Glossary of Winemaking Terms

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Labrusca: Species of grape (Vitis) native to North America characterized by a strong foxy (methyl anthranilate) note

Laccase: Phenol oxidase produced by B. cinerea and other molds; resistant to sulfur dioxide (SO 2); can be inactivated by HTST treatments

Lactic Acid/Lactate: Organic acid universally present in prokaryotes and eukaryotes; both intermediate and an end product of metabolism; CH 3CHOHCOOH

Lactic Acid Bacteria: General term for bacteria producing lactic acid as an end product of fermentation

Lactobacillus: Genus of lactic acid bacteria; contains both hetero and homofermentative organisms; some are important spoilage organisms of wine

Lactone: Components of wine aroma formed from the internal esterification of molecules containing a hydroxyl and carboxylic acid group; also extracted from barrel wood or produced by yeast


Lane-Eynon: Method for the measurement of reducing sugar based on titration with alkaline copper sulfate

Lateral Shoot: A shoot that grows out from a leaf axis on the main shoot; a secondary shoot.

Lead: A heavy metal with atomic number 82; Lead is an environmental contaminant and has been phased out as capsule material; lead contamination can also be found in some wines but most is precipitated on the yeast lees.

Leaf: The chlorophyll-enriched photosynthetic component of a plant; grape leaves vary by variety and can be used in vine identification.

Leaf Drop: The loss of leaves from the vines that occurs as vines enter dormancy.

Leaf Hopper: Insects ubiquitous in vineyards capable of causing vine damage; Erythroneura elegantula, common leaf hopper and Erythroneura variabilis, the variegated leaf hopper both can cause damage by feeding on leaves.

Leaf Removal: In viticulture, refers to the practice of deliberate removal of some leaves from the vine; generally around clusters to improve air circulation and reduce incidence of bunch rot; can also be used to impact fruit composition

Leaf To Fruit Ratio: In viticulture, refers to the total leaf surface area on the vine as related to cluster weight; leaves are the sites of photosynthesis and the creation of sugar that is translocated to grapes during grape maturation; vine balance requires an appropriate level of leaf area per cluster to attain desired sugar levels in the fruit.

Leaf Water Potential: A measure of the water status of leaves; can be used to guide irrigation practices and assess vine water status.

Leafroll Virus: Ubiquitous virus found in grape vines; a complex of different viruses that can reduce vine yields and negatively impact ripening

Lees: General term for the residue settling to the bottom of a tank; can be derived from the grapes (grape lees) or following microbial activity (yeast lees)

Lees Contact: In winemaking, refers to the practice of leaving wine in contact with the settled yeast lees during aging; see sur lie aging

Lees Stirring: In winemaking, refers to mixing the lees and wine during lees contact and aging; see batonnage.

Legs: In wine tasting, refers to the adherence of wine as a viscous liquid to the glass following swirling

Leucine: A non-polar amino acid;
3 letter code: Leu; 1 letter code: L; mw: 131.18; pKa: 2.36; 9.60; pI: 5.98

Leucoanthocyanin: Colorless anthocyanin; containing hydroxyl groups at the 3 and 4 position of the C or bridge ring of the flavanoid

Leuconostoc : Genus of lactic acid bacteria; the principle agent of the malolactic fermentation in wine was formerly known as Leuconostoc oenus, now called Oenococcus oeni

Levorotary: An optically active substance is one that rotates the plane of polarized light; if that rotation is to the left or counterclockwise the substance is levorotary

Lie(s): French word for lee(s).

Light Struck: Term describing wine that has been exposed to light which catalyzes certain reactions in the wine; light struck wines are described as plastic, wet dog and corn nuts; a particular problem for sparkling wines as the carbon dioxide enhances perception of flavorants in the wine

Lignin: Polymer of phenolic residues found in cell walls of plants conferring strength and rigidity; particularly in woody plants

Limestone: In soil, rock composed of calcium carbonate

Limonene: Widely distributed terpene hydrocarbon that occurs in essential oils (as of oranges or lemons) and has a lemon odor; can be found in wines

Linalool: Terpene alcohol (terpenol); fragrant liquid alcohol that occurs both free and in the form of esters in many essential oils and is used in perfumes, soaps, and flavoring materials; described as citrus floral

Linear Regression Analysis: Determination of the relationship between two variables, such as amount of protein and absorbance; straight lines follow the formula y = mx + b where y is the dependent variable, x the independent variable, m the slope of the line and b the y intercept; the slope and intercept can be calculated from the experimental data of known concentrations, then knowing the absorbance of an unknown allows calculation of the protein concentration; a correlation coefficient for the line can be calculated which describes the goodness of fit of the relationship between the two variables

Linkage Mapping: Term used in genetic analysis (breeding) to define and estimate the physical relationship between specific genes or traits on a chromosome.

Lipid: Generally, a term for compounds that are insoluble in water and extracted from cells by organic solvents; specifically refers to fats which are comprised of carboxylic acid; fats derived from glycerol are called triglycerides; predominant in membrane bilayers; function as an energy reserve in animals

Lipoprotein: Protein covalently attached to a lipid moiety

Loam: In soil, the mixture of clay, sand and silt

Lyre: In viticulture, a canopy training system that splits the canopy horizontally into two curtains

Lysine: A basic amino acid;
3 letter code: Lys; 1 letter code: K; mw: 182.70 (LysHCl); pKa: 2.18; 8.95 ( a amino); 10.53 ( e amino); pI: 9.74

Lysozyme: Small enzyme found in animal secretions (i.e., tears, saliva) that cleaves the peptidoglycan layer found in gram positive bacteria leading to lysis of the target cells; effective against the gram positive lactic acid bacteria in wine