Week 6 of the WSET Diploma got all geeky again and we looked at some of the different adjustments a winemaker can make to improve the final quality and balance of a wine.
Enrichment – this is where sugar is added to grape must prior to fermentation in order to increase the potential alcohol of the finished juice.
You know the old Pilsner advert, all the sugar turns to alcohol – well the more sugar you start with, the higher the potential alcohol of the finished wine.
The term ‘chapitalisation’, strictly speaking, should only be used if beet sugar is added to grape juice, not cane sugar. RCGM (Rectified Concentrated Grape Must) can also be used and is thought to be less ‘artificial’ as it is made using the concentrated sugars of grapes, however, it is much more expensive. EU subsidies used to mean sugar beet was very cheap, but it is now only marginally less expensive than beet sugar.
17g of sugar per litre roughly equates to an additional 1% potential alcohol for white wine, while it takes approximately 19g of sugar per litre to create an additional 1% potential alcohol in red wine. This is because more alcohol evaporates during red wine fermentation, as higher temperatures are used and wines are often fermented in open top vats.
Don’t think adjustments are for just for mass produced wines, the wines of Champagne are enriched almost every year.
Concentration – removing excess water from the juice to improve the balance and concentration of the finished wine. This can be necessary if it has rained during harvest and the grapes are bloated and the flavours and sugars diluted.
De-acidification – removing excess acidity from under-ripe grapes through the addition of potassium bicarbonate, calcium carbonate, expensive double salt deacidificiation (calcium carbonate and calcium tartrate-malate) or malomatic fermention.
In most ripe grapes, tartric acid is the main acid and the use of carbonate salts will be sufficient to bring the wine into balance.
Malolatic fermentation will only remove malic acids.
However, in very cool areas where the grapes’ malic acid levels are very high, and there is also excess tartaric acid – the expense of double salts are often justified. The addition of this salt creates crystals will help remove both tartaric and malic acids.
Acidification – Increase acidity levels and reduce pH to remove the balance of the finished wine.
Acidification is universally practiced in all but the coolest parts of Southern Europe and may be used in moderate regions which experience a particularly warm or hot summer.
There are two ways to acidify a wine: by adding tartaric acid (this can be done before or after fermentation) or citric acid (which must be added after fermentation otherwise it creates acetic vinegar).
Some people prefer acid to be added before fermentation as they believe it integrates better into the finished wine. Wine acids generally are neutral in flavour and simply add to the structure and mouthfeel of the wine – apart from malic acid which tastes strongly of sharp green apple and acetic acid – which is reminiscent of vinegar.
Being able to acidify wine allows you the freedom to harvest later. Coonawarra for example is known for its big flavoursome red wines which are pretty high in alcohol (circa 14.5%), but they weren’t always this big and hearty. They used to harvest when the grapes were at optimum sugar ripeness and still had good acidity whereas now they will wait until the grapes have phenolic (flavour) ripeness and may well need to acidify afterwards, hence the rich concentrated flavours and high alcohol content from increased sugars.
Use of SO2 – Sulphur dioxide has been described by Jancis Robinson as the winemaker’s detol and can be used as an antiseptic, killing bacteria; an antioxidant – stops the oxidation of other molecules (by oxidising itself and therefore preventing oxygen from binding with anything else); and an antioxidasic – it helps to neutralise enyzemes that produce oxidation.
While Sulphur Dioxide has many benefits it needs to be applied carefully. However, too little and the wine is at risk of spoilage from bactera and unwanted yeast – they are aerobic and need oxygen to work and so sulphur dioxide inhibits their growth. The wine is also at a risk of oxidation and too little SO2 can result in a lack of freshness and the development of acetaldehyde (which create the flavour in fino sherry).
Equally, if too much SO2 is used the wine can develop unpleasant aromas of burnt matches and an unusually pale colour as SO2 can have a bleaching effect, in rose wines an unattractive orange tint can develop. Some asthmatics have adverse reactions to excess SO2, which is the same preservative found in fresh fruit salads and prepackaged sandwiches.
Oxygen – we’re always told oxygen is bad during winemaking and it is, as too exposure to oxygen can change the colour of a wine, making a white wine unnaturally deep, having a bleaching effect on red wines and giving all wines an unattractive brown tint. Excess oxygen can also remove freshness and create a wine that appears stale with flat, bitter aromas and which is of increased risk of bacterial spoilage.
