Enzymatic Treatment of Grape Skins

Enzymatic treatment applies food-grade pectinolytic enzyme preparations to freshly crushed grape must to biochemically break down the polysaccharide structures of the grape skin cell wall. These preparations are complex cocktails primarily based on pectinases, but also containing complementary hemicellulase and cellulase side activities that together attack the pectin, hemicellulose, and cellulose fractions of the cell wall. The primary microbial source for commercial preparations is Aspergillus niger, a fungus long recognized as safe for food enzyme production. By partially hydrolyzing the cell wall architecture, the enzymes increase the permeability of grape skin cells, allowing anthocyanins, tannins, aroma precursors, and flavor compounds to diffuse freely into the juice phase without requiring extended maceration time or elevated temperatures.

• Pectinases target the pectin fraction of the cell wall; hemicellulases and cellulases provide complementary side activity on hemicellulose and cellulose components
• Commercial enzyme preparations are derived principally from Aspergillus niger via industrial submerged fermentation, with GRAS (generally recognized as safe) status for food applications
• The cuticle and wax layer on grape skins limit enzyme penetration from outside the berry, so enzymes work most effectively from the pulp side after crushing

Enzymes are dissolved in water and added to crushed must as early as possible, ideally at the crusher. They adsorb onto accessible cell wall surfaces and begin catalyzing hydrolysis of polysaccharide bonds, progressively increasing cell permeability and releasing entrapped compounds into the liquid phase. Fast-acting preparations such as Rapidase Expression Aroma can complete their core extraction activity within 2 to 3 hours; others act more progressively over several hours to a full overnight period. Standard protocols recommend allowing enzymes to act before yeast inoculation, since rising alcohol levels during fermentation inhibit enzymatic activity. Enzyme activity is also strongly temperature-dependent, with most commercial preparations performing best between 20 and 30 degrees Celsius and losing effectiveness below 10 degrees Celsius.

• Add at crushing, dissolved in water at a ratio of approximately 1 to 10 by weight, and distribute evenly through the must
• Allow enzymes to act for at least several hours, ideally overnight, before inoculating with yeast; avoid adding bentonite for at least 24 hours as it will inactivate enzymes
• Best activity between 20 and 30 degrees Celsius; activity slows significantly below 10 degrees Celsius and is inhibited by high alcohol levels after fermentation begins

In red winemaking, macerating enzyme preparations accelerate and enhance the extraction of anthocyanins and tannins from grape skins, producing wines with deeper, more vivid color, increased total polyphenol content, and improved color stability compared to unaided maceration over the same period. Research has demonstrated measurable increases in anthocyanin and polyphenol content with commercial enzyme use versus control wines. The Lallzyme EX preparation is designed to produce a gentler maceration suitable for early-drinking red wines with soft tannins and vibrant fruit; Lallzyme EX-V is formulated to extract color and tannins with greater structural integration for wines intended for aging. In white winemaking, aromatic enzyme preparations act on skin-contact juice to release glycosylated aroma precursors, including monoterpenes and norisoprenoids, enhancing varietal character without the oxidative risk of prolonged skin contact.

• Color and polyphenol content: research on Cabernet Sauvignon found enzyme treatments increased polyphenols by approximately 15% and anthocyanins by approximately 10% versus controls
• Tannin character: Lallzyme EX targets softer, rounder tannin profiles for early-release reds; Lallzyme EX-V aims for greater structure and color stability in age-worthy styles
• Aromatic enhancement in whites: enzymatic preparations with glycosidase side activity can release bound monoterpenes (nerol, geraniol, linalool) and norisoprenoids from their glycosylated precursors in the skins

Enzymatic treatment is most broadly applied in white and rosé winemaking, where pectinases are routinely used during pressing and settling to break down pectin, reduce viscosity, improve clarification, and increase juice yield. In red winemaking, macerating enzyme preparations are added post-crushing to accelerate phenolic extraction, particularly when maceration time is constrained by winery capacity or when working with varieties or vintages where natural extraction is slow. Aromatic enzyme preparations are particularly effective with grape varieties that carry high concentrations of glycosylated aroma precursors in their skins, including Gewurztraminer, Riesling, Viognier, Chenin Blanc, and Albariño. Enzymes are generally not needed or recommended after alcoholic fermentation is complete, as alcohol inhibits their activity.

