Winegrowers Supplies  -  an article from the USA.

Crushing and de-stemming are two different, albeit related, operations that are usually combined in a single piece of machinery. The most common crusher is a pair of interlocking lobed rollers. Crushing makes sure every berry is broken open, thereby releasing the juice from the grape, making it available for fermentation. De-stemming is the separation of the berries from the stems. Grapes can be crushed, de-stemmed, or both crushed and de-stemmed. Additionally, grapes can be crushed first then de-stemmed or de-stemmed first then crushed.

Thirty years ago, most California wineries used crusher/de-stemmers, which is to say that the grapes were crushed then de-stemmed. Although, it was felt that crushing first tended to release undesirable "green flavours" into the wine, particularly if the stems were incompletely lignified (had not become woody) at harvest (research into this point tended to be inconclusive, with some researchers arguing that the juice-to-stem contact was much too short in duration for flavour components to leach from the stems to the must). This caused many wineries to replace their crusher/de-stemmers with de-stemmer/crushers.

More recently however, there has been a trend away from using a crusher on all but the toughest-skinned grapes, such as Muscat and Cabernet Sauvignon. It is felt that by allowing yeasts to develop and break the skins naturally, the fine tannins can be maximized and more of the fruit character of red grapes can be preserved.

Nevertheless, most "de-stemmers" in use today are actually de-stemmer/crushers. In situations where only de-stemming is desired, either the crusher rollers are separated so that they are much wider than the berries (75 to 90 mm is typical), or the entire crusher-unit is removed. For the purposes of this article, the term "de-stemmer" refers to both de-stemmers and de-stemmer/crushers. When an emphasis is being placed on the process of de-stemming without crushing, the phrase "de-stem only" will be used.

The modern de-stemmer is really a fairly simple machine in appearance. Most de-stemmers consist of a perforated circular or semi-circular cage, and an axle to which beaters are attached is mounted down the axis of the cage. When the beaters are rotated, the berries are pressed through the holes in the cage. The stems, however, are moved down the length of the inside of the cylinder by the beaters and discharged out the end. The beaters are needed because the centripetal acceleration of the cage alone is not quite sufficient to detach the berries from the rachis. In older de-stemmer designs, the beater took the form of helical blades, but most modern de-stemmers employ beaters with chisel-shaped "fingers." Increasingly these fingers are being made with rubber tips to minimize the damage to the berries as they are being de-stemmed.

De-stemmer attributes

When comparing de-stemmers, winemakers should look for a de-stemmer that is designed for gentle fruit handling. The crusher rollers should be either removable or able to open so that berries may pass through uncrushed.

Also, if the winery processes varietals with substantially different berry sizes, the winery should look at de-stemmers with interchangeable cages and beaters so that the hole size of the de-stemmer cage can be matched closely to the berry size. The closer the cage holes and berries are in size, the fewer 'stem bits' end up in the must.
Choosing a de-stemmer that fits your winery's rate and mode of operation is also important. De-stemmers operate best when they are almost at capacity. In general the de-stemmer should be sized according to the size and frequency of the bins and gondolas delivering grapes to the winery, it's best to stick to de-stemmers with removable crusher-rollers if processing these varietals. Otherwise, consider foregoing purchasing a crusher and make do with a de-stemmer alone.

Cage size and interchangeability: The varietal selection also plays a large part in determining which de-stemmer is best for a given winery. Wineries making wine from a wide selection of varietals will need less "surge capacity," in the form of a larger de-stemmer, than a winery specializing in a single varietal since different varietals tend to ripen at different rates, thereby spreading out the winery's harvest. Similarly, a winery receiving grapes from a lot of different microclimates will tend to have more spread out harvests for each varietal than those drawing from more homogeneous vineyards.

One would think that certain de-stemmers would match certain varietals better than others. To some extent this is true. Gentle de-stemmers, like the Armbruster, tend to be favoured by wineries that specialize in delicate varietals like Pinot Noir or Viognier. However, a de-stemmer that works well for Pinot Noir will probably be just fine for Cabernet Sauvignon.

The berry size for the varietals to be de-stemmed should determine the hole size for the de-stemmer cage. Ideally, the holes in the de-stemmer cage should be just slightly larger than the berries to be de-stemmed. Too small and berries will be ejected with the stems; too large and there will be more stem bits in the must.

In an ideal world, a winery would have two or three de-stemmer cages with differing hole sizes so each could be de-stemmed optimally. Depending upon the winery's target price-point, and the amount of small-, medium- and large-berry varietals to be de-stemmed, this may or may not be feasible. In cases where it is not possible, the winery should consider a de-stemmer set-up that is optimized for the winery's flagship wines rather than trying to find a compromise solution.

