Wine Structure

On the WSET Level 3 SAT, a wine's structure is assessed in the palate section. A wine's structural components are elements such as sugar, acidity, tannin and alcohol, and different tasters have different levels of sensitivity to them. The WSET Level 4 Diploma tasting guide (Issue 13, August 2018) expects tasters to calibrate their palates against their educators so they can classify each structural component with SAT terms such as 'high', 'medium' or 'low', relative to the world of wines generally. The words used to describe aromas and flavours are more subjective, with more flexibility in how exam marks are awarded.

• Sugar, acidity, tannin and alcohol are examples of a wine's structural components
• The Wine SAT relies on three- or five-point scales to describe the structural components of a wine
• Aroma and flavour descriptors are treated as more subjective, with more flexibility in how exam marks are awarded

An assessment of quality is an overall impression based on the sum of a wine's structural components (acidity, tannin, alcohol, etc.) and its flavour and aroma characteristics. Structure also feeds the judgment on ageing: concentration, acidity, tannin and the development of aroma and flavour characteristics are among the factors the Wine SAT lists for a wine's readiness for drinking and potential for ageing. For food pairing, the WSET Level 3 specification (Issue 2, 2022) lists sweetness, acidity, tannins (oak), complexity, fruitiness and alcohol level as the wine considerations. WSET's 2023 pairing guidance calls salt, acidity and fat in food 'the magic triangle': having these on the palate before an acidic, astringent and tannic wine will help soften it.

• Quality assessment rests on the sum of the structural components plus the flavour and aroma characteristics
• Concentration, acidity, tannin and the development of aroma and flavour characteristics are among the ageing factors the Wine SAT lists
• WSET Level 3 wine considerations for food pairing: sweetness, acidity, tannins (oak), complexity, fruitiness, alcohol level
• A salty rib eye steak with a tannic and acidic Barolo is a classic match: the salt and fat on the steak smooth the tannins

Sweetness is mainly the taste of sugar present in the wine, though alcohol and glycerol can add a perception of sweetness too; the Level 3 SAT scale runs dry, off-dry, medium-dry, medium-sweet, sweet and luscious. Acids cause a sharp, tingling sensation, for most people strongest at the sides of the tongue, and make the mouth water; wines with low acidity feel broad, soft or even flabby, while wines with high acidity are notably crisp, zesty and mouth-watering. Tannins bind to proteins in saliva, causing a drying sensation; they contribute to the texture of a wine and can also have a bitter taste. Alcohol is detected mainly through the sense of touch, and at high levels it can give a hot, burning sensation. Body is the perception of a wine's weight on the palate, its fullness. The finish is the collection of sensations on the palate after the wine has been swallowed or spat out.

• Tannin sources: condensed tannins are found in the grape's skin and seed, while the hydrolyzable tannins in wine are ellagitannins derived from oak barrels
• The Diploma tannin headings apply only to red wines, with no tannin marks for white or rosé wines in the exams; some skin-contact whites, oaky whites and rosés can have very low levels of tannin
• Diploma alcohol bands: below 11% abv low, 11% to 11.9% medium(-), 12% to 12.9% medium, 13% to 13.9% medium(+), 14% or above high; for fortified wines the medium level is 17% to 19% abv
• Body: for most wines alcohol is the main factor; sugar and grape extract add to body, whereas high acidity makes a wine feel lighter
• Mousse, the feel of a sparkling wine's bubbles, has its own line on the Level 3 SAT, rated delicate, creamy or aggressive

Each component is rated on its own scale: on the Level 3 SAT, where entries are separated by a hyphen, students must select one and only one. For acidity, the more the mouth waters, and the longer it waters, the higher the acid level; a dehydrated taster's mouth waters less, and high sweetness can lessen the perception of acidity while the mouth-watering effect remains a reliable guide. The drying effect of tannin is felt most clearly on the gums above the front teeth. The burning sensation of alcohol can be confused with the tingling of acidity, so check whether the wine is also mouth-watering (acidity) or feels thick and viscous (alcohol), remembering it may be high in both. For the finish, only the persistence of positive sensations counts: if a bitterness lingers but the fruit impressions disappear quickly, the finish is short.

