Rippon’s Gewürztraminer and the quandry of white wine fermentation temperatures

I opened a bottle of Rippon’s lovely 2011 Gewürztraminer a few nights ago in a small act of celebration upon having an academic manuscript accepted for publication (hooray!) As I bathed my nose in pretty peach and lime and rose notes, to my surprise, my very non-oenophile husband commented that he didn’t find it very aromatic. (I blame the tahini-miso oca, or New Zealand yams if you prefer, that he’d just noshed). Conversation ensued about white wine aromas. Conversation turned technical, as it’s inclined to do around our table (he may not be an oenophile, but my partner is unmistakably an academic and a knowledge-hound), and an interesting conundrum turned up.

Modern winemaking dogma says that white wines should be fermented at fairly cool temperatures to maximize their aromaticity. Aromatic molecules are, by definition, volatile — they can leave the liquid and travel into the air, where we can sniff them into our nostrils and bring them into contact with aroma receptors. Fewer of those volatile molecules will leave the liquid at cool temperatures than at warm ones because (to simplify), warmer molecules have more energy, are moving faster, and consequently have a better chance of flying off the liquid’s surface. Fermenting at cool temperatures, then, keeps more aromatics in the wine for you to enjoy on a later occasion rather than liberating them into the atmosphere of the winery.

Fermentation creates heat, sometimes even enough to kill off the yeast and stop fermentation in mid-stride. To keep that from happening, winemakers have a few different options. Smaller containers have higher surface area to volume ratios than large ones, release more heat into the surrounding air, and generally stay cooler. The old-fashioned solution, moving small tanks or barrels outside to take advantage of cool night-time temperatures, can work for small operations in cool places. Keeping the room where fermentation is happening cool helps, though that’s a pretty inefficient and energy-expensive option. Far and away the standard contemporary solution, the jacketed stainless steel tank, lets cellar staff dial in specific temperature programs and is near-ubiquitous in modernized operations of decent size. Near-ubiquitous, but not entirely so. Two of my favorite wineries near my old home and my new one, Eyrie in the Willamette Valley (an Eyrie pinot blanc would have been on my celebratory table if I’d had any) and Rippon in Central Otago, both do without. They’re expensive, and they also don’t fit with the low-manipulation philosophy both espouse.

So here’s the quandry. Both Eyrie and Rippon turn out deliciously aromatic whites. Neither uses sophisticated temperature control during fermentation. Both McMinnville, OR and Wanaka, NZ are coming on cool roundabouts harvest time and both operations use small tanks, but it’s still safe to say that those ferments are exceeding the UC Davis-endorsed temperatures.

Why don’t they (and every lovely white wine made before the advent of modern refrigeration) seem vapid, empty, and unappealingly burnt out? I can’t be certain. When I asked Jason Lett, winemaker at Eyrie, this question, he suggested that I do an experiment to try to find out. Having left my lab days behind me, I’m not in a position to do so (it would be a big project in any case) so I’m left to speculate.

The situation is too complex with too many variables for me to evaluate with any chance of accuracy. Yeasts produce different arrays of aromatic compounds at different temperatures, for example. But I also speculate that these wines would, in fact, be more aromatic if they were kept cooler. They don’t seem to be lacking anything, I suspect, because spontaneous fermentations, excellent grapes, and attentive winemaking are already contributing plenty of aroma in any case. A recent study (that actually concerns itself with the possibility of using non-Saccharomyces yeasts to alleviate some of the potentially harmful side-effects of fermenting at low temperatures) suggests that the microbial diversity that comes with spontaneous ferments is probably helping hold up aromatic diversity, and it’s not the only one (this excellent article on sauvignon blanc aromas points to advantages from yeast diversity, too).

In other words, I can’t help but wonder if fermenting at artificially-controlled cool temperatures is something we’re told we need to do because modern industrial practices strip aromas in other ways; that is, if we’re not compensating for less-than-ideal winemaking. Cooler fermentation might (or might not) make that gewürztraminer I enjoyed more aromatic, but it wasn’t wanting. The $15 mass-market version, on the other hand, probably needs all the help it can get.

Those oca, incidentally, threatened to steal the show from the wine. (I think the wine won, though: a bit off-dry, but well-balanced, with the sort of creamy richness I look for in a gewürztraminer and, of course, plenty of peach-lime zest aroma.) Should you catch some of these unusual almost-potato tubers in the market — or, like me, should the house you’ve rented have a patch of them resident in the back garden — here’s a suggestion. North American yams take well to the same treatment.

Tahini-miso oca for four (or two plus leftovers)

1 lb (450 gm) oca, washed and cut into approximately 1″ pieces if large

2 tbsp tahini

3 tbsp white or barley miso

2 tsp butter

~ 1 tbsp fresh thyme leaves, if available (or substitute 1 tsp dried thyme)

Heat about an inch of water in a medium-sized saucepan over moderate heat until steaming, then add the oca, cover, and steam over moderate heat for about 10-15 minutes or until tender all the way through when prodded with a fork. While they’re cooking, combine the miso and tahini in a small bowl. (The purpose of doing this, rather than just adding both to the pot individually, is to help the miso mix more easily into the oca. If you’re really interested in saving dishes you can just do the former, but you may end up with miso-lumps.) Drain any remaining cooking water from the pan. Add the tahini-miso mixture, the butter, and the thyme and toss gently until all of the tubers are coated in the sauce. Serve immediately.

