Sauvignon Blanc — New Zealand Style Winemaking Protocol

The aromatic ceiling is set in the vineyard: the pool of thiol precursors and methoxypyrazine arrives with the fruit, and the cellar can only realise or waste it. Vine nitrogen status correlates with both thiol precursors and juice YAN, so post-veraison foliar nitrogen (urea) — paired with foliar elemental sulfur, the atom at the heart of the thiol — is one of the few levers that genuinely raises aromatic potential rather than just preserving it.

Avoid water stress. It shrinks the canopy, over-exposes the fruit and accelerates the loss of the green methoxypyrazine that frames the style, while limiting precursor and nitrogen accumulation. Aim for moderate vigour, a healthy but uncompacted canopy, and moderate fruit-zone shading to retain pyrazine without inviting Botrytis.

The style is built on picking relatively early — around 19–22 °Brix with titratable acidity still 7–9 g/L and pH at or below 3.25. As ripening advances, methoxypyrazine falls while the tropical thiol character rises and acidity drops, so the classic approach spreads harvest across dates or blocks and blends: an earlier fraction for pyrazine, nerve and acidity, with a later fraction for passionfruit and tropical volume.

Harvest cold, at night or dawn. Machine harvesting is typical and even useful, because skin contact in transit extracts thiol precursors and pyrazine — provided the fruit is protected (below) and free of Botrytis, whose laccase oxidises the very thiols you are chasing.

From reception on, the operating principle is reductive: oxygen is the enemy of thiols. Add SO₂ (30–50 mg/L) at reception and, with machine fruit, consider ascorbic acid as an immediate antioxidant partner; blanket vessels and lines with inert gas.

Pre-fermentation skin contact is a two-edged tool — it extracts precursors and pyrazine but also phenolics and oxidation risk. For the crisp style keep it short and cold (a few hours at 8–12 °C under SO₂), or skip it entirely in favour of whole-bunch pressing for the most delicate expression.

Press cold fruit gently: a pneumatic press, low pressure, inert atmosphere, soft cycles. Keep press fractions separate — free run and the light pressings carry the fine, aromatic core of the style, while hard pressings bring more phenolics and coarser character and are best vinified apart.

Hyperoxidation — deliberately stripping oxidisable phenolics to make an oxidation-stable wine — is antithetical here: it would destroy the thiols the style depends on. Handle reductively, not oxidatively.

Juice clarity is a defining lever, and the goal is not the cleanest possible juice. Cold-settle at 8–12 °C for 12–48 hours, or use flotation. Target 100–200 NTU for a crisp, pungent, cutting style, or 200–350 NTU for more texture, lees complexity and thiol expression — the solids carry precursors and nutrients but raise the risk of reduction.

Juice that is too clean (below ~80–100 NTU) ferments sluggishly and more reductively; juice that is too turbid (above ~350 NTU) turns reductive and vegetal. Keep solids to roughly 1–2% by volume; a good default is ~150–200 NTU, raised deliberately when chasing texture.

Use a pectolytic clarification enzyme to speed cold settling or enable flotation and to hit the turbidity target with control. Choose a purified pectinase low in cinnamyl-esterase side-activity: cinnamyl esterase releases hydroxycinnamic acids that POF⁺/Brett yeast can turn into volatile phenols (medicinal, plaster-like notes) that ruin the style.

Aromatic glycosidase enzymes, used to free terpenes, are not relevant — Sauvignon Blanc is thiol-driven, not terpene-driven — so they are unnecessary here.

Yeast is the single biggest aromatic lever in the cellar. Thiol release depends on a strain's β-lyase activity, which cleaves the cysteinylated precursors, and the passionfruit note depends on its ability to acetylate 3MH into 3MHA. Choose a Saccharomyces cerevisiae strain selected for thiol expression — high β-lyase, good acetate-ester production and preferably low nitrogen demand so it does not push higher alcohols.

Sequential or co-inoculation with a non-Saccharomyces yeast such as Torulaspora delbrueckii or Metschnikowia pulcherrima can add thiols and texture; manage nutrition and the start carefully to avoid reduction. Avoid spontaneous fermentation for this style — it risks reduction, volatile acidity and volatile phenols, and cedes control of the thiol expression.

Nutrition has a double job: feed the yeast so cold, clean, reductive ferments do not throw hydrogen sulfide, and support thiol release and ester formation without overloading ammonia. Measure juice YAN and correct toward ~200–250 mg N/L, adjusted down for low-demand strains; excess DAP pushes higher alcohols and can blur varietal definition.

