The press is the crucial link between the vineyard and the cellar. It determines how much of the grapes’ quality potential actually makes it into the must. Anyone who wants to work in the premium segment with as few corrective interventions and additives as possible—and anyone who wants to produce wine as cost-effectively as possible—must therefore plan precisely even before the first pressing step.
Pressing is not an isolated mechanical process. The condition of the grapes, the timing of the harvest, the outside temperature, the weather, the transport containers, the waiting time, and the distance to the press all combine to determine the quality that can actually be achieved. A good press cannot restore damaged, overheated, or microbiologically contaminated grapes to their original, undamaged state.
The most important practical implication is therefore this: the vineyard, harvest logistics, grape reception, and pressing must be planned as a single, integrated process. It is not the maximum rated capacity of a single machine that matters, but rather a consistent flow of material without long downtimes or unnecessary transfers. Those who wish to work with reduced SO₂ levels must rely on particularly gentle processing and consistent control of oxygen exposure. Good process management can reduce the need for protective and corrective measures, but it is no substitute for targeted oenological safeguards.
The number of harvest assistants or full-time harvesters, the transport capacity, and the realistic duration of a pressing cycle must all be in balance. If more grapes arrive than can be processed, delays will occur. If the press is too large for the actual daily throughput, it often takes too long to fill it completely. Both situations increase the risk of oxidation, unwanted microbiological activity, and hygiene issues.
A generally accepted guideline is as follows: For hand-harvested grapes, the press should be completely filled within three hours of harvesting the first grapes, if possible; alternatively, the grapes should be stored in a cold storage facility until processing. For machine-harvested grapes, the press should be filled within one hour. These time frames are not universal standards. In cases of high temperatures, damaged grapes, or varieties that are particularly sensitive to oxidation, a tighter schedule is required.
Practical Recommendation: Before the harvest, you should not only calculate the throughput in metric tons per hour. For each batch, you must also take into account the arrival time, the start of filling, the planned program, emptying, cleaning, and the available must tanks. A small time buffer is advisable, but a grape backlog generally is not. A grape buffer is only advisable during the maceration of aromatic varieties or when processing chilled grapes.
The more the grapes are compacted, crushed, or heated in the container, the sooner juice leakage, oxidation, and microbial changes begin. Therefore, transportation must be tailored to the grape variety, harvest method, temperature, and intended wine style. Sensitive grapes or those harvested when warm benefit from smaller, well-ventilated containers and short transport distances. Large containers are only advisable if compaction and juice stagnation can be reliably prevented. Additionally, the longer the transport distance, the smaller the transport container should be.
Champagne demonstrates how consistently this principle can be applied to achieve a narrowly defined quality goal: There, whole grapes must arrive at the pressing facility intact; transport crates must quickly drain any juice that leaks out; and pressing must begin as soon as possible after the harvest. These rules do not automatically apply to every winery, but they illustrate the heart of the matter: Transportation is already part of the must-making process.
The best way to the press is the shortest one. Direct feeding or gravity feeding are more cost-effective than a long chain of augers, pumps, hoses, and transfer points. Every additional meter of hose, every bend, every difference in elevation, and every abrupt transfer point increases mechanical stress. This does not mean that pumps are ruled out entirely. However, they should only be used where necessary, with routes that are as short as possible and generously sized, and with gentle pumping technology.
The drop height should also be kept as low as possible. During filling, the press tank should not be rotated simply to accommodate more grapes. Such emptying or compacting rotations generate additional shear forces even before the actual pressing begins and make clean fractionation more difficult later on. The press should be rocked back and forth only slightly to optimize the fill level.
A press should be filled with the recommended amount in a single operation. Overfilling hinders juicing, lengthens the cycle, and requires more frequent loosening of the pulp. Filling the press with significantly too little pulp also alters the pressure distribution and can lead to unnecessarily intense extraction. Therefore, the key is not to fill the press with as much or as little as possible, but to stay within the recommended operating range for the specific press.
The implication for investment and harvest planning is clear: a larger harvester is not automatically a better harvester. The right capacity is one that can be operated quickly, completely, and consistently in line with the actual harvest flow. Capacity planning should therefore be based on representative harvest days.