For example, if a winery makes a high-end Cabernet Sauvignon, mid-to-high-priced Chardonnay, a mid-priced Merlot and a value-priced Sauvignon Blanc (made with about 5 % Semillon), the winery should get a de-stemmer with a removable crusher and a de-stemmer cage with 18 mm or 22 mm holes. The 22 mm holes are admittedly a little on the small side for processing medium-sized Merlot berries, and certainly the large Semillon berries will be inefficiently de-stemmed; however the "money" in this example lies with small-berry varietals. In this case, the winery should avoid the temptation of getting a de-stemmer cage with a little bigger holes (25 mm tends to be a more usual Merlot size). The slight gain in yield for the Merlot would be more than offset by getting more jacks in the Cabernet Sauvignon, Chardonnay and Sauvignon Blanc.

The "aromatic" varietals, such as Muscat, Semillon and Symphony, all pose an interesting quandary. These grapes all have pretty large berries and tend to be slimy enough that whole cluster pressing doesn't work very well. You can't really just bypass the de-stemmer unless you are willing to accept a very long press cycle and a low yield.

To make matters worse, these aromatic varietals tend to be used as blenders or for small-production specialty wines. This means that they are normally a pretty small part of a winery's operations. Therefore, most wineries can't justify the expense of separate crusher cages just to process these varietals. However, if the amounts are really small, say less than 10 tons per year, I would be tempted to get a separate micro-winery crusher/de-stemmer like the venerable Zambelli, which should be less expensive than a second or third de-stemmer cage for the winery's main de-stemmer. This gives the winemaker a little more production flexibility at a price comparable to, or less. De-stemmers range from the one-ton per hour Delta E1 up to the 70 ton per hour Delta E8. This pretty much covers the entire industry. The selection of the right de-stemmer is as much a matter of economy as it is one of capacity. Very small micro-wineries on a really tight budget will probably stick with the tried and true Zambelli or Enoitalia as they offer adequate crushing and de-stemming with the least expensive capital outlay. However, if the business plan allows for a little more capital investment, and if the winery is considering the larger Zambelli and/or Enoitalia models, smaller wineries should also consider the CMA, Enoveneta, TEM, Healdsburg and Mori de-stemmers. Small wineries with more generous budgets will also want to look at the Armbruster, Amos, Della Toffola, Magitec, Puleo, Rauch and Vaslin-Bucher de-stemmers. These de-stemmers tend to cost a bit more but are favoured because of their delicate de-stemming by winemakers producing wine for higher price-points.

Mid-sized wineries (50,000 to 500,000 cases per year) will most likely find their best match from among the Armbruster, Amos, Della Toffola, Magitec, Puleo, Rauch and Vaslin-Bucher de-stemmers. These de-stemmers provide a good balance between operational capacity and gentle fruit handling. Additionally, the larger Healdsburg de-stemmers have the reputation of being the iron horse of the industry and, as such, Healdsburg de-stemmers can be found at many U.S. wineries.

Since de-stemmers get cheaper, per ton processing capacity, as they get larger, large wineries (more than 500,000 cases per year) are more limited by capacity than budget in this case. Della Toffola, Diemme, Healdsburg, Magitec, Puleo and Vaslin-Bucher all make high capacity de-stemmers with more than 60 tons per hour capacity. Additionally, large wineries should consider de-stemmers with CIP (Cleaning In Place: Equipment with CIP has been fitted with internal wash-down sprinklers so that water, or other cleaning solutions, can be recirculated in the equipment without removing exterior panels or otherwise dismantling the equipment).

Used properly, CIP can decrease cleanup time and increase sanitation efficacy. Incompletely or improperly cleaned crush equipment is a primary infection point for wine spoilage micro-organisms, particularly Brettanomyces. CIP systems would most likely benefit large wineries since they are making the most wine on the biggest equipment with the smallest crew (for the number of gallons produced).

Additionally, any winery looking at after-crusher sorting should probably look at the Scharfenberger Euroselect. The de-stemmer was actually designed to be configured so that the initial sorting can be made by the de-stemmer itself. Its incline design also means that the berries can exit the de-stemmer directly on to shaker tables for further sorting. The Euroselect is the first really radical new approach to de-stemming that the industry has seen since the invention of the current centrifugal de-stemmer designs were introduced. If this design proves robust over the long term, the Euroselect could change the look of the winery crush-pad.

Interestingly, although there are trends linking a certain varietal to a certain de-stemmer, such preferences are not as crucial for most varietals as is the need for matching the cage hole size to berry size, winemaker style, or de-stemmer capacity to winery processing tempo. That said, winemakers working with thin-skinned red varietals like Pinot Noir tend to prefer de-stemmers that have a reputation for being exceptionally gentle. Producers of thin-skinned white varietals tend to forgo de-stemming altogether and press whole clusters.

Certainly, with its large installed base, the Vaslin-Bucher Delta series is something of a market leader, but the very success of so many other de-stemmers that compete directly with the Delta suggests there is a model and combination that fit the needs of most any winery.

Thus by taking into account the degree and type of handling desired, de-stemmer interchangeability options, cage and hole size, current winery operations, varietals used and price, you should be well on your way to joining the ranks of satisfied winemakers who have discovered just the right de-stemmer for their winery’s needs.