Perhaps no single piece of equipment is more iconic in winemaking than the basket press. Even those only marginally familiar with winery equipment can see a picture like the one above and immediately identify it as a wine press.

And there are few pieces of equipment that wineries want to openly display and show to customers—pumps just aren’t that sexy. In this article we’ll take a look at some of the common features and functions of a basket press. We sell Mori Basket Presses, and have for many years, so we’ll discuss those specifically. Nonetheless, the concepts will apply to most basket presses made today.

Commercial basket presses work by pressing grapes held in a large basket. The basket is usually stainless, though food-grade plastic or wood are options as well.

Hydraulic basket presses have a large hydraulic piston with a "platen" (large flat plate) at the end. The piston pushes the platen down until it reaches the grapes. This piston is capable of generating tens of thousands of pounds of force. As this force reaches the grapes and is distributed over the surface of the platen, juice runs through the cake and out the sides of the basket. The juice collects in the tray that holds the basket and is then transferred to storage or fermentation tanks. What remains after pressing is a mostly-dry pressed-out "cake". This cake is removed from the basket, disposed of (or made into grappa, if you prefer), and a new load of grapes can be prepared for pressing.

What are basket presses best for?

Basket presses are typically compared to pneumatic membrane presses. While many facilities use both membrane and basket presses, some only have one or the other. If you’re choosing between a membrane press or a basket press as your first and only press, the choice will depend on what types of grapes you intend to process.

Because they are so gentle, basket presses are best at pressing fermented red grapes. If a winery has both membrane and basket presses, they will typically use the basket presses for their high-end, reserve red fruit and the membrane presses for fresh destemmed grapes, whole cluster grapes, or higher-volume red processing.

Pneumatic membrane presses, on the other hand, are fairly rough on fermented red grapes. Most pressing programs in a membrane press involve pressing and rotating over and over again. This is great for fresh grapes and whole clusters, but it can break up the delicate solids found in fermented grapes, which results in more lees. For this reason membrane presses are the weapon of choice for most white winemaking processes, but may be the second choice for fermented reds, where the increased lees will require extended processing—longer racking times, more filtration, etc.

Are basket presses gentle?

As previously noted, basket presses are the most gentle press available, which leads them to produce some the highest-quality juice with fewer lees than membrane presses. Particularly when pressing fermented red grapes. Although they produce many tens of thousands of pounds of force, this force is distributed over the surface of the platen. The grapes remain static and largely undisturbed, resulting in extremely clear, concentrated juice.

Are basket presses easy to operate?

Operating a basket press is pretty simple. You turn it on, set your maximum desired pressure, and press go. The press will operate with no further input from the user until the maximum pressure is reached, at which point it will stop. You can set a higher pressure, and it will continue on again. Repeat this cycle until you reach the final pressure you desire.

If that’s still too much manual intervention for you, Mori’s presses are available with several automation packages up to a PLC that allows you to program pressing "recipes" wherein you gradually increase the pressure, set the exact duration of pressing, set the time for allowing free-run juice to drain between pressure cycles, etc.

What aren’t basket presses good for?

Although they’re great at pressing fermented red, basket presses are not as good as membrane presses for pressing fresh grapes. Their advantage in gentleness is a disadvantage in this case. Membrane presses press fresh grapes, then rotate several times before pressing again. This press-rotate-repeat cycle aids in breaking up the pressed-out cake, exposing grapes that might not have been pressed the first time around.

Grapes in a basket press, on the other hand, never move. If there are some unpressed grapes stuck in the middle of a basket press, they may remain unpressed as the pressed grapes form a rigid structure that the platen can’t overcome, and pockets of unpressed grapes remain within.

There are some strategies to allow basket presses to better press fresh white grapes. Users may press the grapes as whole clusters, allowing the stems to assist in the pressing. They may also add rice hulls to fill in the empty spaces and provide more surface area for the fresh grapes to press against. Finally, they may purchase additional nylon pressing diaphragms. The nylon diaphragms also provide extra surface area to press against, and break up the cake to prevent unpressed pockets from forming. Three diaphragms are normally suitable for red grapes, but users may find they need 6 to 9 diaphragms for fresh grapes.

Nylon press diaphragm
A typical woven nylon diaphragm

In short, while you can definitely use a basket press for fresh white grapes they are typically not the first choice unless the winery has just one press.

Additionally, even the largest basket presses are only about 15 HL (~395 gallons) in capacity. That’s substantially smaller than the largest commercial membrane presses, which may feature capacities more than 5 times as much. As a result, large wineries often use basket presses for high-end reserve fruit processed in smaller lots, but they process the bulk of their grapes on membrane presses that have much greater capacities.

How do you load and unload a basket press?

If you have a must pump, pumping the grapes into the basket is easiest. A grape elevator that discharges into the basket also works great.

If you want to use forklift bin dumper to load the basket, you may need a funnel hopper that is wide enough to accommodate bins, which are usually wider than the basket.

After pressing, there are several strategies for unloading. Mori’s smaller PZ presses have a split basket, so users will split the basket in two and shovel out the pressed-out cake. Mori’s PZ FL presses sport a forkliftable tray and a basket that is lifted up and out of the way by the pressing ram. This means users can lift the basket off and use a forklift to dump the pressed-out cake. If users are concerned about processing the most grapes possible in a day, they will purchase a second tray so that it can be loaded into the press as soon as the previous one is done pressing, thereby maximizing throughput.

Final Thoughts

Our feeling is this: if you’re pressing fermented red grapes—and particularly if you specialize in reds—you need a basket press. And if you need a basket press, we can help. Reach out to us with any questions you may have. We love to talk presses.