I was wondering if anyone can clue me in as to how stem inclusion in fermentation is calculated. I keep hearing percentages, but I don’t understand if this is by volume or weight, or whatever. If juice is bled off early in fermentation, is the calculation still based on initial must numbers or the adjusted numbers?
Thanks for your help on this one!
I don’t think exact measurements of stem percentage are really necessary, the idea in disclosure is to prepare you for a set of flavors and tannins that you are going to encounter which are very different then the expected fruit and oak flavors. There really isn’t much difference between 25% whole cluster vs. 33% whole cluster in the big picture. Even then, the extract depends on so many factors, like stem ripeness, soil type (which dictates grape tannins that interact with stem tannins, I have not looked in depth into how stem flavors differ with soil type), length of maceration, etc.
Perhaps its best not to worry too much about it.
I agree with Ian, but it’s just the fraction of the stems that were included. Bleeding juice has an effect on the wine, but it doesn’t change the fraction of stems that were removed.
Thank you Ian - great answer - that makes perfect sense.
Another question -
Do winemakers ever destem and then cull through the stems to find what they are looking for (more ripeness?) and then add back from there?
Yes, some do exactly that. I’ve heard of some winemakers who will freeze the stems before adding them to the must.
I’ve even heard of some folks who destem, they set a portion of the stems out in the sun to develop further (basically they go from green to brown as they dry up) and then add them back to the cold soak.
For one client who wants a certain % of whole cluster in their Syrah, I figure out this % by weight, then I destem the balance of what isn’t being left as whole cluster. For myself, I pretty much do 100% whole cluster on Syrah. It’s too much for some people’s tastes, but over time I think the stems integrate nicely with Syrah. I believe they integrate well with Pinot too, but it seems to take a much longer time.
As others have said, percentage just means what percentage of the stems are left in vs. destemmed.
I’m also a fan of whole cluster in pinot and syrah and some other grapes as well, but how well it works has myriad variables, starting with terroir and viticulture and continuing into the winery. And how well it works is of course subjective as well!
Thanks so much for the input gents!
I’ve thought about doing this, but I had a couple misgivings about it. First, I am leery of what would be growing on the sugared up stems while they dry. Nothing I’ve smelled in 3 day old stem bins has made me want to add them back, though I imagine there is a way to do it more carefully. Secondly, I’m not sure that drying green stems would achieve the same result as maturation/lignification on the vine. The analogy (and I’m not sure how apt it is) I think of is hay production; when grass is cut while green and left to dry, it has a very different composition than it would have if you waited to cut it after it browned up in the field.
I’ve also been hearing more winemakers say that they have lowered their standards on lignification of the stems that they included and still gotten good results. I followed suit this year with inclusion of some stems that I would have thought too green in previous years and am happy with the outcome.
In Burgundy, we have a good amount of stems used even without lignification. I’m a fan of stem usage but I’ll be doing less experimenting myself next year. In 09 I took a gamble on one lot and got lucky. There are too many variables in play to know the result with the variations of each harvest imr(rookie)o.
I’ve heard the components/amount of sap in the stems varies quite a bit throughout the day. So picking green stems at dawn is fairly safe, while picking at noon would give you a lot of green nastiness. Can anyone correct/explain/elaborate?
I don’t know about that, but I have heard the claim that letting the harvested fruit sit for 24 hours prior to crushing allow the cut on the stems to seal up and keep some of the sap from leaking out into the must.
I’ve heard about that, too, I think from Sean Thackrey, who I think read about it in one of his ancient books on winemaking.