Inquiring Winemaker


The Downside of a Cleaner, Gentler Crush Pad

February 2014
by Tim Patterson
In winemaking, as in so much of life, it’s possible to have too much of a good thing. A bumper crop in the vineyard is great, but over-cropped vines make lousy wine. Warmth is a fine thing for fermenting and extracting red grapes, but crank that must up to 110º F and your Petit Verdot will get deep-fried. Integrated oak is a good thing; egregious oak is a bad thing.

In that spirit, it’s time to ask whether fruit can be too clean and crushing too gentle. Crush pads across the land are sporting more and more sophisticated equipment designed to deliver perfect berries to the ferment: shaking sorting tables that eliminate every leaf, fruit fly and stray jack, optical scanner-sorters that expel any berry deemed unfit, destemmers that don’t actually knock berries loose with paddles but rather calmly persuade them to self-deport from their pedicles. The War Against MOG has gone high-tech: Robots and drones may be on the way.

The aim of all this kinder, gentler, cleaner processing is maximizing the fruit character of the eventual wine and minimizing what seem like extraneous influences, and it’s hard to argue against that. Make wine from the fruits of the vineyard, not the detritus. It’s a perfectly plausible goal; nobody wants to make wine from grape leaves and gum wrappers and earwigs, and many winemakers are further determined to banish anything that might smack of those dreaded “green” flavors and to quarantine the allegedly nasty influences of grape seeds. Sure enough, squeaky-clean fruit makes super-fruity wine.


  • Recent advances in crush pad technology--destemming, sorting, crushing--have made the process much cleaner and gentler. Maybe too clean and too gentle?
  • Rigorous sorting of whole-berry fruit may result in higher alcohol, lower acidity, higher pH and diminished complexity in the resulting wine.
  • New research illuminates the amazing diversity of grapevine microbial populations and their importance to wine quality.

But is that what this wine thing is all about? Fruit juice and alcohol? Is it possible that the various forms of junk that go into the hopper along with the grapes add something to the character of wine? If everybody’s grapes get cleaner and cleaner, will their wines taste more and more similar? Does a distinctive wine with flavors other than pure fruit maybe need a little material other than grapes in its pedigree?

Technology and terroir
I had been ruminating about this for a while when Wines & Vines staff writer Andrew Adams steered me to an article in the Napa Valley Register about the high-tech crush pad technology being deployed at Conn Creek Winery in St. Helena, Calif. The setup included a gentle destemmer, a sorting table to get rid of MOG and a Bucher Vaslin optical sorter that identifies suspect fruit with a 10 million-pixel camera and then uses targeted puffs of air to jettison under-ripe/moldy/raisined losers. And as a final step, the glistening berries go into a Pellenc grape centrifuge, with which it is possible to dial in the proportion of berries that get cracked open by the spinning pressure and the proportion that stay intact at the start of fermentation.


There are apparently only two of these berry-go-rounds in operation in the United States, both at wineries (like Conn Creek) that are under the Chateau Ste. Michelle umbrella. The point of all this advanced technology, according to Conn Creek winemakers Mike McGrath and Tom Klassen, is to improve wine quality at what is already a luxury-tier brand. In the Register article, McGrath says, “Our goal is to get into the top 10 of the (Wine) Spectator within five years,” Cleaner fruit should lead to fruitier wines should lead to higher ratings.

When I talked with McGrath and Klassen, they both agreed that my question—is there such a thing as too clean and too gentle?—wasn’t ridiculous, but rather something that winemakers talk about from time to time. McGrath volunteered that sometimes a little “Cucamonga funk” could make a wine more interesting, and that even rotten and dehydrated fruit could theoretically add some complexing agents. “But,” he asks, “do you really want that stuff?” Conn Creek clearly doesn’t want much of it.

The bigger issue here, of course, is how the quest for squeaky-clean fruit squares with the pursuit of vineyard expression, regional distinctions and terroir. McGrath and Klassen oversee an extensive lineup of Napa AVA-specific Cabernets, and the winery’s tasting facility includes an AVA room where visitors can sample the range of growing locations and even make up their own blends. The best way to showcase this diversity, for them, is to get rid of the clutter and let the fruit from each spot shine through.

Maybe. But there is also reason to think that the insistence on flawless berries may have a downside, too—or several of them.

Whole-berry winemaking
The deliverable from high-tech sorting is clean, intact, whole berries. The argument for putting lots of, or maybe nothing but, whole berries into a fermentation is, first of all, that there is no danger of the crusher cracking seeds and exposing their potentially bitter innards. (That’s another column.) Whole-berry ferments also tend to be slower and longer, which can give the winemaker better control of the progression of extraction, particularly tannin extraction. The slowdown happens because at least a portion of the berries is undergoing a variant of carbonic maceration: Sugar is being turned into alcohol inside the grape by enzymatic action without benefit of yeast or oxygen.

This is the traditional method for making Beaujolais, relatively light wines with modest color, very little tannin and characteristic aromas of strawberries, bananas and such. If your goal is making a Big Red, it’s not entirely clear that you need to make Beaujolais first—unless you know that the grapes you are working with are highly tannic and in need of remedial measures. Other wise, those berries are going to have to pop their skins eventually, and those initial tutti frutti esters will be long gone after a full-scale fermentation completes.