Before the first actual pressing phase begins, the must produced during filling needs time to drain off. This “run-off” is a separate fraction and should not be inadvertently mixed with later press musts. After that, the following applies: Build up pressure slowly and in stages, maintain each stage for a sufficient amount of time, and monitor the flow of must. The juice flow should be as steady as possible and without interruptions. The goal is not the fastest increase in pressure, but rather a flow that is as steady as possible and adapted to the press’s juicing system.
High pressure is not an indicator of quality. As extraction increases, factors such as turbidity, phenolic content, acidity, pH, color, and susceptibility to oxidation change depending on the grape variety. An industrial-scale study showed that, with higher juice yields, pH, turbidity, color index, and phenolic parameters tended to increase, while titratable acidity decreased. The exact extent of these changes depended on the grape variety and pressing conditions. Higher pressures require more mechanical agitation.
The purpose of loosening the pomace is to make it suitable for juicing again—that is, to create pathways for juice flow. It is not an additional crushing step. If the pomace is loosened too early or too frequently, the berry skins and seeds are subjected to greater shear stress. At the same time, following decompression and rearrangement, a new surge of phenols and oxidatively stressed must may occur.
Recent studies on Pinot Noir and Pinot Meunier show that significant changes in quality occur not only at a certain volume but especially after pressure relief and pomace processing. The practical conclusion: Use aeration sparingly and then taste and measure the wine with particular care. This effect is particularly relevant when the goal is to extract as much low-color juice as possible for Blanc de Noirs.
Fractionation is not a topic specific to sparkling wine. Even with still white and rosé wines, the first run, early press fractions, and later press musts can contribute very differently to aroma, acidity, structure, color, and aging potential. Those who blend these musts immediately forgo one of the most effective ways to control quality and ensure proper must treatment without the need for later corrections.
At a minimum, the initial run and the press juice should be evaluated separately. In the premium segment, it makes sense to have several clearly defined fractions, provided there are sufficient tanks, cooling capacity, and documentation. The switching point should not be determined solely by time or volume, but rather based on must flow, taste, turbidity, pH, color, and, if applicable, dissolved oxygen. Separation based on polyphenol content would be desirable.
In this context, fractionation does not automatically mean discarding later fractions. They can be valuable for a different wine style, separate fermentation, or a later, targeted blending. The key is to first make the differences visible and controllable.
A standard pressing program can provide a reliable starting point, but it cannot replace a specific oenological goal. The pressing program must be tailored to the grape variety, the vintage, the grapes’ ripeness and health, the harvest temperature, the harvesting method, the type of press, and the desired wine. Base wine for sparkling wine requires different priorities than an aromatic white wine or a color-stable rosé.
This is especially true for automated programs or those described as “intelligent.” Many algorithms initially optimize throughput and yield. To achieve premium quality, pressing stages, holding times, pressure compensation, deflocculation, and fraction limits must be deliberately tailored to the product’s intended specifications. To ensure quality, the program should be controlled in such a way as to produce a consistent flow of must.
The most important check remains regular sampling. Color, odor, taste, cloudiness, and flow characteristics often indicate changes in a fraction earlier than a fixed schedule would. A glass placed at the press outlet is therefore just as essential as a well-organized sampling plan.
Measurements of volume or flow rate, as well as turbidity and pH, are particularly useful. When quality requirements are high, measurements of dissolved oxygen, polyphenol content, and conductivity can provide additional insights. It is important not to use the largest possible number of measuring instruments, but rather a small, consistently documented selection that actually leads to decisions.
Spilled must, warm holding areas, and hard-to-reach pipes are prime problem areas. Crates, the receiving area, the press, collection tanks, hoses, and tanks must therefore be cleaned as part of the harvest cycle. Cleaning is not a break from the process, but a planned phase of the process.
Documentation is just as important. By recording the condition of the grapes, temperature, filling time, program, pressure curve, must flow, fraction limits, analytical data, and sensory impressions for each batch, you build up a knowledge base specific to your operation. This turns a good pressing operation into a reproducible process the following year.
Pressing is the culmination of the work in the vineyard and, at the same time, the starting point for the work in the cellar. Its most important task is not to extract as much must as possible as quickly as possible. Rather, it is to bring out the grapes’ quality potential, separate them cleanly, and preserve them for further winemaking. This forms the basis for the best possible economic outcome.
Context: These recommendations primarily apply to the direct processing of grapes for white wine, rosé, and sparkling wine. For red wine, pressing usually takes place only after maceration; however, the principles of gentle handling, separate fractions, and sensory and analytical monitoring remain relevant.
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