From Grapes to Bottle: How Custom Crush and Contract Sparkling Production Work Together

Most growers who have thought about making sparkling wine have mentally stopped at the same place: somewhere between “I have the fruit for it” and “I have no idea what happens next.” The production process for sparkling wine looks complicated from the outside, the equipment involved is specialized, and the gap between having grapes and having a finished, labeled product ready for market feels wide enough that the idea quietly gets shelved.

It does not have to be that complicated, particularly when you are working with a facility that handles multiple stages of the process under one roof. What follows is a stage-by-stage walkthrough of how a grower or small winery gets from fruit at harvest to finished sparkling wine in the bottle, and where custom crush and contract Charmat production connect into a single production pathway.

Two Ways In

Not every producer starts at the same place, and a full-service contract production relationship can accommodate either entry point.

Grapes to bottle is the full-service path. You bring fruit at harvest. The production partner handles crushing, pressing, juice clarification, primary fermentation, base wine development, Charmat secondary fermentation, cold stabilization, filtration, isobaric bottling, and packaging. You are involved in specification decisions at key stages, but the physical production from raw fruit to finished product happens at the partner facility.

Base wine to bottle is the entry point for producers who already have a still wine program and want to convert some of their production into sparkling. You bring a finished base wine that meets the production partner’s incoming specifications. The process picks up at secondary fermentation and runs through to finished, labeled product.

Both paths arrive at the same place. The choice of entry point affects cost, timeline, and how much control you have over the base wine that goes into secondary fermentation.

Stage 1: Grape Assessment and Harvest Timing

Sparkling base wine is made from grapes harvested earlier and at lower sugar levels than still wine. This is one of the most important decisions in the entire production process, and it is made in the vineyard before a single grape is picked.

The targets look different from still wine:

Parameter	Still Wine Target	Sparkling Base Wine Target
Brix at harvest	22 to 26+	17 to 21
pH	3.3 to 3.6	2.9 to 3.2
Total Acidity	Moderate	High

Harvesting at lower sugar levels preserves the high natural acidity that gives sparkling wine its freshness and structure. It also keeps base wine alcohol at a level, typically 10 to 11.5 percent, that leaves room for the alcohol contribution of secondary fermentation without pushing the finished sparkling wine above target levels.

For Great Lakes producers working with Riesling, Vignoles, Traminette, or other aromatic varieties, the naturally high acidity and moderate sugar accumulation of the region is a genuine advantage for sparkling base wine production. These are varieties that are often harvested before they reach still wine ripeness, which aligns naturally with sparkling base wine targets.

Timing decisions at this stage affect everything that follows. A base wine picked too ripe will be low in acidity and high in alcohol, creating a foundation that secondary fermentation cannot fix. Getting it right at harvest is not recoverable later in the process.

Stage 2: Custom Crush – Destemming, Pressing, and Juice Clarification

Once fruit arrives at the crush facility, the handling decisions made in the first few hours have lasting effects on the quality of the finished sparkling wine.

Destemming and crushing for sparkling base wine emphasizes gentle handling and minimal skin contact. Stem tannins and excessive phenolic extraction from skins and seeds are not desirable in sparkling base wine, particularly for white and rosé styles where freshness and delicacy are the quality targets. A grape crusher destemmer calibrated for gentle handling minimizes the extraction of compounds that would compromise the base wine.

Pressing follows destemming and is arguably the most important equipment decision in the custom crush process for sparkling production. An industrial hydraulic wine press allows controlled, progressive pressure application that extracts clean, low-phenolic juice without the bitterness and astringency that comes from aggressive pressing. The first press fractions, called the free run and early press, are the highest quality juice and are typically kept separate from later press fractions for premium sparkling base wine production.

Juice clarification removes suspended solids from the pressed juice before fermentation begins. Two approaches are commonly used:

Cold settling holds the juice at near-freezing temperatures for 12 to 24 hours, allowing solids to drop naturally to the bottom of the tank before the clear juice is racked off. It is a gentle, low-intervention approach that preserves aromatic compounds well.

