CCO410 Wine Finishing

“A geographical indication (GI) is a name, usually a regional name, that’s used to identify the origin of goods where some quality, reputation or other characteristic of the goods is related in some essential way to their geographical origin.”

(New Zealand International Property Office, n.d.)

In New Zealand we have legislation that regulates whether a wine company can state a specific region on a wine label. The current version of the Geographical Indications (GI) Registration Amendment Bill was passed by New Zealand’s parliament in November 2016.

The image below shows the Geographical Indicators currently registered in New Zealand.

In order to use one of the registered GI’s the 85% rule applies. If a wine label states ‘Marlborough Sauvignon Blanc’ at least 85% of the Sauvignon Blanc grapes must have come from Marlborough. 

On the global stage there is a certain reputation that comes with having a Marlborough Sauvignon Blanc, it is described as having a certain intensity with a multitude of herbaceous and fruity flavours/aromas.  Having registered GI’s was an important step for the New Zealand wine industry. The GI Act means there are more safe-guards in place to ensure a wine labelled ‘Marlborough Sauvignon Blanc’ is characteristic of our region, and the consumer is now aware of a certain quality which comes with having a Marlborough Sauvignon Blanc.  

Appellation Marlborough

Some companies believed the GI Act did not go far enough, and as a result ‘Appellation Marlborough’ was born.

 A wine can be certified by Appellation Marlborough if it follows these specific guidelines: 

ORIGIN – Wines are made from grapes that are 100% sourced from Marlborough vineyards. 

INTEGRITY – Wines must be made from grapes cropped at or below set parameters, established according to soil type and vine density variability. If a proposed wine contains any portion exceeding that level, it must be approved by an independent panel of qualified, experienced local producers.

AUTHENTICITY – Wines must be bottled in New Zealand.

SUSTAINABILITY – Associated vineyards are certified by a recognised sustainable viticulture scheme. 

(Appellation Marlborough Wine, n.d.)

If a company is registered with Appellation Marlborough and follows these guidelines they can present a Appellation Marlborough Wine certified quality mark (see image below). 

Do we need more registered GI’s?

Would this help or harm wine producers?

Many consumers buy a Central Otago Pinot Noir as they expect a certain quality from that region. Bannockburn is a sub-region of Central Otago and is one of the warmest and driest parts of the region, because of it’s climate and soil diversity the Pinot Noir produced in this sub-region has different characteristics than other areas of Central Otago. These qualities make a good case for Bannockburn becoming its own Geographical Indicator.

However, a label cannot state more than one geographical indicator. If Bannockburn were to become a Geographical Indicator it could not include Central Otago on the label.

On a global stage, who has heard of Bannockburn?

A consumer who regularly enjoys a Central Otago Pinot Noir may not know that some of that added complexity is due to the grapes that come from Bannockburn. If Bannockburn becomes a GI it could be detrimental to their sales, as it is no longer apart of the Central Otago consumer market- unless that consumer is educated in New Zealand sub-regions.

The wine aisle at your local supermarket has dozens, if not hundreds, of options for you to choose from. Once you make your decision and head to the check-out, why that wine? The label conveys a lot of information which helps us make our decision. Was it the vintage, variety, producer, or alcoholic content? Perhaps the label just caught your eye. 

In the wine industry there exists legislation which determines how you can label a wine, and this legislation differs depending on the country.  If a company wants to sell their wine in New Zealand they must comply with the New Zealand regulations, and if New Zealand producers wish to export, they must comply with that country’s legislation. 

Wine sold in New Zealand follows the labeling laws outlined in the Wine Act 2003 and the Food Standards Australia New Zealand code. The legislation requires that some information must be included on a bottle of wine. This is called ‘mandatory information’. 

The mandatory information in New Zealand includes: 

You will notice that it is not mandatory to include the variety or vintage on the wine label, a company can simply state ‘wine’, ‘white wine’ or ‘red wine’ under the ‘product name’. There are further regulations that determine whether you can state the variety or vintage, therefore it is optional. The legislation states that at least 85% of the fruit must have come from the stated variety or vintage in order to include this information on the label.

This regulation also applies to region, also known as ‘Geographical Indicator’. If a company wishes to state the region, 85% of the fruit must come from the stated region. 

If you pick up a cask of ‘Country White Wine’, it probably does not meet the regulations to state variety. 

Other optional information in New Zealand includes:

• Environmental, sustainability and organic claims
• Nutrition content
• Nutrition content claims
• Lower alcohol claims

If a company makes these claims on a label, they must follow strict guidelines.

Wine companies are also encouraged to display a health advisory information/Pregnancy labelling, and also a ‘Cheers’ logo (a website providing the consumer with information on safe drinking practices) but these are not mandatory.

Most New Zealand wine is exported, therefore a wine-company must go through a rigorous process to ensure their labels not only meet the labelling legislation for their local market but also meet the regulations for the country they are exporting to.

What is DCO2?

Carbon Dioxide is a colourless gas composed of one carbon atom and two oxygen atoms. When water is present CO2 will dissolve into the liquid (producing dissolved CO2) and a reaction will occur leading to the production of carbonic acid. Carbonic acid is a very weak acid but it contributes to why wines with more CO2 “give a hint of tartness”.    

Fermentation

We have all probably experienced the feeling of being punched in the face by carbon dioxide during harvest. This is because carbon dioxide is a by-product of fermentation, in a process in which -put simply- yeast converts sugar into ethanol and carbon dioxide.