• White and rosé winemaking: pectinases added at pressing or to juice improve settling speed, clarification, filterability, and juice yield across virtually all varieties
• Red winemaking: macerating enzyme blends (pectinase, hemicellulase, cellulase) added at crushing to increase color and tannin extraction within a defined maceration window
• Aromatic white varieties (Gewurztraminer, Riesling, Viognier, Albariño): enzyme preparations with glycosidase side activity maximize release of bound monoterpene aroma precursors from skins
• Botrytis-affected fruit: beta-glucanase preparations are used to break down Botrytis-derived glucans that otherwise cause severe filtration problems

The two dominant enzyme companies in winemaking are dsm-firmenich (whose Rapidase portfolio is distributed by Oenobrands) and Lallemand (whose Lallzyme range covers multiple red and white applications). Rapidase has been produced since 1922 and has evolved into a broad portfolio including Rapidase Expression Aroma for skin-contact aromatic whites, Rapidase Fast Color for short-maceration reds, and Rapidase Clear Extreme for white and rosé juice clarification. Lallemand offers Lallzyme EX for early-drinking, fruit-forward reds, Lallzyme EX-V for structured age-worthy reds requiring stable color and tannin integration, and Lallzyme C-MAX for white and rosé clarification under difficult settling conditions. Scott Laboratories also supplies the Scottzyme range, including Scottzyme Color X for anthocyanin and tannin release in reds.

• Rapidase Expression Aroma (Oenobrands/dsm-firmenich): low-dose aromatic maceration enzyme for skin-contact white wines; active from 8 degrees Celsius; typically completes extraction in 2 to 3 hours
• Lallzyme EX (Lallemand): pectinase, galactanase, and cellulase blend for early-release red wines; dosed at 20 to 30 grams per ton; best activity at 20 to 30 degrees Celsius
• Lallzyme EX-V (Lallemand): precision blend for structured reds targeting anthocyanin-tannin binding and long-term color stability; dosed at 30 to 40 grams per ton
• Scottzyme Color X (Scott Laboratories): pectinase with cellulase side activity specifically for anthocyanin and tannin release in red wine maceration

Effective enzymatic treatment requires correct product selection for the application, appropriate dosage according to manufacturer guidelines, and attention to a few key inhibitors. Enzymes are proteins and are inactivated by bentonite and charcoal; winemakers should wait at least 24 hours after enzyme addition before adding bentonite. Most commercial preparations are active across a pH range of approximately 2.5 to 5.5, which encompasses the typical must pH range, and are tolerant of normal sulfite levels. Temperature is the primary practical variable: activity slows markedly below 10 degrees Celsius and enzyme use is generally not recommended after alcoholic fermentation is underway due to alcohol inhibition. An important consideration in red winemaking is beta-glucosidase side activity in some preparations, which can degrade anthocyanins and reduce color; producers should select preparations verified to have low or negligible anthocyanase activity when color preservation is the goal.

• Inactivation risks: bentonite and charcoal inactivate enzymes; wait at least 24 hours after enzyme addition before any bentonite addition
• Sulfite timing: allow at least 15 to 20 minutes after sulfiting crushed fruit before adding enzymes, as sulfite can temporarily inhibit activity
• Beta-glucosidase awareness: some enzyme preparations contain beta-glucosidase activity that can degrade anthocyanins in red wine; select preparations with confirmed low anthocyanase side activity for color-critical red applications
• Bench trials are strongly recommended when introducing a new enzyme preparation or working with an unfamiliar grape variety or vintage condition