Jim Harbertson at Washington State University, always good for a contrarian speculation or two, wonders whether a semi-carbonic phase might soften up skins and actually make them more extractable. If pressing is done early before there is much ethanol, as in Beaujolais, end of story. But if the post-carbonic skins spend a few days in the general wine bath marked by higher temperatures, rising ethanol, frequent pump overs and the like, they might well release everything they have, extruding by the end more tannin, not less.

Costs of cleanliness
I have a hunch that a good deal of the appeal of whole-berry “crushing” techniques is purely visual: The shiny, uniform fruit looks like gemstones—or as they say at Conn Creek, “Cabernet caviar”—as it rolls down the line. The parade of identical sleek, black globes makes it much easier to confirm that every hint of MOG has been expunged and every sub-standard grape extradited.

The biggest potential loss from optical sorting, says Harbertson, is under-ripe grapes, which don’t make good wine on their own but can be quite useful as a crush component. Through rigorous selection, only the high-ripeness/high-sugar grapes are left in the mix, raising final alcohol levels. Eliminating the less-ripe portion is also likely to raise the pH and lower the acidity of the must, quite possibly by enough to require adjustment in the cellar.

As for any “green” flavors that might be found in low-Brix grapes or stray stems and jacks, Harbertson notes that every fruit has within it some traces of green, vegetal flavors. Only artificial fruits are entirely fruity. He figures that even the highly sorted, super-fruity blockbuster wines have green components, it’s just that no one can taste them through the elevated alcohol.

Microbial biogeography
And then there is the question of bugs—not the earwigs, but the multitude of fungi, bacteria, spores and whatnot that hitchhike in from the vineyard with the fruit. Tom Klassen says, correctly, that the most careful sorting in the world won’t get rid of all the bugs on the grapes, and that SO2, lysozyme and, in extreme cases, ozonation of incoming grapes are more powerful weapons against microbial critters. True enough, but it’s still true that the War Against MOG significantly reduces the size and diversity of the microbial population, and that is not always to the good.

Linda Bisson at the University of California, Davis, put it this way: “For me, the key here is who is on the fruit: Excessively clean is only needed when there are bad lactics, bad acetics or bad molds on the fruit. Some of this is quite vineyard-specific and depends upon what the insect patterns are and vineyard adjacencies. If your microbiota is fine, then there is no need to be so obsessive. And yes, the microbes do contribute to a sense of place, but many winemakers want to ‘express the vineyard,’ as they say, and not have any obvious microbial signature; other winemakers are fine with the microbial signature being part of the vineyard signature.”

As I was working on this piece right after Thanksgiving, Nick Bokulich and David Mills at Davis made it into The New York Times for their research on “microbial biogeography,” the distribution of critters on and around grapevines. Though The Times’ article generated more buzz, the hard data from massive sequencing of DNA material from dozens of grape samples was published in the “Proceedings of the National Academy of Sciences.” Their research showed, first, that different wine regions consistently show different microbial DNA profiles: That is, there really is something tangible and distinctive about Napa terroir versus Sonoma or the Sierra Foothills. Second, these microbial populations vary by climate factors, vintages and cultivars: Vineyard populations morph from year to year, and Chardonnay plays host to different bugs from Cabernet. Some good bugs, some bad ones, some where we don’t have a clue.

The PNAS article is full of telling little details, many of which could translate into actual vineyard and winery procedures and decisions. Zinfandel fermentations, for example, are notorious for developing high levels of volatile acidity. Is that just how Zin is, or is it a by-product of frequently high alcohol levels? No, it’s probably because Zinfandel grapes draw a crowd of Gluconobacter, which means wineries need to pay special attention to sulfite additions and oxygen exposure.

The Mills lab at Davis has not yet traced these differences in microbial patterns through to their sensory results, and it’s quite possible that a lot of the myriad critters found on grapevines and in vineyards have no measurable effect on anything in the glass. Still, the evidence is compelling that wine fermentations involve lots more than bins of fruit and bags of yeast. What goes into making complex wines is, well, complex, and making the stew simpler may not make it better.

Guest winemaker rant
Normally I would wrap up here with a short rant about monochromatic winemaking, but instead I’ll let a real winemaker do it for me. Wes Hagen at Clos Pepe in Santa Barbara’s Santa Rita Hills certainly doesn’t go out of his way to court MOG and its influences. In the eternal Pinot Noir debate about the pros and cons of whole-cluster fermentations, stems and all, he is on the no-cluster squad, feeling you can get plenty of structure without stems and won’t have to worry about broccoli aromas. But there are limits to how clean he wants his crush pad to be:

“I believe great vineyards make great wine, and the industry is getting so competitive that I believe this movement toward sterilized, perfect fruit can suck some of the soul out of a place and a vintage. This is what I tell young winemakers all the time: Someone is always going to try to sell you something to make your wine better: an optical sorter, enzymes, tannins, new barrels, etc. Technology is not to be ignored, but it should also be designated as the distraction that it represents. Great wine represents a time and a place and the human craft that touches it. This push for over-clean fruit is a push to make wines with pure fruit character that will impress critics in blind tastings, which is not in itself a bad thing, but I do believe a w ine’s true purpose is to integrate into an experience at the table, and I find perfectly fruity wines boring. I want to taste the character, and I do believe you can scrub it off if you’re not careful.”

Tim Patterson is the author of “Home Winemaking for Dummies.” He writes about wine and makes his own in Berkeley, Calif. Years of experience as a journalist, combined with a contrarian streak, make him interested in getting to the bottom of wine stories, casting a critical eye on conventional wisdom in the process.

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