11 thoughts on “Rippon’s Gewürztraminer and the quandry of white wine fermentation temperatures

  1. Hi Erika

    We discuss this issue a lot with my third year wine students, because it highlights complexity of the winemaking system. So I hope you don’t mind a rather drawn out answer.

    The first point I would say the commonly held idea cool ferments smell better is reduced losses due to volatility is often over-stated. Yes volatile aromas are volatile, and they will be lost more at increasing temperatures. However this will be compounded by the fact that the expulsion of CO2 by the ferment is also increasing as rate of fermentation increases with increasing temperature. So we see some synergy with respect to aroma loss.

    However another important factor is the one you allude to with respect to yeast species. At different temperatures yeast metabolise differently leading to different aromas. Warm temperatures can bring out sweaty-thiol and heavy sulphide aromas, while cool temperatures lead to more fruity esters. So on average the cooler the temperature the more appealing the aroma is, until the point where cool temperature slows yeast metabolism to problem levels.

    So how can producers make aromatic whites without temperature control? I often turn to an area I call “evolutionary oenology”, where we use history to examine winemaking concepts. In the past some of the most desirable wines in the world were considered to come from the Mosel. It best shown in historic pricing when Mosel was rated more highly than Bordeaux (see One could speculate that those historic Mosel wines were desirable because of their aromatic intensity (which the still exhibit to this day), which other white wines could not match. The Mosel is a cold climate, requiring heavily sloped vineyards near the river to capture maximum sun, reflected light and latent heat from the river to ensure ripening. These vineyards are hard to farm, and there are limits to what 1-2 people can handle, which results in hundreds of small family wineguts. This means wine inventories in cellars are small, so small oak foudre/barrels are the common. As grapes are harvested late in the season, the weather is decidedly brisk and these small barrels naturally stay cold. Then combine this cool environment with non-inoculated ferments and its not unexpected that ferments remain cold through ferment. This results in favourable aroma production and low aroma losses from the either CO2 or temperature. These are aromatic wines, which face little competition from warmer location.

    Now warmer locations, the weather is conducive to growing large amounts of grapes. These vineyards produce large volumes of juice, which need to be stored in large tanks. As these grapes are going to be early ripening, they are picked in the warm days of early harvest. Warm air temperatures and those large tanks, result in a ferment that is warm and fast and the wines are decidedly different to that of the Mosel. Of course making the problem worse is a classic “feedback loop”, where high temperatures, result in faster ferments, which consume more sugar and release more heat, resulting in faster ferments….. Before you know the ferments are warm or hot, biomass exceeds nutrition levels (which are usually lower in high yield, warm climate, higher maturity fruit) and fermentation becomes less interesting and often less present. These wines are like chalk and cheese when compared to the fruity aromatic intensity of the Mosel. However when you throw refrigeration into the equation, the winemaker takes control and can start to deliver Mosel like qualities in locations outside those cool regions. In Australia the advent of cheap refrigeration and economically grown grapes created a boom in Aromatic wines, which allowed people with to enjoy styles of wines they previously could not obtain or afford.

    This is a simplified version of course where I haven’t considered the role of politics, economics, immigration, marketing, architecture, scientific inquiry, technological development on aroma.

    However this post is already too long so I will leave it with the idea that the wine styles you mention are taking advantage of conditions not far removed as the old winemakers of the Mosel and your enjoyment of them is not that unusual.

  2. Hi There,
    I read with interest your article on fermentation temperatures.
    I make Sauvignon Blanc in New Zealand and always strive to create complexity and extra layers of flavour.
    We have cooling on our tanks and so I am able to maintain some ferments at around 15 degrees Celsius (cool), while others we let ferment into the early 20’s (warm).
    I am not a scientist, but what seems to happen, is that the lower fermentation temperatures accentuate thiol based volatiles. But when we ferment at higher temperatures, we sacrifice thiols but gain in ‘minerality’. In my view, the combination of the two make for a much more interesting wine and a longer experience on the palate.

    Kind Regards,
    Carl Fraser

    • Indeed, Carl. If you have a copy of Jamie Goode’s The Science of Sauvignon Blanc around, I think that he reviews a few studies pointing to exactly that conclusion.

  3. Interesting recipe, where did it come from? (Japan presumably but any reference? I’m a very keen cook)

  4. Hi Erika,
    I make wine in South Africa and in Alsace. In order to get a good aromatic expression on Gewurtztraminer, we let the ferment temp peak at over 24 deg Celsius. My barrel ferments in SA often get to 28 degrees. While there is a loss of very primary fruit, I feel there is a big gain in other fruit aromas. I think it depends on the nature of the aromatic precursors in the must. Higher temperatures favour glycosidas activity which can release aromas that would be otherwise bound to sugars in the must. I get great aromas from Roussanne. A friend makes wine from the same block in the reductive, cool Sauvignon blanc style, and the wine is decidedly less aromatic. I think it comes down to knowing the grapes you are working with. The ‘standard’ recipe was a great leap forward for certain styles of wine, but it is too ruthlessly and ubiquitously applied.

    • A very interesting point, John. “Winemaking dogma” inevitably oversimplifies what, inevitably, are complex situations and the result is, as you’ve noticed, less complexity in wine styles on the whole. I’ll be looking for research (maybe out of Stellenbosch?) on the aromatic trade-offs of higher temperatures; your rationale about glycosidases makes sense. And I’ll hope for the chance to come visit and see for myself sometime!

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