our body. They take a major part in establishing wine structure and texture. The longer the grape skin contact with the fermenting wine, or in relation the crushing method of grapes, tannins concentration is affected especially in Red wine where it affects taste, touch sensation At times Tannins may feel a bit overpowering, that leaves our mouth dry. and the depth of colour. Tannic wines affect the touch sensation in the mouth and back of the throat. Tannins also contribute at times a bitter aftertaste.
Alcohol – Alcohol is another important component of the wine taste. It may contribute a burning sensation on the palate and throat when excessive, but It has a major role in achieving the overall balance of wine by softening the “edge” of over acidic or tannic wines. Alcohol affects the feel of “body” to wines. A wine with high alcoholic content will always feel full bodied.
Minerals – Soil minerals travel into the grape with water. Grapes, must and wine contain dissolved non-organic salts. These salts are local soil minerals or metal elements, and occur naturally in grapes, minerals attach to berry surfaces as a result of vineyard treatment methods, and enter the wine during the wine making process. The concentration of potassium, nitrogen, phosphorus, sulfur, magnesium and calcium can range from 200 to 2,000 mg/l in grape juice. Potassium is an important factor in defining wine pH and tartrate stability. Its concentration in wine ranges from 200-2000 mg/L High level of potassium in wine has great nutritional values. (from http://waterhouse.ucdavis.edu/whats-in-wine/minerals). Minerals are often felt stronger in white wines grown on chalky soil, described in French as: goût de fossile (the taste of Fossils), sensed in Chablis and Bourgogne whites.
Change of taste in aging wines
Oxidation is the most important part of wine maturation. These changes include the change in colour of red to brick brown red during aging, loss of primary flavour varietal character and the development of secondary and tertiary aromas. These changes appear in white and red wines, but they are more noticeable in white wine. The rate of oxidation depends on pH, temperature, concentration of dissolved oxygen, and the phenolic composition. Oxidation is faster in lower acidity and high temperature conditions, in the barrel and later in the bottle. Oxidation also depends on the phenolic composition of the wine.
Careful storage of aging wines, will help wines become smoother, rounder with well incorporated tannins, as through polymerization of phenolic compounds causing them to become less bitter and reduction in acidity which should not affect the fruitiness of the wine. Further polymerization of phenols, enlarges their molecular size causing them to precipitate and sink as sediments the bottle. This leads to a smoother wine with reduced astringency and a rounder taste. The rest is really down to your “taste” or “flavour” vocabulary, which in wine is governed by association: cinnamon, coffee, chocolate, tobacco, saddle soap, vanilla, toasted bread, tarte Tatin etc. are all picked from past exposure and association.
All of these and some more… contribute to what is called the TASTE OF WINE, and if you got all the way to here, You do deserve a wine that tastes good whatever that means, after all taste is a personal preference.
Anatomy and physiology of smell in wine tasting.
The sense of Smell in wine tasting
Two of our five senses respond to the chemical stimuli from our surroundings: taste and smell. Both depend on chemical interaction, known as chemoreception. Taste is: contact chemoreception, because to sensing the taste of anything requires contact with it. Smell is: remote chemoreception, it is airborne, and can be sensed from a distance.(from The Sense of Smell (Brief Overview for Primary/Secondary Grade Students) http://www.youtube.com/watch?v=dIDBG-UPRUI
In 1990 BBC books published a small (soft cover) book, by Jilly Goolden, titled “The Taste of WINE“, for me it was one of the basic ABC’s to wine tasting. It meticulously described all the “Smells of wine”, not TASTE (divided by country of origin, grape variety, local blends etc.). Semantically, it follows the title of the reference book by Emile Peynaud: The Taste of Wine: The Art Science of Wine Appreciation (1984). Both books are titled mistakenly: The taste of wine. But it is by the aromas of wine (the sense of smell) that wine is “tasted”. It occurs mainly by accumulating information from smelling the wine in the glass before tasting and retro-nasally through the back of the mouth as the wine is swirled in the mouth, It is here that vapors of wine smells travel via the Nasopharynx to the olfactory bulb, and finally translated in the form of flavour by the brain. The human tongue (sense of taste) is limited to the primary tastes perceived by taste receptors on the tongue: sour, bitter, salty, sweet and savory (Umami). The wide array of fruit, earthy, floral, herbal, mineral and woody flavours perceived in wine derive from aroma notes which are interpreted in our brain through chemical information obtained by the primary receptor cells in the olfactory membrane.