But as I alluded to earlier, a certain amount of oxygen is during the wine making process is no bad thing. Too little oxygen and you’ll struggle to get fermentation started, yeasts need oxygen to work and without oxygen you’ll get a stuck fermentation. Oxygen can also help give complexity to a wine such as Chardonnay, and oak ageing will give very small levels of exposure to oxygen over an extended period.
So know we know about some of the additions that can be made in a winery, we were asked in class to make a series of winemaking decisions about how to create a cask-fermented Chardonnay.
So what style of wine are we tring to create with a cask-fermented Chardonnay? Well, not a cheap one, oak casks are not cheap and fermenting in cask is said to help better integrate the oak flavours so we can assume we’re creating a premium wine here. I’d expect a rich wine, with dairy/buttery notes from ageing on lees. I’d also look to achieve some oak influence and smoke, toast, vanilla and clove notes. My impression of a cask-fermentated Chardonnay is a wine rich with fruit and body where the oak is used to season the wine, not dominate it.
Our first decision is in the harvesting, do we want to press whole bunches of grapes or do we want individual grape? And if so, do we want to destem them before crushing and pressing?
Whole bunch pressing requires high capital costs as you need to have a very high press capacity because whole bunches take up more space than individual grapes. But it does result in a high quality juice, with low levels of particles and contains lots of peripheral pulp and the extraction is quick. So assuming money is no object we’ll whole bunch press with our cask-fermented Chardonnnay.
The next decision is how to clarify the juice? Options here are cold settling, centfriguation, diatomaceous earth filtration and floation.
Cold settling is the slowest but most effective and less invasive method of clarifiation and as time and money is not an issue, this is what we’ll do.
Next, we’ll add some yeast nutrients such as diammonium phosphate (DAP), thaimine or ammonium sulphate to ensure a healthy growth of yeast and avoid a stuck fermentation or the development of hydrogen sulphide. Highly clarified juice can cause yeast to produce hydrogen sulphide.
Talking of fermentation, we are going to ferment our Chardonnay in oak casks or 225l oak barriques to ensure good contact with oak (the smaller the barrel the greater the contact). Cask fermenation gives better integrated oak flavours and buffers the wine from harsh flavours.
In terms of age of barrel, a new oak barrel will give maximum oak extraction if the wine is strong enough to cope. We’ll use a mix of French and American oak and have a heavily toasted barrel to give the strong toast and clove characteristics.
In terms of yeast selection, this can be contentious territory. Uninnoculated yeasts can offer more complexity than uninnoculated ambient yeasts, but the results can be unpredictable and unreliable.
The majority of winemakers use innoculated yeasts as when they buy a specific yeast, they pretty much know how that yeast is going to behave. There are some that say this produces very ‘samey’ wines but with the choice of yeasts out there and number of different decisions that all impact on the final wine I’m not so sure.
One happy medium could be to use a starter culture, this requires using an ambient yeast from the winery and watching how the fermentation goes in one barrel and if it is going the way you want you can use this yeast to set off the rest of the barrels. If anything goes wrong only one barrel is lost, and a 225l one at that not a huge big vat, and we can use an innoculated yeast as our fallback option.
We want to ferment the wine at below 20 degrees C.
We will rack the wine off the gross lees (the big initial deposits of dead yeast cells that can leave a bitter taste) and leave in contact with the fine lees which will add texture. We will increase the influence of the lees by battonage or lees stirring this will add texture increasing body and improving mouthfeel, protect against excess oak by reducing astringency. Lees contact encourages the second, softening malolactic fermentation, because the lactic acid needed for malocatic fermentation feed on the micro-nutrients in the lees, and gives added complexity and the lovely buttery flavours we are trying to achieve.
We will then age in cask and in bottle, bottle aging will help create the honey, nutty characteristics we want.
I think we started with an oak-fermentated Chardonnay as at every stage in the winemaking process there is something extra a winemaker can do to improve the end result, there can be a lot of playing in the winery with this one. Next week, we’ll look at how to create a medium-dry Riesling, a classic Pauillac and a high volume red wine.
This year has been a weird one, full of new experiences- but one I wasn’t expecting and was thoroughly unprepared for was