FNH 330 L1 Wine Composition and Sensory Evaluation

What is the formal scientific definition of wine, and why does that definition matter?

Wine is defined as an alcoholic beverage obtained by the fermentation of juice or must from grapes

What are the 6 major chemical components of wine, what sensory quality does each contribute, and what is the general concentration range for each?

• Water — 78-92% — the dominant solvent; carries all other components

• Ethanol (alcohol) — 7-21% — contributes body, warmth/"heat," and mouth-coating sensation; range spans from off-dry table wines (~7-9%) through dry table wines (~11-15%) to fortified wines (~17-21%)

• Acids — 0.2-1.0% — responsible for sourness/tartness; critical for wine structure, preservation, and microbial stability

• Sugars — 0.1-10+% — responsible for sweetness; residual sugar left after fermentation; trace in dry wines, high in dessert wines

• Phenolic compounds — 0.05-0.3% — responsible for bitterness and astringency; includes tannins, pigments, and health-associated compounds (e.g. resveratrol)

• Volatile compounds (aromas & flavours) — trace levels only (parts per million or billion) — responsible for all the complex aromas and flavours that make wine interesting; there are 200-1,000+ such compounds

• Key insight: even though aromas are at trace levels, they have the greatest impact on wine complexity and enjoyment — a tiny amount of a volatile compound can completely define a wine's character

How do the major components of wine differ between a dry white wine (e.g. Sauvignon Blanc) and a dry red wine (e.g. Cabernet Sauvignon)?

What drives these differences?

• Ethanol: dry white ~12.5%, dry red ~14% — reds typically have higher alcohol because they are made from riper grapes with more sugar to ferment

• Phenolics: dry white ~0.1%, dry red ~0.3% — reds are THREE TIMES HIGHER because red winemaking involves skin contact during fermentation; grape skins contain most of the tannins and pigments

• Practical consequence: reds taste more tannic, bitter, and astringent; whites taste fresher and more acidic — all explained by these compositional differences

• The phenolic difference is also why red wines are more commonly associated with health benefits (antioxidants) and why they age better (tannins preserve)

What are phenolic compounds in wine, what are the two main classes, and why are they important to both taste and wine quality?

• Phenolic compounds are a large family of chemical compounds that contain one or more hydroxyl groups attached to a benzene ring

• They are responsible for the bitter and astringent qualities of wine and are found at 0.05-0.3% concentration

• Class 1 — Flavonoids: make up ~90% of all wine phenolics; include anthocyanins, flavonols, and tannins

• Class 2 — Non-flavonoids: the remaining ~10%; include stilbenes and ellagitannins

• Reds have ~3x more phenolics than whites because phenolics are concentrated in grape skins, and red winemaking involves prolonged skin contact during fermentation

Phenolics affect colour, bitterness, astringency, aging potential, and are linked to antioxidant health effects

Explain the flavonoid subgroup of phenolics: what are anthocyanins, flavonols, and grape tannins, and what role does each play?

• Anthocyanins — red/purple pigments found in grape skins of red varieties. They are NOT present in white wines (which is why whites are not red)

• Flavonols — yellow pigments; present in both red and white wines but especially important in whites; contribute to the straw and golden hues of white wine

• Grape tannins — astringent and bitter polyphenolic compounds; they react with and precipitate proteins; this is the key mechanism of astringency

Tannins bind to salivary proteins in your mouth, removing the lubricating proteins and causing the dry, rough, puckering sensation

What are non-flavonoid phenolics in wine, and what are the two most important examples?

• Non-flavonoids make up ~10% of wine phenolics and are structurally different from flavonoids

• Stilbenes — the most famous example is resveratrol

• Ellagitannins — also called "wood tannins" because they come from oak barrels during aging, NOT from the grapes themselves; they also cause astringency

What are volatile compounds in wine, and why do they matter?

• Volatile compounds are present in wine at trace concentrations (parts per million or billion) — they are the 200-1,000+ compounds responsible for all aromas and flavours

They matter enormously: even at tiny concentrations, they completely define the character of a wine and are the primary driver of wine quality perception

• They are NOT added to wine — aromas arise naturally from the grapes, fermentation process, and processing

What are the 5 classes of volatile compounds and what aromas do they contribute?

• Class 1 — Aldehydes: e.g. hexanal; vegetal and green apple vibes

• Class 2 — Terpenes: e.g. linalool; give floral, minty, citrusy aromas

• Class 3 — Norisoprenoids: e.g. β-damascenone; give leafy, fruity, petrol aromas

• Class 4 — Methoxypyrazines: e.g. 3-isobutyl-2-methoxypyrazine; give green bell pepper and asparagus aromas

— The multicoloured Asian ladybeetle produces the same methoxypyrazine compound when accidentally harvested with grapes, giving wine an unpleasant green pepper/asparagus off-flavour

• Class 5 — Thiols: e.g. 3-mercaptohexan-1-ol; give grapefruit and guava aromas

Where do aromas in wine come from — what are the three sources, and what three factors determine which aromas a wine will have?

Source 1 — Grape skins (primarily) and pulp (to a lesser extent): the major source of varietal aromas that define the grape variety's character

Source 2 — Fermentation: yeast convert sugars to alcohol and CO2, but also produce many aroma compounds as byproducts (e.g. esters giving fruity aromas, higher alcohols, fatty acids)

Source 3 — Processing: oak barrel aging adds vanilla, spice, toast, and wood tannin aromas; malolactic fermentation (where bacteria convert malic acid to lactic acid) can add a buttery/creamy note (diacetyl)

• Factor 1 — Grape variety: each variety has a characteristic aroma profile due to its unique mix of volatile compounds

• Factor 2 — Ripeness of the grape: unripe grapes have more vegetal/herbaceous notes; riper grapes develop more fruit aromas; overripe grapes develop jam, raisin, cooked fruit notes

• Factor 3 — Fermentation style and temperature: cooler fermentation preserves delicate fruit aromas; warmer fermentation generates more intense but less complex aromas; yeast strain selection also matters

What are the "formal" wine styles, and how are they defined and classified?

