Glossary

Plain-English definitions of 45 common meadmaking and fermentation terms.

A B C D F G H K L M O P R S T Y

A

ABV: Alcohol by volume. The percentage of ethanol in the finished mead, expressed as a fraction of total liquid volume. Calculated from the difference between original gravity and final gravity.
Aerating: Introducing oxygen into the must during early fermentation to support yeast growth and cell membrane health. Aeration is beneficial in the first 24–48 hours but harmful after the 1/3 sugar break when it can promote oxidation.
Attenuation: The degree to which yeast has fermented the available sugars in the must, expressed as a percentage of the original gravity points consumed. Higher attenuation = drier mead.

B

Bentonite: A calcium montmorillonite clay used as a fining agent to clarify mead. It carries a negative charge that attracts positively charged protein particles (common in heather honey meads), causing them to clump and settle. Added at pitch or shortly after.
Bochet: A style of mead made with caramelised (burned) honey. The caramelisation process changes the flavour profile significantly — adding notes of toffee, marshmallow, and dark fruit — and partially breaks down fermentable sugars, lowering predicted OG.
Braggot: A hybrid beverage made with both honey and malt (and optionally hops). It bridges the gap between mead and beer in character, and typically uses a beer or ale yeast strain.
Brix: A unit of sugar concentration equal to grams of sucrose per 100 grams of solution. In mead, Brix is used interchangeably with approximate sugar percentage and is calculated from specific gravity. The calculator uses Brix = (OG − 1.000) × 220.

C

Campden: Potassium or sodium metabisulphite, used to sterilise equipment and inhibit wild yeast and bacteria before pitching a cultured strain. Also used post-fermentation as an antioxidant. One Campden tablet per 4.5L is the standard dose.
Cyser: A melomel made with apples or apple juice. Cysers bridge mead and cider and are often produced with cider-focused yeast strains (e.g. WLP775) that preserve apple character while fermenting dry.

D

DAP: Diammonium phosphate. An inorganic nitrogen source with a YAN density of 210 ppm/g/L. Highly concentrated and effective in early fermentation, but should not be used after the must has exceeded approximately 9% ABV, as yeast cannot assimilate inorganic ammonium at higher alcohol levels.
Degassing: Removing dissolved CO₂ from the must by stirring or agitation. Essential before each nutrient addition to prevent violent foam-over. Also done periodically during fermentation to reduce off-gas stress on yeast.

F

F:G ratio: Fructose-to-glucose ratio. Honey sugar composition varies by variety — acacia has a very high F:G (~1.60) while rapeseed has a low F:G (~0.93). Standard yeast strains preferentially ferment glucose; musts with very high F:G ratios are prone to stalling without a fructophilic yeast strain.
Fermaid K: A blended nutrient containing DAP, inactivated yeast, yeast hulls, and micronutrients. YAN density: 100 ppm/g/L. More concentrated than Fermaid O; subject to the 9% ABV inorganic nitrogen cutoff.
Fermaid O: An organic nitrogen source derived from inactivated yeast cell walls. YAN density: 40 ppm/g/L. The recommended primary nutrient in TOSCA 2.0 — it provides FAN, vitamins, and cell wall components and can be used through all stages of fermentation.
Fermentation: The metabolic process by which yeast converts fermentable sugars into ethanol, carbon dioxide, and flavour compounds. In mead, primary fermentation typically runs 2–6 weeks depending on OG, temperature, yeast strain, and nutrient levels.
FG (Final Gravity): The specific gravity of the mead once fermentation has reached completion or been stopped. Used together with original gravity to calculate ABV. A fully dry mead typically finishes around 0.990–1.000.
Finings: Clarifying agents added to mead post-fermentation to accelerate clearing. Common options include bentonite (protein fining), Isinglass (collagen-based), kieselsol, and chitosan. Most home meadmakers achieve clarity with time and cold-crashing alone.
Fructophilic: Describes a yeast strain with enhanced fructose transport capacity (typically the HXT3 gene). Fructophilic strains can metabolise fructose at the same rate as glucose, eliminating the stall risk associated with high-F:G honey varieties like acacia and tupelo.

G

GoFerm PE: GoFerm Protect Evolution. A yeast rehydration nutrient that protects cell membranes during the osmotic shock of rehydrating dry yeast. Added to the warm rehydration water before the yeast, never directly to the must. YAN density: 30 ppm/g/L (for calculator purposes). Typical dose: 1.25× dry yeast weight.
Gravity: Shorthand for specific gravity — the density of the must or mead relative to water. Gravity indicates sugar concentration before fermentation and alcohol content after. See Original Gravity, Final Gravity, and Specific Gravity.

H

Honey must: The mixture of honey and water (and any fruit or adjuncts) before or during fermentation. "Must" is the technical term for pre-fermented fruit or honey liquid, borrowed from winemaking.
Hydromel: A low-gravity mead made with a smaller honey-to-water ratio, typically targeting OG 1.030–1.060 and finishing at 4–8% ABV. Named from the French for "water-honey." The sessionable end of the mead style spectrum.

K

Kveik: A group of traditional Norwegian farmhouse yeast strains with unusually high temperature tolerance (up to 40°C for some strains). Voss Kveik is the most commercially available and produces characteristic orange and citrus ester notes at high fermentation temperatures. Valued in meadmaking for extremely fast fermentation timelines.

