CCO410 Wine Finishing

The globalisation of the wine industry has been a huge advantage for wine producers in New Zealand. Twenty years ago wine producers in New Zealand were rather isolated from the global market, and it wasn’t as popular to find international wines in our local supermarkets. This was common in the ‘New World’ wine producing countries. Although ‘Old World’ countries still dominate in terms of production, it has become far more accessible for smaller wine producing countries to export their wine, and also to ‘make a name for themselves’. ‘New world’ wine producing countries are also faster to adapt to changing trends in the wine-industry. In order for wine producers in New Zealand to be successful they need to “master the tastes of the global market” as consumption of wine in our local market is decreasing.

OIV ‘State of the World’ report

On the 22nd of April 2020 the OIV ( International Organisation of Vine and Wine) released their annual ‘State of the World’ wine sector report.

New Zealand

As of June 2020 and despite the challenges of the past 12 months, the New Zealand wine industry recorded its 25th consecutive year of export growth

(NZ Wine, n.d.)

Summary of New Zealand Wine

• There has not been any dramatic shifts (increasing or decreasing) from 2019 to 2020 in any of the statistical data.
• The producing area has increased by 5,435 hectares from 2011-2020.
• Both export values and export volumes have been steadily increasing since 2011
• It can be noted that consumption and domestic sales of NZ wine is trending down-wards, this could be due to the emergence of craft beers, and other trendy alcoholic beverages competing with the wine market.

Copper/Cadmium Test

The aim of this trial was to determine what type of reductive compounds are causing a wine to have a reductive wine fault or character. The wines were assessed by aroma only.

The reagents used were:

1. 1% w/v Copper (II) Sulphate solution
2. 1% w/v Cadmium (II) Sulphate solution
3. 10% w/v Ascorbic acid

The method was carried out as per laboratory manual. The aroma was compared, and the table below was used to interpret our results.

Results

Wine 1:

I did not pick up on the presence of an offensive odour in the control wine, I also did not notice a change in the aroma between the different treatments. It was revealed that the reductive compound was Dimethyl sulphide (DMS). As a fault DMS is described as having a ‘vegy’, ‘asparagus’ or ‘cooked corn’ aroma. The treatments used do not have an effect on DMS (as seen in table 1), therefore it makes sense that the aroma did not change.

In completing this trial it emphasises the need to have winemakers who are able to recognise faults even when present in small amounts. Although I did not pick up on the fault in the control wine, some consumers may detect the fault and this will discourage them from purchasing their wine.

Wine 2:

The cooked cabbage aroma identified in the control wine is characteristic of both mercaptans and disulphides. The addition of copper in glass 2, and the addition of ascorbic acid + copper in glass 4 removed the reductive wine fault. Disulphides cannot be removed through the addition of copper alone, therefore we can deduce that the reductive wine fault in this trial was mercaptans.

Wine 3

The rotten egg aroma identified in the control wine is characteristic of H2S, it is also characteristic that the Copper addition in glass 2, and the Cadmium addition in glass 3 would remove the H2S fault. Although the addition of ascorbic acid + copper removed the rotten egg aroma, a new fault was detected. Glass 4 had a noticeable sweet aroma, and we were informed that the addition of ascorbic acid could have oxidised the acetaldehyde in the wine. This sweet aroma was not observed by some of my other classmates, therefore it could have been a result of unintentionally adding a larger volume of ascorbic acid.

Why carry out this test?

The principle of this test is that different reductive wine characters react with different fining agents, including copper and cadmium salts. Depending on which fining agent removes the undesirable aroma the type of reductive fault can be identified. In a winery setting this trial would be carried out to determine whether any reductive sulphur compounds are present in the wine, and consequently specific measures would be taken to remove the fault in the wine.

H2S, Mercaptans, and Di-sulphide

Before discussing these volatile sulphur compounds we must first become familiar with the term ‘reduction’. The chemical explanation of reduction refers to the gain of electrons, and oxidation is the loss of electrons.

You have probably heard the word ‘reduction’ as a negative aromatic quality or described as a wine fault.  When a wine is described as being ‘reduced’ it usually means it has above-threshold levels of volatile sulfur compounds. But not all reduction is bad, and reductive wine-making is not the same as reduction….

Positive reduction aromas

As described in my last blog-post, the production of volatile sulphur compounds (or ‘thiols’) such as 4MMP, 3MH, and 3MHA have a desirable effect of the aroma of a wine. Other volatile sulphur compounds that produce ‘flinty’ aromas can also be desirable at low levels.

Reductive vs oxidative wine-making

Reductive wine-making simply refers to wine-making in the absence of oxygen. For example, Sauvignon blanc is typically fermented in steel tanks, protected with CO2 and kept in cool temperatures.