.In professional wine tasting, a distinction is made between wine odors: “aromas” and “bouquet“.
The term Bouquet refers to the smells that arise from the chemical reactions of fermentation and aging of the wine in the bottle as part of the wine aging process, these are more complex kind of smells, combined together to induce an odor from our memory bank of smells (ground coffee, cigar box, leather, Tarte tatin, toasted bread, compost, caramel, toffee, mint etc.)
Apart maybe from wines made from the Muscat grape no wine smells like the juice of the grapes variety it is made from. Aroma refers to the smells unique to a certain grape variety, and is most readily demonstrated in varietal wines–such as Raspberries and blackcurrants with Cabernet Sauvignon, exotic fruits and canned Leeches with Gewürztraminer or Gooseberries and freshly cut grass in Sauvignon Blanc. These are smells that are commonly associated with a young wine.
As wine ages chemical reactions between the acids, sugars, alcohols and phenolic compounds, create “new smells” that are known as a wine’s bouquet. These can include honey in an aged Sauternes or mushrooms even truffles in a Pinot noir, and others listed above. The term bouquet can also be expanded to include the smells derived from fermentation and exposure to oak. Wine aromas are sub-divided into three categories-primary, secondary and tertiary aromas.
Primary aromas are those specific to the grape variety itself. Secondary aromas are those derived from alcoholic fermentation and oak aging. Tertiary aromas are those that develop through bottled aging.
Wine contains volatile and non-volatile compounds that contribute to the overall wine aroma. The majority of volatile compounds responsible for aroma combine with sugars in the wine to form odorless glycosides. Through the process of hydrolysis, caused by enzymes or acids in the wine, the odorless compounds revert into an aromatic form, thus the act of tasting wine is essentially an act of smelling vaporized aroma compounds
Of the human senses, the sense of smell is the most precise, with high sensitivity to minute amount of odorant. It is also the most fragile. Most of us have experienced detecting an aroma of bread baking, even from a long distance and certainly in the bakery, yet after a fairly short but continuous exposure of just a few minutes, that same smell is less noticeable. This “fatigue” is really an accommodation process of the sense of smell by means of sensory adaptation and occurs in other senses as well.
Since olfaction is connected directly to the Limbic system in our brain that supports a variety of functions, including emotion, creativity, long-term memory, and olfaction. Being primarily responsible for our emotional life, the formation of memories and smells in the same brain center facilitates connection of certain emotions that were evoked with a certain odor “background” a memory of that smell will be unconsciously related to an emotion. A connection between emotion memory and smell is created in our brain. The memory/olfaction connection plays a major role in the ability to relate (by association) wine odors to groups of smells fruity floral vegetal etc. which is a basic requirement in wine tasting. In fact of all our senses, the sense of smell is the most intimately connected with the brain.
The amount of odors in wine and their inner intricacies present a huge vocabulary from which to choose when coming to describe a wine. Ann C. Noble of University of California, Davis, formulated an aroma aid called the “Aroma Wheel”. It divides the various wine aromas to groups and sub groups within them covering the most commonly aromas encountered in table wines this was a means to try and “standardize” terms used to describe wines to a point that wine tasters, wine journalist, wine novices and readers of wine articles will “know” what was meant by a certain description:
The Aroma Wheel provides a visual graphic of the different categories and aroma components that one can encounter in wine.
The wheel breaks down wine aromas into 12 basic categories and then sub-divides them into different aromas that fit those main categories:
Fruity – Aromas like blackcurrant, apricot, apples and plums
Floral – Aromas like rose, acacia, or Jasmine
Spicy – Aromas like cloves, cinnamon or anise
Microbiological – Aromas like yeast and lactic acid
Nutty – Aromas like pine nuts walnut and hazelnut
Caramelized – Aromas like butterscotch and molasses
Woody – Aromas often imparted by oak like vanilla and coffee
Earthy – Aromas such as mushroom compost and mildew
Chemical – Includes aromas like sulfur and petroleum or nail varnish
Pungent – Aromas like alcohol and vinegar
Oxidized – Aromas like Sherry or acetaldehyde
Aroma Wheel: property of Aromaster wine aroma kits http://www.aromaster.com/product/wine-aroma-wheel/
A drawback of the wheel is that it does not contain terms used to describe the sense of touch on the palate, like texture or astringency, which affect the overall “tasting experience” and are a major factor in determining a wine’s quality, balance.
