The Successful Collector, by Julian Hitner: Wine education for us all – red wine fermentation explained

The Transformation from Grape Juice to Wine

Julian Hitner

Julian Hitner

From the Latin word fervere (meaning to boil), fermentation is the biochemical process by which grape juice is transformed into wine, and is the most significant stage in the winemaking process. It is also one of the most complicated. Though humans have known how to make wine for thousands of years, our knowledge of why grape juice can be made into wine is only a relatively recent discovery.

In popular science, much of the credit goes to nineteenth-century scientist Louis Pasteur (1822-1895), who first noted in 1856 the role yeast played in the conversion of sugar in grape juice into alcohol. Later scientists’ analyses would prove that enzymes present in the yeast cells were the active agents. Fast forward to today, and our knowledge of fermentation has never been greater—or more confusing. For wine lovers, what are the most important things about fermentation to know?

Louis Pasteur

Louis Pasteur

Let’s look at top quality red wine. After the grapes have been sorted and crushed (along with an optional percentage of destemming), they are deposited into open vat containers, usually temperature-controlled stainless steel, to be fermented into wine. At this critical stage, the winemaker will have all sorts of important decisions to take, yet one of the most consequential is deciding on what type of yeast to use in order to convert the sugar in the grapes into alcohol.

In places like Bordeaux and Burgundy, ambient yeasts are the norm. These are yeasts that are naturally present in both the vineyard and winery, and are widely believed to result in more interesting, higher quality wine. There are also many winemakers who believe that natural yeasts contribute to their wine’s distinctiveness and regional personality. In much of the New World, on the other hand, cultured yeasts are more commonly used. In parts of the world where winegrowing doesn’t have an extensively long history, these are usually more reliable than their ambient cousins, and give winemakers better control and greater uniformity throughout the fermentation process. Ask any winemaker: they’re likely to name their greatest fear as a ‘stuck’ fermentation, when not all of the sugar has been successfully converted into alcohol. However, the drawback with cultured yeasts is the potential loss of individuality and excessive alcohol levels that come with rejecting the chances of nature. When it comes to yeast, winemakers must weigh their decisions very carefully.

Tobreck - Fun in the Grape Vat

Tobreck – Fun in the Grape Vat

Just as important is the temperature range at which fermentation takes place. For premium reds and many other types of dry table wines, temperatures begin to rise very quickly once fermentation gets going. This is why temperature-controlled stainless steel vats are so useful. Aside from matters of hygiene, there are few better vessels for guaranteeing winemakers as much control over temperature management. As the fermentation accelerates, it is essential that temperatures be kept around 25-30°C, otherwise the winemaker could have a ‘runaway’ fermentation on their hands, resulting in wine of rather dubious quality.

At the same time as fermentation is underway, winemakers must ensure the proper extraction of all necessary constituents bestowed by the grapes (particularly their skins in the case of good red wine), specifically tannin, colour, and flavour. As red wine ferments, all solid matter floats to the top of the vat on account of the high levels of CO² that accumulate during fermentation, resulting in the formation of a ‘cap’ at the top of the tank. During fermentation, it is imperative to keep this cap submerged as much as possible, not for the reasons just mentioned but also to avoid overheating and the formation of unwanted bacteria.

Torbreck - Pumping Over at Sunset

Torbreck – Pumping Over at Sunset

There are several ways to accomplish this. One is the use of pumps to routinely spray the fermenting liquid from the bottom of the tank right over the top of the cap, otherwise known as ‘pumping over.’ Another is to simply insert a metal grill in the middle of the vat to keep the cap permanently submerged. An additional option involves the use of long poles to simply push the cap back down, a method known as pigeage that is still in use (albeit with lessening frequency) in Bordeaux. These days however, an increasing number of winemaking facilities are being built to accommodate the employment of ‘gravity-fed’ apparatuses. Of cap submergence, this involves draining the liquid at the bottom of the vat and transporting the liquid via elevators to the top the tank and reintegrating the wine. This means the wine is subjected to as gentle a manipulation as possible, which is nowadays considered critical to the production of premium red wine.

Once alcoholic fermentation is complete—with or without the addition of sugar, usually added to increase alcoholic content (otherwise known as ‘chaptalization’)—the winemaker must finally decide on whether or not to permit the onset of a secondary, bacterial fermentation. Known as ‘malolactic’ fermentation, this involves the conversion of harsher (‘appley’) malic acids into softer (‘milky’) lactic acids, and is highly desirable in the crafting of top quality red wine. Nowadays, most winemakers opt to coerce the onset of malolactic fermentation immediately following the completion of alcoholic fermentation by raising temperatures to around 20°C; while others still prefer malolactic fermentation to occur in barrel at some point during the maturation process. There are even those who encourage it to commence concurrently while alcoholic fermentation is taking place. In each case, the object is the same: to increase stability, complexity, and achieve a smoother sense of mouthfeel and flavour.