During fermentation the wines become saturated with CO2, however post-fermentation the CO2 reduces due to processes such as rackings and cold stabilization. The amount of CO2 lost post-fermentation depends on its solubility. 

• Solubility: Solubility is a property referring to the ability for a given substance, the solute, to dissolve in a solvent.

 Factors that will impact the CO2’s solubility (or the amount lost) include temperature and alcohol content.  For example, warming will reduce the CO2’s solubility and therefore result in a reduced level of CO2. 

Post-Fermentation

Not only is Carbon Dioxide produced during alcoholic fermentation it is also an essential aspect of the finishing stages of the wine-making process. Carbon dioxide is sometimes introduced to wine, or reduced to desired levels depending on the style of wine. If a Sauvignon Blanc has too little gas it can be perceived as “lacking freshness”, and too much gas can make it uncharacteristically “spritzy”.

Measuring Instruments

In the finishing stages of the winemaking process it becomes important to have instruments to measure the amount of CO2 in a wine so it can be adjusted to desired levels. 

One instrument for measuring dissolved CO2 is the “Carbodoseur”, it is readily used as it is an easy test and relatively cheap. However, it is not always accurate as there are a lot of factors which could give false readings.

Using the Carbodoseur involves the following steps:

1. Take temperature of wine sample.
2. Fill the cylinder with sample holding Carbodoseur at an angle (fill until meniscus is at 100mL).
3. Fasten lid firmly.
4. Hold finger over central tube and shake vigorously.
5. Remove finger from centre tube to allow wine to escape.
6. Repeat process of shaking then removing finger until no more wine escapes from central tube.
7. Remove lid and measure the volume remaining in the cylinder.
8. Use the supplied table (taking the final cylinder measurement, and temperature) to determine the DCO2.

References:

Measuring dissolved CO2 in the winery. (2016, August). Vintessential.Com.Au. https://www.vintessential.com.au/tip-measuring-dissolved-co2-in-the-winery/

McDonald, C., & Baguley, R. (2015, August). ​Appliance Science: The compressed chemistry of carbonation. https://www.cnet.com/news/appliance-science-the-compressed-chemistry-of-carbonation/

B.W. Zoecklein. (n.d) GASES: CARBON DIOXIDE, ARGON, AND NITROGEN. https://www.apps.fst.vt.edu/extension/enology/downloads/wm_issues/Winery%20Gases/Winery%20Gases1.pdf

Lyrebird_cycles. (December, 2017). Measuring CO2. [Photograph]. Aussie Home Brewer. https://aussiehomebrewer.com/threads/measuring-co2.97298/

Dissolved Oxygen is the concentration of oxygen molecules in a liquid  

Oxygen is essential during the primary stages of alcoholic fermentation as the yeast need oxygen to thrive. If there is a lack of oxygen at these initial stages of fermentation it can result in sluggish ferments. If the yeast becomes sluggish and therefore stressed, they can produce undesirable by-products such as Hydrogen Sulfide.  

Exposure to oxygen during fermentation becomes even more essential when it comes to red winemaking. Red wines have a higher concentration of phenolic compounds which makes them more resistant to oxygen. The application of oxygen in red wines in the form of pump-overs and punch-downs can help elongate tannins and stabilize colour.  

Oxygen can also have a negative impact on the wine, specifically in the form of enzymatic oxidation, chemical oxidation and microbial oxidation.

Enzymatic oxidation– Enzymatic oxidation is during fermentation 

The major enzyme that causes browning in juice and wine is called PPO, this enzyme is what turns an apple brown after taking a bite. The PPO enzyme oxidizes certain phenolic compounds in the juice which results in the formation of quinone. Quinone results in browning, and can degrade the quality of a wine. The addition of an antioxidant such as SO2 to must can help prevent this browning caused by quinone.  

Another enzyme responsible for browning in wine is laccase, this is a result of fruit being harvested when botrytis is present. Laccase is particularly tricky for winemakers as it can continue to be active post-fermentation causing further browning and premature aging- application of SO2 will prove ineffective. 

Chemical Oxidation– Post fermentation

A chemical reaction can occur involving phenol, this results in the compound hydrogen peroxide being produced. The hydrogen peroxide produced can react with ethanol and produce acetaldehyde. This oxidation can cause premature aging such as  browning, loss of fruity aroma, and formation of a bruised apple, nutty aroma

Microbial Oxidation

Many of the major wine faults occur because of microbial oxidation as a result of bacterial metabolism during winemaking. These include acetic acid, acetaldehyde and ethyl acetate. Maintaining hygiene practices and addition of SO2 can help prevent microbial spoilage in wines. 

How can we prevent this?

In learning of the negative effects of oxidation it demonstrates how important it is to reduce oxygen pick-up during the winemaking process.  Ensuring a winery has proper procedures in place is of the utmost importance. Some of these procedures include: gassing lines/tanks, replacing any damaged seals, minimizing headspace in tanks, and maintaining sufficient SO2 levels. 

Having accurate measuring instruments in place is also important so action can be taken if dissolved oxygen levels are high. 

References:

A Simplified View of Chemical Oxidation Mechanisms in Red Wines and the Role of Sulfur Dioxide. (2016, June 20). Techniquesinhomewinemaking.Com. https://www.techniquesinhomewinemaking.com/blog/a-simplified-view-of-chemical-oxidation-mechanisms-in-red-wines-and-the-role-of-sulfur-dioxide/

TECLEMARIAM, T. (2019). What is Oxidation Doing to my Wine? Winemag.Com. https://www.winemag.com/2019/04/09/wine-oxidation/