Prior to tasting the wine, a good swirl of the glass releases wine odorants into the glass bowl. Some glasses are specifically designed to enhance aromatic qualities and characters of different wines, these assist in capturing more aromatic compounds within the glass for the taster/sniffer, to detect. Wines served at warmer temperature will be more aromatic than wine served cooler due to heat’s ability to increase the volatility of aromatic compounds in the wine. Swirling aerates, the wine and increases available surface area, increasing the amount of volatilized aromatic molecules. Some subtle odors can be hidden by a more dominant smell that arise after swirling, so most professional tasters will sniff the wine briefly first before swirling.
The deeper our nose is stuck inside the glass, the greater the chance to capture the specific wine aromas. Our nose can detect and distinguish between thousands of different smells, which increase by means of training through exposure.
When wine is sipped, it is warmed in the mouth and mixes with saliva to vaporize the volatile aroma compounds. These compounds are then inhaled “retro-nasally” through the back of the mouth to where it is received by the millions of nerve receptor cells in the olfactory bulb. An average human can be trained to distinguish between thousands of smells but can usually name only a handful at a time when presented with a wide variety of aromas. Professional wine tasters will use their vast “library” of memorized aromas, for those with a lesser collection of memorized odors a visual aid like the aroma wheel.
Detecting an aroma is only part of wine tasting. The next step is to describe or communicate what that aroma is verbally. In this step subjective nature of wine tasting is most prominent. Different individuals have their own way of describing familiar scents and aromas based on their unique smell experiences, memories and “smell vocabulary”. Furthermore, there are varying levels of sensitivity and recognition thresholds among humans of some aromatic compounds. This is why one taster may describe different aromas and flavors from another taster sampling the very same wine.
In 1981, as a result of his research into vocabulary used to describe wine, Jean Lenoir created Le Nez du Vin®, a unique and learned combination of written works and collection of bottled aromas covering a large array of odors which form a part of the scents of wine.
“Le Nez du vin is a The 54 Aroma Master Kit has been the reference for wine aromas vocabulary. Our sense of smell is very delicate and highly sensitive. Practice through daily training allows us to recognize and identify the 54 aromas most commonly present in wine; thus, improving our appreciation and enjoyment of wine. These are the typical aromas found in red and white wine (including Champagne) from France and around the world. They give us an indication of the wine’s origin, the grape variety as well as the vineyard, the winemaking techniques used and the aging conditions. Memorizing these aromas provides an accurate and coherent vocabulary to further stimulate our appreciation of fine wines”
The 54 Aromas of Le Nez Du Vin are:
23 Fruit Aromas, 6 Floral Aromas, 10 Vegetal Aromas, 5 Spices, 3 Animal Aromas and 7 Grilled Aromas (full list could be found in: http://www.winearomas.com/master_kit.html
“It is widely accepted that sensory interactions can, and do, occur during wine consumption. To this concern, many studies have dealt with aroma-taste interactions which have been attributed to physicochemical interactions in the product itself, interactions at the receptor level or cognitive interactions. Although the understanding of these interactions has grown during the years and it has been demonstrated that they are strongly product-dependent, investigations have seldom gone beyond that of model solutions with a reduced number of components (volatile and/or nonvolatile molecules). Recently some investigations carried out in this field have been conducted with more complex matrices in an attempt to simulate interactions in real wine samples. The aim of this chapter is to review these latest advances in the research of wine sensory interactions, and to highlight the magnitude, relative importance and qualitative nature of such sensory effects.” (From: Sensory Interactions in Wine: Effect Of Nonvolatile Molecules on Wine Aroma and Volatiles on Taste/Astringency Perception Authors: (María-Pilar Sáenz-Navajas, Eva Campo, Dominique Valentin, Purificación Fernández-Zurbano, Vicente Ferreira).
The “correct” scent of wine can quite easily be reached at the winery level but the quality of wine starts at the flavour’s level which is a combination of taste and smell add to those the sense of touch on our palate and the balance of the wine can be judged to give a complete view of the wine’s quality.
Next post of the sense of taste continues “our” journey through the symphony of senses in relation to wine tasting.