Favour complex, organic nutrition (inactivated-yeast derivatives supplying sterols and unsaturated fatty acids) for membrane health and less H₂S, with DAP as a complement rather than the base, and consider glutathione-rich yeast derivatives in the juice — glutathione is an antioxidant that protects 3MH. Add a sterol-bearing rehydration nutrient at inoculation and complex nutrient plus DAP around one-third of the way through fermentation; avoid late DAP.

Ferment cool — 12–16 °C, typically around 14–15 °C. Cold preserves the volatile esters and acetates (including 3MHA) and the fresh, fruity signature of the young style.

But too cold (below ~12 °C) stresses the yeast into H₂S and stuck ferments, so do not drop below what the strain tolerates. A fraction run slightly warmer can add volume and texture for blending, at the cost of some pungency.

The rule differs before and after fermentation. During fermentation the juice is blanketed by CO₂ and the yeast scavenges oxygen fast, so a micro-addition of O₂ in the active phase (or adequate lipids and nutrition) supports yeast health and reduces H₂S with little thiol loss.

After fermentation the regime is strictly reductive: every milligram of oxygen now destroys thiol directly — inert cover, closed and minimal transfers, SO₂ maintained, dissolved oxygen measured, and a short time on fine lees as a reductive buffer. Treat oxygen pickup as a budget summed across the wine's life and keep the total low; skip micro-oxygenation, which is a red-wine tool. Go easy on copper fining — it strips desirable thiols as well as sulfides, so prevent reduction rather than correct it.

Sauvignon Blanc is protein-unstable and needs bentonite to pass a heat test, and both the timing and the type matter because they touch the fragile aroma. Because thiols are released during fermentation, bentonite added early — to the juice or during fermentation — removes protein before the thiols exist and spares aroma, whereas bentonite on finished wine strips thiols along with protein. Favour early addition and a minimal, heat-test-guided polishing dose at the end.

On type, sodium (or sodium-activated) bentonite has higher adsorption so it needs a lower dose — less aroma stripping — at the cost of more lees volume and some added sodium; calcium bentonite compacts better with less wine loss but needs more, and releases calcium that compromises tartrate stability. For this style, sodium or sodium-activated bentonite at the minimum effective dose is the base choice.

A cold-served, crystal-clear white must be stable to potassium bitartrate and, where calcium is present, calcium tartrate. Test with a conductivity mini-contact test rather than relying on a freeze test. Cold contact (chilling near freezing with seeding) is robust but energy-hungry and an extra oxygen-pickup window, so inert it if used; electrodialysis and ion exchange are gentler on aroma; and additive inhibitors avoid the cold step entirely.

Carboxymethylcellulose (CMC) is well suited here — effective against bitartrate and gentle on aroma — but must be added only after protein (bentonite) fining and filtration, or it hazes with protein. Because calcium tartrate does not reliably drop out with cold, avoid calcium sources — calcium bentonite, chalk deacidification, concrete tanks — which is a further reason to prefer sodium bentonite.

Work in molecular SO₂, the active fraction, which depends on free SO₂ and pH (molecular = free / (1 + 10^(pH − 1.81))). The style's low pH (3.0–3.25) means a given free level yields more molecular, so a protective target of about 0.8 mg/L molecular lands near 30–38 mg/L free — recompute against the real pH. The style does not go through malolactic fermentation, so set SO₂ right after alcoholic fermentation to protect thiols from the first hour, and re-check and top up before and after each racking and immediately before bottling.

Rack closed and inert — bottom-fill, no splashing, lines and receiving vessel purged with inert gas, dissolved oxygen measured, with a sacrificial SO₂ before any oxidative operation. Bottling is the highest-risk oxygen event: minimise total package oxygen by inerting the bottle and jetting the headspace, top free SO₂ to target, and consider ascorbic acid with SO₂ (never ascorbic alone, which needs SO₂ to mop up its peroxide). Bottle under a screwcap with a low-OTR liner to hold the reductive, fresh style in bottle.

The New Zealand archetype is unoaked — stainless steel, reductive, from start to finish — because oak would bury the thiols and freshness that define it.

A barrel-fermented Sauvignon Blanc does exist (the Bordeaux Blanc / Pessac-Léognan / Fumé register, fermented in mostly older or large-format oak for texture rather than vanilla), but that is a different style deserving its own protocol.