Stems, Crushed Grapes and Pressing

Either I did not properly pick up on some distinctions early on in my studies or people were using the terms “crush” and “press” pretty much interchangeably, so I have since had to straighten out what all this means. My confusion has arisen perhaps because in times past the machines that destemed the grapes basically could not do this without also puncturing the skins of the grapes to a significant degree. What you got was a mush of broken berries and juice. So if one was going to remove the stems one had to accept that a lot of juice would start to flow out of the berries immediately, in the case of white grapes for the short time the grapes are in the press machine itself as the pressing was taking place or in the case of red grapes in the fermentation vessel. There was in practice no option to destem and retain intact (‘whole”) berries (absent desteming by hand, which was not practical in the past but with todays higher prices a few are willing/able to do this).

Today these destemming machines are more gentle and so, given one wishes to destem, one still has the option whether or not to retain intact berries or partially crush them (puncturing the skin of the grape) subsequently. As I understand it, modern machines can remove the stems while leaving more than 80% of the berries whole. Some are even more effective in retaining whole berries. One has only to inspect Roberto Conterno’s machine to appreciate how sophisticated these instruments have become.

For White Wines. To be clear, the issue whether to destem is not as important for white grapes as it is for reds. Today, most makers of white burgundy simply toss the grape bunches into the press, stems and all. But there are some nuances here.

Since it can take perhaps four hours to perform the pressing of white grapes,  the winemaker may want to give the juice the benefit of some skin contact during this period and so partially puncture the skins at the start of the pressing by crushing the grapes - a process in France called "foulage".  Though there appears to be no universal agreement on the topic, foulage may result in a must with slightly higher total acidity. This process - crushing the grapes prior to putting them in the press - also allows the grapes to be "pressed" more quickly if that is the objective - and, importantly, at lower levels of pressure since the skins are already broken. It may also be that the few hours of skin contact during the pressing helps reduce the risk of later oxygenation if the juice, enriched by a higher level of phenolic elements, is allowed to settle a short while after the pressing. What you lose by crushing the grapes in advance is a “purity” of juice that comes from pressing whole berries.  The proponents of not crushing white berries before putting them in the press believe that crushing these grapes releases more solids from the grapes into the juice, which may make for a wine of less finesse and require management of these sediments later. Many influences factor into the decision whether or not to crush white grapes. It is my understanding that invariably in Burgundy white grapes are today not destemmed - they just go into the press stems and all. So the grape berries are presumably whole. Only exceptionally are the skins crushed before the grapes are put into the press. But the point I want to stress in this post is only that in the past that decision was taken away from the winemaker if he destemed - the grapes would be crushed by the destemer. Today they are not. So there is more choice/control today in deciding in which direction to go.

A reason for retaining the actual stems is that apparently these stalks will create channels or air pockets through which juice can easily flow. So that juice, during its passage out of the press, is in less contact with the skins of other berries than if these air channels were not to be present. Thus the extracted juice is very clean because it has had less contact with phenolic components of other grapes while in the press. This is the approach taken in Champagne.

For Red Wines. The red wine maker today similarly has the option whether or not to ferment with initially crushed or uncrushed berries in the fermentation vat.  Leaving some berries whole allows for these berries to start the fermentation process intact - a type of intercellular fermentation. This is thought to give additional aromatic complexity.  To be clear this is not full on carbonic fermentation. There is no flushing out of the oxygen from the fermentation vat. But the intact grapes release juice (and thus sugar) only when the skins break down - and this takes about two days. Intact grapes that undergo this intercellular process swell and the skins split after a couple of days. By this time there alcohol has reached only about 2%. If for some reason the skins haven’t broken down after a few days some winemakers will perform some foot treading or batonnage to break up some of the skins. Some crush some berries only and place these at the bottom of the vat. As these grapes at the bottom of the vat undergo fermentation in the presence of oxygen and yeasts work to turn the sugar to alcohol, this fermentation also produces C02, which to some extent pushes the oxygen out of the vat for the still intact grapes higher in the vat. But nobody wants too much of the “carbonic” flavor that comes from full intercellular fermentation. What you want is the added complexity. The trend in Burgundy of late has been to leave a good portion of the berries whole.  This in turn creates some difficulties in assessing the progression of fermentation since sugar is released only over time as these berries individually breakdown and release juice. Dominique Lafon has stressed this difficulty.

For completeness, full carbonic maceration involves flushing the air (and thus the oxygen) out of the fermentation vessel, then adding whole berries and sealing the vessel closed. Normally the actual stems are included, because historically this was the only way to assure the beery skins were not broken. These berries experience two or three days of intercellular fermentation than swell and the skins then break. At some time thereafter the grapes are pressed and the fermentation can be completed if necessary with the juice alone ie no longer in contact with the skins.

You can of course destem, put whole berries into the vat and then include back some or all of the stems. Jean Marie Fourrier I believe does this. Some - like Sylvain Pataille as I understand it - destem and then crush the grapes to the desired degree as a separate process. There are numerous variations.

The message in this post is that as a definitional matter the term desteming should mean simply removing the stems - without any inference whether the grape berries are to be crushed or not, which is today an entirely independent decision.  And "crushing" grapes is absolutely not the same as "pressing" grapes.  It took me too long to figure this out !

There are of course several types of presses.

I commend the podcast # 416 on Levi Dalton’s “I’ll drink to that” website by Erin Scala on the subject of desteming and a May 2020 “Zoom” Session on Jasper Morris’s website InsideBurgundy.com