1. Still table wines:

- Red/white

- Dry (0-6g/L of residual sugar) / Off-dry (9-24g/L of residual sugar)

2. Specialty wines

- Sparkling: CO2 from fermentation or added afterwards.

Distinguished by method and sweetness

- Sweet table wines: dessert-style wines.

Distinguished by grape treatment or processing

What are the 4 senses used in wine evaluation, what does each assess, and what is the overall framework?

• Sight — assesses colour (hue) and colour intensity; gives first impression of wine type, age, and health

• Smell — assesses aromas and their intensity

• Taste — assesses acidity (sourness), sweetness, and bitterness — the three main tastes relevant to wine; also saltiness and umami are technically possible

• Touch/Mouthfeel — assesses astringency (drying sensation from tannins) and wine body (weight/viscosity); these are physical sensations, not tastes

• Smell again after swallowing/spitting — assesses aftertaste (finish) and its length; flavour perceived retronasally

• Important distinction: "aroma" = smell perceived by sniffing (orthonasal); "flavour" = smell perceived in the mouth during/after swallowing (retronasal) — both are detected by the olfactory system, not the tongue

How do you evaluate wine by sight, and what are the hue and intensity scales for white and red wines?

Whites

Hue: straw-green → straw → yellow → gold → amber

Intensity: watery → pale → low → medium → high

Reds

Hue: purple → ruby → garnet → orange → brown

Intensity: watery → pale → low → medium → high (opaque)

How does the olfactory system work to detect aromas, and what are the two routes to the olfactory bulb?

Aromas/flavours are volatile and soluble in mucus

They bind to olfactory receptors in the olfactory bulb:

- 5-20 million receptor cells

- Up to 400 different receptor types in humans

- Binding causes signal transmission to the brain

Recent understanding: receptors bind specific chemical features of a molecule, or different molecules can attach to the same binding site in different ways

Many aromas (e.g. "coffee") = multiple compounds interacting with receptors

Signal patterns are processed and stored or matched with existing memory

Two routes to the olfactory bulb:

Orthonasal (aroma) — through the nostrils

Retronasal (flavour) — from the back of the throat

How many aromas can humans distinguish?

Humans may distinguish up to 1 trillion aromas

How do taste buds work, where are they located, and what is the common myth?

Taste buds detect: sweet, sour, bitter, salty, umami

Located in papillae (3 types) on the tongue:

- Circumvallate papillae (back of the tongue)

- Foliate papillae (sides of the tongue)

- Fungiform papillae (tip of the tongue)

Filiform papillae hold NO taste buds (center of the tongue)

Myth: taste buds in certain areas detect specific tastes — THIS IS FALSE

What are the two sensory perception thresholds?

Recognition threshold: lowest concentration of an aroma (in wine) that can be identified; variable in humans, but can be improved with practice

Detection threshold: lowest concentration that can be detected by the human nose

What are the two main approaches to evaluating wine?

Hedonic evaluation: Based on one's own likes

- Used for personal wine buying and food pairing (often used in consumer preference testing)

- Personal bias and highly varied opinions; untrained tasters

Technical evaluation: Uses objective, standardized terminology with training to provide accurate and reproducible sensory data

- Used to evaluate viticultural or oenological approaches, aging potential, pricing

- Used by winemakers, regulators, sommeliers, wine consultants, importers, etc.

What are the complete, ordered steps of a technical wine tasting and what do you assess at each step?

SEE — colour, clarity, sediment, bubbles

SNIFF — smell aromas and their intensity; then rest 30-45 seconds

SWIRL — release volatile aromas and increase their concentration above the wine

SNIFF — confirm aromas and intensity of all aromas/bouquets

SIP — take in a small mouthful (6-10 mL of wine)

SAVOR — roll the wine in the mouth and hold it about 6-8 seconds to warm it, draw air

- Assess acidity, sweetness, bitterness, astringency, body, bubbles, "heat" from alcohol

SPIT (like a pro) — evaluate aftertaste (finish) and length: short <20 sec; medium 20-40 sec; long >40 sec; spitting keeps your senses unbiased

deSCRIBE — describe the components of the wine objectively; keep as a historical record to compare against other wines over time

What are the 6 major pitfalls in wine tasting?

Adaptation: a temporary loss in sensitivity to aroma/taste; occurs as stimulus compound saturates mucus lining of olfactory receptors

Palate fatigue: similar to adaptation, but more a loss of ability to concentrate

Thresholds: people can vary in their thresholds of some tastes/aromas

External noise: outside "noise" (noise, visual distractions, etc.) can alter efficiency of sorting out aromas

Tired/sleepy: harder for your brain to identify aromas efficiently

Anosmia: fully smell "blind" for all aromas; genetic or triggered by polyps/tumour, head injury, or a viral infection

What are "taste modifiers" and how do food, detergents, tasting sequence, and temperature affect wine perception?

Detergents (e.g. toothpaste): modify lipid-containing membranes of receptor cells in taste buds → wine tastes more sour/bitter and less sweet

Food:

- Sweetness in food increases perception of bitterness in wine

- Fat and protein reduce perception of tannin astringency

Sequence of tasting: if a sweet wine is tasted first and a dry wine after, the dry wine tastes sour and bitter

Serving temperature: as temperature increases, sweetness and aromas are perceived more easily, but body and acidity are less apparent