Centrifugation achieves the same clarification result significantly faster by spinning the juice at high speed to separate solids mechanically. It is particularly useful when fermentation scheduling or tank availability makes extended cold settling impractical. Fenn Valley’s centrifugation capability is a meaningful operational advantage at this stage, reducing clarification time without sacrificing juice quality.

Clarified juice is the starting point for primary fermentation. The quality decisions made in crushing, pressing, and clarification are embedded in that juice and cannot be corrected later.

Fenn Valley’s Custom Crush Facility handles destemming, pressing, and juice clarification with equipment and protocols designed for the kind of gentle, quality-focused handling that sparkling base wine production requires.

Stage 3: Primary Fermentation and Base Wine Development

Primary fermentation converts the sugars in clarified juice to alcohol, CO2, and a range of flavor and aroma compounds that define the character of the base wine. For sparkling production, the fermentation management goals are somewhat different from still wine production.

The target base wine profile for Charmat sparkling

• Alcohol: 10 to 11.5 percent, leaving room for secondary fermentation contribution
• Residual sugar: Dry to near-dry, as dosage at the end of the process will adjust final sweetness
• Acidity: Preserved and relatively high, as secondary fermentation and dosage will soften perceived acidity somewhat
• Aromatic character: Clean, fruit-forward, variety-expressive, with minimal reductive or oxidative off-notes

Yeast selection matters at this stage. Strains chosen for sparkling base wine production tend to be selected for low volatile acidity production, aromatic preservation, and clean fermentation character rather than the flavor contribution that might be desirable in a full-bodied still wine. The base wine is a foundation, not the finished product.

Yeast nutrition management follows the same principles described in any careful fermentation program: YAN assessment before fermentation, staggered nutrient additions during active fermentation to support yeast health and prevent hydrogen sulfide production, and temperature control throughout. Fenn Valley’s Bulk Wine Production services include fermentation monitoring and yeast nutrition management as core components of the production process, with lab analysis at key points to track fermentation progress and flag any developing issues early.

The question of malolactic fermentation requires a decision at this stage. For aromatic sparkling styles where freshness and fruit acidity are the defining quality attributes, MLF is typically blocked. For fuller, more complex sparkling styles or for base wines with very high natural acidity, partial or complete MLF may be desirable. This decision should be made deliberately before fermentation is complete, as managing MLF after the fact is significantly more difficult than preventing it from the start.

Stage 4: Base Wine Evaluation and Blending

Before secondary fermentation begins, the base wine undergoes a thorough evaluation to confirm it meets the quality and specification targets required for Charmat production.

Lab analysis at this stage typically covers

• Alcohol by volume, to confirm the secondary fermentation contribution will land the finished product at target
• pH and total acidity, to assess structure and stability through secondary fermentation
• Residual sugar, to calculate tirage addition accurately
• Volatile acidity, to confirm the base wine is free of spoilage issues before it enters a sealed fermentation environment
• Free and bound SO2, to assess microbial stability
• Brettanomyces and general microbial screening if indicated

Fenn Valley’s Wine Lab Testing services support this evaluation stage with the full analytical suite required to make a confident go/no-go decision before committing base wine to secondary fermentation.

Blending decisions are also made at this stage for producers working with multiple varieties or vineyard blocks. Blending before secondary fermentation allows the winemaker to target a specific aromatic and structural profile in the finished sparkling wine, and the blending decision is significantly easier to execute before the wine is under pressure in a sealed tank.

Stage 5: Charmat Secondary Fermentation

Secondary fermentation is where the sparkling wine is made. The base wine, now assessed and blended to specification, is transferred to the pressure-rated autoclave tank along with the tirage: a calculated addition of sugar and active yeast that triggers secondary fermentation under sealed, pressurized conditions.

The tirage calculation determines the finished carbonation level of the wine. For a standard sparkling wine at 6 atmospheres of pressure, approximately 24 grams per liter of fermentable sugar is required in the tirage addition. For lower carbonation styles or for producers targeting a specific CO2 volume, the calculation adjusts accordingly.

Once the tank is sealed, secondary fermentation proceeds over a period of weeks under controlled temperature. Pressure builds gradually as CO2 is produced and retained in the sealed vessel. Temperature monitoring through this period influences both the rate of fermentation and the character of the finished wine, with cooler temperatures generally producing finer bubble structure and more delicate flavor development.

