Destemming vs whole bunch press

summary

After picking the grapes, the next step in white winemaking is often to decide whether to separate the juice from the skins immediately by pressing whole bunches, or to let the juice stay in contact with the skins for a period of time. Whole bunch pressing is gentler and tends to produce more elegant, delicate wines with higher acidity, while destemming before pressing can release more complex, aromatic flavour compounds.

The typical choice will be between:

Whole Bunch Pressing: Preserves bright, fresh fruit flavours with minimal bitterness and a delicate, balanced profile.

Destemming: Enhances riper, fuller fruit flavours and texture, making it a bolder option suited to tropical-style whites or skin-contact (orange) wines.

Keep reading if you want more technical info, the following is from two emails taken from the a decision during our first vintage in 2022 with Quinta de Soalheiro and our fith with Rodica in Slovenia in 2024.

THE TECHNICAL INFO - malvazija in slovenia

“Malvazija felt perfect for this vote as it can produce a range of styles from light, crystaline and delicate right up to a deep orange. In hindsight, though I was delighted with the winning decision to destem and crush, as pressing whole bunches of Malvazija, which I later found out is notoriously difficult to press, would have been nigh on impossible with our old-school wooden basket press. Yields would have been tiny - it makes sense that skin contact was traditionally the only way to make Malvazija before more powerful pneumatic presses came along.”

Whole Bunch Pressing

Method: Whole bunch pressing involves pressing the entire grape cluster, including stems, without prior destemming or crushing. This gentle approach limits the extraction of phenolic compounds from the skins, seeds, and stems.

Impact on Wine: Whole bunch pressing can help preserve the freshness and clarity of Malvazija's fruit flavors. It allows the more delicate flavours to shine through without being overshadowed by excessive tannin. The gentler extraction helps maintain a lighter, more delicate fruit profile, emphasising citrus, floral, and orchard fruit notes typical of Malvazija, while retaining some of the grape's natural acidity.

Flavor Profile: Expect a wine with bright, fresh fruit flavors—such as citrus, green apple, and pear—alongside a clean, elegant finish. The stems also contribute to a subtle herbal or green edge, which can add complexity without overpowering the fruit. Whole bunch pressing is ideal if you want to highlight Malvazija’s purity and vibrancy.

Note: If you opt for whole bunch pressing you will eliminate the possibility of an orange wine as there will be no skins in contact with the juice

Destemming

Method: Destemming involves removing the grape stems before crushing the berries, which exposes the skins and seeds to the juice. This method allows for more contact between the juice and the grape solids, leading to greater phenolic extraction.

Impact on Wine: Destemming can intensify the fruit flavors, producing a richer, fuller-bodied wine. The increased extraction can enhance the ripe tropical and stone fruit notes—such as peach, apricot, and melon—while also adding more structure and tannins. However, this method comes with the risk of extracting bitter compounds from the seeds and skins, which can add astringency and diminish the freshness of the fruit. Additionally, acidity might decrease, making the wine feel heavier and potentially less balanced.

Flavour Profile: The resulting wine will have bolder, more concentrated fruit flavors, with a riper and more robust profile. Expect deeper stone fruit, honeyed notes, and possibly even hints of dried fruit, depending on the ripeness of the grapes. The wine will also have more tannic structure, which will enhance complexity and improve the texture, depending on the balance achieved.

Orange Wine Option: If you choose extended skin contact with destemmed grapes, you can produce a fuller-bodied orange wine. This style would exhibit more pronounced tannins, a complex array of fruit flavors ranging from fresh to dried, and a deeper color. The phenolics will add texture and structure, making it a more distinctive and bold wine compared to the more delicate version from whole bunch pressing. However, a vote for destemming does not guarantee an orange wine—the length of skin contact is key, and just a few days can still result in a white-coloured wine.

“The detail we gave in Slovenia I think perhaps gives the readers a better idea of what to expect from the two options, whereas in Portugal we got into more technical detail. For example, I’d say the impact on acidity and viscosity is negligble but the science is interesting”

THE TECHNICAL INFO - alvarinho in POrtugal

Flavours

Remember the phenols we talked about in the last email? The amount and type of interaction of juice with skins affected both wine total phenolic concentration and phenolic composition in the final wine.

Whilst the phenolic concentration will increase, it also increases the risk of more bitter, green and astringent flavours, especially if you choose to destem because the seeds will be exposed. Even though the machine intends to keep the berries whole, the berries will be partially crushed and open up exposure to the seeds. The seeds have particularly bitter qualities we don’t want and none of the aroma compounds that we do.

Acidity

You lose a bit of acidity with pre-maceration too, a little bit of that freshness will go along with the protective environment of a higher acid (lower pH) environment. The exact reasons will hopefully be another thing to be covered in our second year but the scientists among you may understand this; the higher levels of potassium ions extracted enhance potassium bitartrate precipitation, reducing tartaric acid concentration.

Viscosity

Lowering phenolic concentration may also result in wines of lower perceived viscosity. Therefore, getting more phenols into your wine will increase the weight and mouthfeel.

Oxidation

Enzymic oxidation happens the minute we destem or press the berries. This is what happens if you cut an apple open and leave the cut surface in contact with air. As with apples, there is an enzyme present in grapes called polyphenol oxidase (PPO). Protecting the must from oxygen by pressing as whole bunches will preserve fruity compounds like esters, but destemming (and certainly maceration) will let the juice oxidise and turn slightly brown, although it will clarify during our next step and the fermentation. When these phenolics oxidize they then fall out of the must it protects the wine later in its life. The former approach preserves fruity aromas, but also the phenolics, which makes the wine fragile later in its life, and less likely to age well.

Browning by PPO is not always a bad thing with foods either, the brown colour of tea, coffee and cocoa is developed this enzymatic browning.

Colour

This isn’t really that significant so I wouldn’t include it in your thought process but we thought it might be interesting. If we macerate the wine for an extended period of time we will start to get a darker colour. Not an orange wine, though, that would involve a fermentation on the skins and maceration for a few weeks after. We’ve only tried one orange Alvarinho before, and without naming names, those who attended some of our early Alvarinho tastings will know that it doesn’t always work. This is why we have limited the maceration period to 10 hours and only before fermentation.

The temptation of creating a wine the same colour as our logo couldn’t convince us to make an orange wine.

Volume

Another FYI thing. If we destem and crush the grapes, it becomes a lot easier to extract the juice, resulting in a higher yield even at a gentle pressing pressure. Additionally, you can fit a lot more grapes into the press, which will also reduce the number of press cycles you might need to, reducing the amount of time the grapes are exposed to the elements.

“Skin-contact is not so typical in Alvarinho, although of course some excellent examples exist. Looking back, it’s amazing how much has changed in a few years, particularly with regard to orange wines in the UK, I wouldn’t approach this topic with the same trepidation I did here in 2022.

In Portugal, susbcribers decided to go classic. As we have made more wines, I feel subscribers are becoming more adventurous, albeit often liking to stay close to the typical wines of the region. I’ve learnt to never guess which way the vote will go though, I always get it wrong!”