My Round: Technology in the bottle

In this new regular column, environmentalist and academic Dr Timothy Krantz will introduce one of his life’s main passions – the technology of drinks production.

'I am tasting the stars!' 

Thus proclaimed Dom Perignon (1639-1715) upon the discovery of sparkling wine. Appointed the business manager and cellar master at the Saint-Pierre d'Hautvillers monastery in the region of Champagne in north-eastern France at the age of 29, he found that by inoculating 'still' wine with yeast and sugar, re-corking, and then opening the bottle later, one made it explode with tiny carbon dioxide bubbles as the yeast converted the sugars into alcohol.

Perignon is also credited for adoption of a cork closure – replacing the dollop of olive oil and hemp-plugs used to seal the bottles in the Champagne region – and for the practice of blending Pinot Noir and Chardonnay grapes. Perignon's effervescent beverage established such renown that it became the libation of the French nobility, to the degree that Louis XIV drank it almost exclusively – and we all know what happened to him!

The process of making sparkling wine has been elaborated over 350 years in some very ingenious and innovative ways. The chef de cave selects a blend of still wines. Traditionally, the cuvée was produced solely from the indigenous varieties of the region – Chardonnay, Pinot Noir, and Pinot Meunier – although many other varieties of grape are now used to make a wide array of delicious bubblies. The still wine is typically fermented in stainless steel tanks, although other vessels may be used. The purpose is simply to complete the initial fermentation – not to impart 'oak' or other complex flavours to the still wine; and then the latter is removed from the tanks, filtered, and bottled.

At this point, the natural grape sugars have largely been converted to yield a low-alcohol still wine; so an additional amount of sugar and yeast is added to the bottles to promote the secondary fermentation. The living yeast breaks down the sugar into ethanol and releases carbon dioxide according to the basic formula:

C6H12O6  >  2C2H5OH + 2CO2

As long as fermentation was accomplished in open vats, this was not a problem, but now the CO2 is contained in the enclosed bottle, the vintner becomes a potential bomb manufacturer! Internal pressures of over six atmospheres (as much as 88lb/in2) would cause the relatively flimsy bottles of the times to violently explode in their racks!

It was not until another Frenchman, Jean-Antoine Chaptal, calibrated the proper dosage of sugar to add without explosive results in 1801 that the vinification of sparkling wines was somewhat tamed. Other technological improvements in bottle manufacture, pioneered by English glass-smiths, produced sturdier bottles that could withstand these extraordinary pressures. One of these design improvements was the 'punt' – the thickened concavity at the bottom of the champagne bottle which helps distribute the internal force.

After the secondary fermentation is complete, the dead yeast and other residues remain as a sticky sludge at the bottom of the bottle. The question of how to remove the unsightly goo resulted in the process of remuage or 'riddling'.

The bottles are inverted, bottoms up, in a rack at a 45-degree angle. The 'riddler' (I picture Batman's nemesis) smilingly shakes and turns the bottles every few days by hand, slowly increasing their angle of repose over six to eight weeks until the bottles are fully inverted, allowing the sediment to settle in the neck of the bottle.

Although many sparkling wine manufacturers still undertake this laborious process by hand, some vintners use a computer-automated 'gyro-palette' that gently shakes and rotates large palettes of ~500 bottles into their inverted position in just a few weeks, cutting the remuage time by four and putting riddlers out of work. 'Curses, Batman! Foiled again!'

The bottles are now upside-down in their racks. The necks are frozen in trays of brine or glycol, and the ice-plug containing the sediments is disgorged – sometimes explosively. The gap left from the removed plug is topped off with a dosage of reserve wine and, 'Voila!'. The final product is corked, wired and wrapped to contain the pressurized contents. The dressing of the champagne bottle evolved from a simple twine-wrapped cork to prevent premature discharge, to a wire guard protected from gnawing rats by a pewter or tin foil wrap.

The 'disgorgement' process of removing the yeast plugs, refilling with dosage, corking and wrapping is a wild and chaotic experience. It is like a cross between a locker-room celebration and a war zone, with caps and yeast plugs popping like a 21-gun salute and champagne flowing copiously. Watching it, I found that I needed both hands to defend myself from flying yeast missiles, and the few notes I was able to jot down were quickly blurred with wine spillage...

Today's smart-dressed bottles, with their colourful wraps and labels, are much more than pretty packaging. The discriminating oenophile can read a lot in the label: the vintner (the producer), the vintage (year of production), varieties of grapes used (usually a blend), the sweetness to dryness (demi-sec, sec, brut, extra sec).

Most importantly, I look for the phrase 'Methode Champenoise', 'Traditional Method', or 'made and fermented in the bottle', as opposed to non-traditional methods, such as artificial injection of CO2 directly into the wine (like carbonated sodas) or via the Charmat method.

Developed by Eugene Charmat in 1907, the Charmat method involves secondary fermentation in a pressure- and temperature-controlled autoclave, allowing for processing the wine in bulk. The sediments are removed by isobaric filtration and centrifugation.

In the 1891 Treaty of Madrid, France reserved the exclusive right of restricting the 'Champagne' label to sparkling wines of that region. Thus, Italian sparkling wines are called 'spumantes', Spanish sparklers 'cava', and all others simply 'sparkling wines'.

Armed with this new knowledge, the reader can find good sparklers for 20-30. My suggestion is to read the labels carefully, look for 'methode champenoise' and other specific labelling – the more specific the better, and enjoy!

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