• Drink plenty of water before tasting: dehydration suppresses salivation, and acidity may then be underestimated
• In a sweet wine the acidity appears less obvious than in a dry wine, but the mouth-watering effect remains
• Make sure some wine reaches the gums above the front teeth to read tannin
• Mouth-watering points to acidity; a thick, viscous feel points to alcohol; a wine may be high in both
• A basic quality wine's pleasant flavours often disappear within a few seconds (short finish); a very fine wine's can last a minute or more (long)

WSET's Diploma tasting guide calls a wine's overall balance and/or integration perhaps the most reliable indicator of quality. In high-quality wines an impression of sweetness on the palate (fruit character and/or residual sugar) is balanced by an impression of sourness (acidity or tannic astringency). With too little fruit character or residual sugar a wine will seem unbalanced, austere and thin; with too little acid or tannin it will seem flabby or unstructured. It helps to ask whether a particular feature stands out on the palate: marked acidity may complement the depth of fruit, freshening the palate, whereas alcohol that dominates can result in a hot, burning finish. In the Mosel, a bone-dry Trocken Riesling can show bracing acidity, while a sweeter Spätlese from the same region could have a similar level of acidity, but its residual sugar changes how that acidity is perceived. In WSET exams it is not sufficient to call a wine simply 'balanced'; the taster must explain what is balanced with what.

• In high-quality wines an impression of sweetness (fruit character or residual sugar) is balanced by an impression of sourness (acidity or tannic astringency)
• Too little fruit or sugar reads as austere and thin; too little acid or tannin reads as flabby or unstructured
• A well-made Sauternes is searingly acidic yet comes across as luscious rather than sharp, because sugar and acid work together
• Among WSET's quality categories, a 'good' wine typically has well balanced fruit, sugar, acid and tannin

The vast majority of wines sold are designed for immediate consumption, and wines able to age tend to have two things in common: plenty of flavour intensity and natural preservative qualities such as high acidity or high tannin levels. Acids act as natural preservatives, allowing fine wines to age for a decade or more. As wines age, any tannins soften, alcohol levels do not change, and acid and sugar levels change very little. WSET attributes the softer, smoother taste of aged red tannins to a process called polymerisation, while a Washington State University extension primer (originally published 2008) holds that the precise mechanism for the loss of astringency during ageing has yet to be proven. A mainly fruity wine with a light acid or tannin structure almost certainly belongs in the SAT's 'drink now: not suitable for ageing or further ageing' category, while a very firm structure of acid or tannin with a high level of flavour concentration may benefit from ageing. Barolo, Vintage Champagne and Grand Cru Classé Bordeaux are among the wines where ageing is important to the style.

• The vast majority of wines sold are designed for immediate consumption
• Ageworthy wines tend to combine plenty of flavour intensity with natural preservatives such as high acidity or high tannin
• With age, tannins soften, alcohol is unchanged, and acid and sugar change very little
• Mainly fruity with a light acid or tannin structure: drink now; very firm acid or tannin plus high concentration: may benefit from ageing

Primary sources: https://www.wsetglobal.com/media/11766/wset_l3wines_sat_en_may2022_issue2.pdf, https://www.wsetglobal.com/media/11731/wset_l3wines_specification_en_highres_may2022_issue2.pdf, https://www.wsetglobal.com/media/6714/wset_l4diploma_cag_tasting_en_aug2018.pdf, https://www.wsetglobal.com/knowledge-centre/blog/2026/understanding-acidity-in-wine, https://www.wsetglobal.com/knowledge-centre/blog/2023/march/21/why-do-we-age-wine, https://www.wsetglobal.com/knowledge-centre/blog/2023/july/13/four-rules-to-masterful-food-and-wine-pairing, https://wine.wsu.edu/extension/grape-and-wine-phenolics/. Last verified 2026-10-05