Wine Structure

On the WSET Level 3 SAT, a wine's structure is assessed in the palate section. WSET's Level 4 Diploma tasting guide (Issue 13, August 2018) names a wine's structural components as elements such as sugar, acidity, tannin and alcohol, and notes that different tasters have different levels of sensitivity to them. Its guidance is that tasters 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 same guide says the words used to describe aromas and flavours are more subjective, with more flexibility in how exam marks are awarded.

• WSET's Diploma tasting guide gives sugar, acidity, tannin and alcohol as 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 (WSET, 2018)
• Aroma and flavour descriptors are treated as more subjective, with more flexibility in how exam marks are awarded

WSET's Diploma tasting guide describes an assessment of quality as 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: the guide lists concentration, acidity, tannin and the development of aroma and flavour characteristics among the factors in 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. A 2023 WSET blog post on pairing calls salt, acidity and fat in food 'the magic triangle', saying that 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 (WSET, 2018)
• 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
• WSET's 2023 pairing post gives a salty rib eye steak with a tannic and acidic Barolo as a classic match, the salt and fat smoothing the tannins

Sweetness is mainly the taste of sugar present in the wine, though WSET notes that 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, per a Washington State University extension primer (originally published 2008)
• In WSET's Diploma tasting guide the tannin headings apply only to red wines, with no tannin marks for white or rosé wines; the guide notes some skin-contact whites, oaky whites and rosés can have very low levels of tannin
• Alcohol bands in WSET's Diploma guide (2018): 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

WSET's method is to rate each component on its own scale and pick one entry: the Level 3 SAT tells students that where entries are separated by a hyphen they must select one and only one. For acidity, the more the mouth waters, and the longer it waters, the higher the acid level; WSET notes that a dehydrated taster's mouth waters less, and that 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 WSET suggests checking 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 (WSET, 2026)
• 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, it says, 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. The guide suggests asking 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. WSET's 2026 guide to acidity gives a Mosel example: 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, per WSET, 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
• WSET describes a well-made Sauternes as searingly acidic yet coming 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

WSET's 2023 post on ageing says the vast majority of wines sold are designed for immediate consumption, and that 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. Its 2026 acidity guide adds that acids act as natural preservatives, allowing fine wines to age for a decade or more. As wines age, WSET's Diploma guide notes, 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; a Washington State University extension primer (originally published 2008) says 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. WSET lists Barolo, Vintage Champagne and Grand Cru Classé Bordeaux among wines where ageing is important to the style.

• The vast majority of wines sold are designed for immediate consumption (WSET, 2023)
• 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 (WSET, 2018)
• 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 2026-09-29