L

Lees: The sediment that accumulates at the bottom of the fermenter during and after fermentation, consisting of dead yeast cells, honey solids, and precipitated proteins. Racking off lees at the appropriate time prevents autolysis (yeasty, meaty off-flavours) in the finished mead.

M

Mazer: An archaic term for a meadmaker, derived from the Middle English word for a large drinking cup. Still used in the modern meadmaking community (particularly in competition and hobbyist contexts).
Mead: An alcoholic beverage produced by fermenting honey dissolved in water. The oldest known alcoholic drink. Mead ranges from bone-dry to dessert-sweet, and from still to sparkling, encompassing traditional, fruit (melomel), spiced (metheglin), apple (cyser), caramelised (bochet), and malt (braggot) sub-styles.
Melomel: A mead made with the addition of fruit. The fruit contributes fermentable sugar, flavour, colour, and often acidity. Almost any fruit can be used; common examples include raspberry, blackberry, cherry, and blueberry.
Metheglin: A mead made with the addition of spices, herbs, or other botanical adjuncts. Examples range from simple cinnamon-vanilla combinations to complex multi-herb blends inspired by historical recipes.
Must: The unfermented or actively fermenting liquid in a batch of mead or wine. In mead, the must is typically honey dissolved in water, potentially with fruit and adjuncts added.

O

OG (Original Gravity): The specific gravity of the must before fermentation begins, measured after all ingredients (honey, fruit, adjuncts) have been combined. OG indicates the total fermentable sugar content and is used to calculate predicted ABV. A typical traditional mead has OG 1.090–1.120.

P

Pectolase: Pectic enzyme (also sold as Pectinase). Used to break down pectin in fruit additions, preventing pectin haze in the finished mead and improving juice extraction. Added 24 hours before pitching yeast or at the time of fruit addition to secondary. Essential for high-pectin fruits (apple, blackcurrant, gooseberry, sloe).
pH: A measure of acidity on a logarithmic scale from 0–14. Target must pH for mead is 3.7–4.0. Below 3.2, yeast enzyme activity drops sharply and fermentation stalls. Monitored with a calibrated pH meter; corrected with potassium bicarbonate.
PPM: Parts per million. The standard unit for expressing small concentrations in meadmaking — YAN requirement, nutrient doses, sulphite additions. Equivalent to milligrams per litre (mg/L) in water-based solutions.
Punch-down: Manually pushing a fruit cap (floating solids) back into the liquid to ensure good extraction and prevent acetobacter growth on the exposed surface. Required for primary ferments with whole fruit additions.

R

Racking: Siphoning or pumping mead from one vessel to another, leaving lees behind. The primary reasons to rack are: moving from primary to secondary fermentation, removing from a fruit cap, and clarifying before packaging. Over-racking introduces oxygen and should be avoided in late fermentation.

S

SNA (Staggered Nutrient Addition): A general term for any protocol that divides the total nutrient requirement across multiple additions during early fermentation, rather than adding all nutrients at once. TOSCA 2.0, TOSNA, and TiOSNA are all SNA protocols.
Sparkling mead: Mead with dissolved CO₂ producing carbonation, either naturally (bottle conditioning with residual or added sugar) or forced (kegging with CO₂). Requires tolerance for approximately 2–3 volumes of CO₂ and appropriate packaging pressure.
Specific Gravity: The ratio of the density of a liquid to the density of pure water at the same temperature. Pure water = 1.000. Honey must at OG 1.110 is 11% denser than water. Measured with a hydrometer (sample drawn) or refractometer (a few drops).
Stall (fermentation): When active fermentation stops before reaching the target final gravity, leaving residual fermentable sugar. Common causes: nutrient deficiency, pH too low, temperature too cold, yeast ABV tolerance exceeded, or fructose accumulation in non-fructophilic yeast with high-F:G honey.

T

TiOSNA: Time and Organic Staggered Nutrient Addition. A hybrid nutrient protocol combining time-based early additions with a final addition timed to the 1/3 sugar break measured by hydrometer. More complex than TOSCA 2.0.
TOSCA 2.0: Time-based Organic Staggered Compound Addition. The current best-practice nutrient protocol, using four time-based additions (24h, 48h, 72h, 96h after pitch) plus GoFerm PE at rehydration. No gravity measurements required. See the TOSCA 2.0 guide for full details.
TOSNA: Time-Organic Staggered Nutrient Addition. An older gravity-based SNA protocol where additions are triggered by Brix or specific gravity milestones rather than hours. Effective but requires a hydrometer for accurate timing.
Traditional mead: A mead made from honey, water, and yeast only — no fruit, spices, or other adjuncts. The character comes entirely from the honey variety and fermentation management. Sometimes called "show mead" in competition contexts.

Y

YAN: Yeast Assimilable Nitrogen. The fraction of total nitrogen in the must that yeast can metabolise for growth and fermentation. Measured in ppm (mg/L). The required YAN is calculated from sugar concentration and yeast nitrogen demand. Insufficient YAN causes H2S, stalls, and off-flavours.
Yeast nutrient: A general term for products that supply yeast with the nitrogen, vitamins, and micronutrients absent from honey. Specific products include GoFerm PE (rehydration), Fermaid O (organic nitrogen), Fermaid K (blended), and DAP (inorganic nitrogen). Generic yeast nutrient blends from homebrew retailers vary widely in composition.