Clearly then, there is much involved in the successful transformation of grape juice into wine. Thanks to individuals like our good doctor Pasteur and many others since, our knowledge of fermentation has never been greater. The hopeful result? Better quality wine. Funny how end goals seem so simple when compared with the means of obtaining them.

A few of Julian’s gems for collectors from VINTAGES March Releases:

Chateau Montelena 2010 Chardonnay, Napa Valley, California: Better than recent vintages, the 2010 Chateau Montelena Chardonnay represents a superb effort by winemaker Cameron Parry. Light lime in colour, the wine offers inviting, delicate scents of green fruits, lemon custard, dried apricots, pears, mineral traces, and a hint of vanilla and nuts. Complex, boasting excellent fruit, balanced acidity (unusual in this neck of the woods), and an elegant, extremely fresh hint of pears and slight mineral- and nut-tinged nuances on the finish. Marvellous style, balance, and appeal; this will keep very well over the medium-to-long term. Now-2019.

TerraVin 2009 Single Vineyard Sauvignon Blanc, Marlborough, New Zealand: For the past several years, an increasing number of Marlborough producers have begun experimenting with oak-treated versions of Sauvignon Blanc. The results have been immensely successful. Very pale lime in colour, the 2009 TerraVin 2009 Single Vineyard version offers very beautiful, almost ‘crystalline’ scents of delicate gooseberry-infused grapefruit, green fruits, minerals, and a hint of white peaches, lemon citrus, and herbs. Complex, with extremely zesty fruit, balanced acidity, and a potent hint of gooseberries, kiwi, and orange zest traces on the finish. Remarkable vibrancy, clarity, and style. Screwcap closure. Now-2015+.

F. Tinel-Bondelet 2010 L’Arrêt Buffatte, Pouilly-Fumé, Loire, France: Representing excellent value for money by local market standards, the 2010 L’Arrêt Buffatte certainly has a lot to offer. Pale lime in colour with a touch of straw, it reveals very beautiful scents of slightly tropical pears, lemon, peaches, gooseberry traces, minerals, and a hint of white flowers. Complex, carrying sensationally zesty fruit, balanced acidity, and a crisp, refined hint of pure minerally green fruits on the finish. Terrific elegance, integration, and balance. Now-2017.

Robert Mondavi 2008 Reserve Cabernet Sauvignon, Napa Valley, California: Even better than the monumental ’06, the 2008 Reserve Cabernet Sauvignon is as close to perfect as this label has ever reached. Extremely dense black-ruby in colour, the wine is beautifully toasted, exuding stellar, surprisingly subdued aromas of currants, plums, moderate mocha extract, black cherries, blackberry liqueur, licorice, grilled herbs, forest floor, asphalt, sushi wrapper, vanilla, and spice. Extremely complex, delivering prodigious, powerful forward fruit, firm tannins, milder acidity, and a polished, full-throttle hint of plummy blackberries and mocha extract on the finish. Fabulous layering, flavour, power, and harmony; I suspect this will keep for at least two decades. Also contains 8% Cabernet Franc and 7% Petit Verdot. Now-2033++.

Inglenook 2009 Rubicon Cabernet Sauvignon, Rutherford (Napa Valley), California: The best vintage I’ve yet to taste of this impeccable label, the 2009 Rubicon Cabernet Sauvignon is akin to a tall tale of opulence, extract, and underlying harmony. Extremely dense ruby in colour, the wine is beautifully toasted, burgeoning with hedonistic aromas of chocolate, currants, blackberry liqueur, kirsch, dried blueberries, licorice, graham crackers, forest floor, fresh vanilla pods, and spice. Very complex, delivering unbelievably powerful fruit, very firm tannins, milder acidity, and an incredibly lengthy, polished hint of chocolate, plummy currants, and blackberry liqueur on the finish. Massively Parkerized, yet seemingly harmonious for the style; an outstanding outing when taken as a whole. Also contains 3% Cabernet Franc and 1% Merlot. Now-2035.

La Gerla 2007, Brunello di Montalcino DOCG, Tuscany, Italy: Surpassing most expectations, the 2007 La Gerla is one masterful, innately refined Brunello di Montalcino. Dark garnet in colour, it exhibits outstanding traditional aromas of wild savoury red cherries and plums; giving way to leather, underbrush, delicate mesquite and chestnuts, sandalwood, cedarwood, tobacco, floral elements, and spice. Very complex, delivering impeccable fruit, firm tannins, balanced acidity, and an utterly refined, exemplary hint of wild red cherries, cedarwood, and floral undergrowth on the finish. Outstanding refinement, harmony, and breed; this will last well over fifteen years. Now-2028++.

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