What is happening in the tank during this period goes beyond carbonation. The yeast are producing additional flavor compounds, consuming residual oxygen, and contributing to the overall complexity of the wine in ways that force carbonation cannot replicate. The sealed, pressurized environment is doing work that shows up in the glass.

Stage 6: Cold Stabilization, Filtration, and Quality Control

After secondary fermentation is complete, the wine requires stabilization and clarification before it can be bottled.

Cold stabilization under pressure chills the wine to near-freezing temperatures while maintaining the CO2 in solution. This causes tartrate crystals to precipitate out of solution in the tank rather than forming in the bottle after packaging, which is a presentation problem that consumers find alarming even when it is harmless. Cold stabilization in the Charmat tank is more straightforward to manage than cold stabilization of still wine, because the process happens in a controlled sealed environment before the wine ever encounters a bottle.

Filtration before isobaric transfer removes residual yeast cells and any remaining solids, producing a brilliantly clear wine ready for packaging. The filtration step is critical for microbiological stability in the finished product. A wine that enters the bottle with live yeast present will continue fermenting, creating exactly the overcarbonation and instability problems that careful Charmat production is designed to avoid.

Lab analysis at this stage confirms the wine is ready to bottle: carbonation level, residual sugar, SO2, microbial stability, and filtration suitability are all verified before packaging begins.

Stage 7: Isobaric Bottling, Dosage, and Closure

Dosage is the final winemaking decision before the bottle is sealed. A small addition of wine and sugar solution, called the liqueur d’expedition, adjusts the final residual sugar level of the finished sparkling wine to hit the target style.

Style	Residual Sugar
Brut Nature	Less than 3 g/L, no added sugar
Extra Brut	0 to 6 g/L
Brut	Less than 12 g/L
Extra Dry	12 to 17 g/L
Dry (Sec)	17 to 32 g/L
Demi-Sec	32 to 50 g/L

Isobaric bottling transfers the dosed wine from the tank to bottles under counter-pressure, maintaining the CO2 in solution throughout the transfer and fill. This is where the specialized filling equipment earns its importance. A standard still wine filler cannot do this. The isobaric filler maintains equal pressure between the tank, the transfer line, and the bottle being filled, so no CO2 escapes and no oxygen enters during the fill.

Closure selection follows bottling. Crown caps, traditional corks with wire cages, and screw caps are all available options depending on the style and market positioning of the finished product.

Stage 8: Labeling, TTB Compliance, and Packaging

Before sparkling wine can be sold commercially, federal label approval is required. The TTB Certificate of Label Approval, or COLA, must be obtained for each label used on wine sold in interstate commerce. The application requires specific mandatory information: the brand name, the class and type designation, net contents, alcohol content, the government health warning statement, and the bottler or producer information.

Sparkling wine labeling has additional requirements, including the carbonation method and style designation. TTB approval timelines vary but typically run several weeks for straightforward applications. Preparing the application correctly the first time avoids the delays that come from back-and-forth with the agency over missing or incorrect information.

Fenn Valley’s Custom Packaging Solutions include TTB compliance support and label assistance alongside bottling and packaging services, so the regulatory piece of getting product to market does not fall entirely on the producer.

Production Calendar Planning

The full timeline from harvest to finished sparkling wine depends on the entry point and the production schedule, but a general framework for planning purposes:

Stage	Approximate Timeline
Harvest and custom crush	1 to 3 days at crush
Primary fermentation	3 to 5 weeks
Base wine evaluation and blending	1 to 2 weeks
Charmat secondary fermentation	3 to 6 weeks
Cold stabilization and filtration	1 to 2 weeks
Isobaric bottling and dosage	1 to 2 days
TTB COLA approval	4 to 8 weeks (can run concurrently with production)
Total grape to bottle	Approximately 4 to 6 months

COLA application is worth initiating early in the production process. The approval timeline is largely outside your control, and submitting while production is underway rather than waiting until the wine is ready to bottle avoids a situation where finished product is sitting in tank waiting for a label.

For producers working with a base wine to bottle entry point, the timeline compresses by approximately the primary fermentation period.

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