Oxidative wine-making refers to wine-making in the presence of oxygen. For example, Chardonnay typically undergoes secondary fermentation in barrel, allowing micro-oxygenation.

H2S- Hydrogen Sulfide

H2S is formed during fermentation, and is often described as having the distinct smell of rotten eggs.

The formation H2S is mainly due to the following:

• Alcoholic fermentation– yeast produce H2S when they use one of the sulfur-containing amino acids as a nitrogen source. If a ferment is stressed there is more likelihood of H2S formation.
• Elemental sulphur– applied to the vineyard to control powdery mildew, if there are residues of elemental sulphur in the ferment it can cause yeast to convert S (elemental sulphur) into H2S.

During fermentation H2S can be removed by liberating the H2S through sparging with oxygen. Application of nutrients, such as DAP, can reduce H2S formation. H2S has a low sensory threshold, meaning that if H2S is not controlled during fermentation it will mask other aromas in the wine.

Mercaptans & Disulfides

As talked about in my previous blog-post, H2S plays a role in the formation of other volatile sulphur compounds.

A reaction between H2S and other compounds in the wine can result in the formation of mercaptans. Mercaptans cause aromas such as ‘cooked cabbage’, ‘burnt rubber’ and ‘onion’.

Mercaptans are also undesirable as they can rapidly oxidise into disulfides. These disulfides result in more undesirable aromas in wine (see image).

Mercaptans can be removed from wine through the application of copper sulphate. A process in which copper sulphate reacts to form copper sulphide, which is highly insoluble and odour less.

Disulfides however, do not respond to copper sulphate. The removal of disulfides requires first reducing it to it’s mercaptan form through time-consuming methods such as applications of ascorbic acid and SO2, once reduced to mercaptan form it can then be treated with copper sulphate.

Due to the difficulties of removing these volatile sulphur compounds at their mercaptan and disulfide forms, it becomes clear how important it is to either prevent or treat H2S during fermentation.

References:

Goode, J. (2007). Mercaptans and other volatile sulfur compounds in wine. Wineanorak. https://www.wineanorak.com/mercaptansinwine.htm

Volatile Sulphides: Detection and Prevention. (2015). ETS Labs. https://www.etslabs.com/library/31#:~:text=Volatile%20sulfur%20compounds%20can%20contribute,effective%20treatment%20and%20prevention%20plan.

Thiols

Having worked in the wine-industry in Marlborough you’ve probably heard the word ‘thiol’ been talked about by every wine-maker and his dog. But what is a thiol? And why is it so important in making that typical Marlborough Sauvignon blanc?

Chemically speaking, thiols (also called mercaptans) are a class of organic chemical compounds.

This image shows the basic chemical composition of a thiol group. A ‘thiol’ group means a sulphur atom bound to a hydrogen atom. In comparison to alcohol and phenol groups where a hydrogen atom is bound to an oxygen atom.

So why does it matter?

It just so happens that volatile thiol compounds tend to be very aromatic!

Specific volatile thiol groups are also referred to as ‘varietal thiol compounds’. These varietal thiol compounds have a positive influence on the aroma of the wine. Some of these varietal thiol compounds include:

*OAV meaning odour threshold

Blackcurrant, passionfruit, grapefruit… these tropical aromas are very characteristic of Marlborough Sauvignon blanc, so you would be correct in concluding that Marlborough Sauvignon blanc has higher levels of varietal thiol compounds.

These ‘varietal thiol compounds’ are not present in the grape juice, they are instead present as precursors and are in a non-aromatic form. It is not until the grape juice is fermented that these thiol compounds transform into the volatile thiols, thus revealing their aromatic potential. Even then, not all of these ‘precursors’ become the volatile thiols.

Many studies have been undertaken to determine how to encourage the production of varietal thiol compounds, involving both wine-making and viticulture procedures. For example, the yeast strain plays an important role in the formation of volatile thiol compounds and specific yeasts strains can be purchased which claim to encourage the formation of more fruity thiols.

Not all thiols are desirable

The wine-world jargon can be cause for some confusion. ‘Thiol’ and ‘Mercaptan’ both refer to the class of organic chemical compounds where a sulphur atom is bound to a hydrogen atom. However, thiol usually refers to desirable tropical aromas, wheras mercaptan usually refers to negative vegetal aromas (see image).

It is not fully understood what causes these mercaptans, however it is believed that it is formed during fermentation, involving a reaction between H2S (Hydrogen sulfide) and ethanol/methanol.

Stay tuned…More on this in my next blog-post

References:

Goode, J. (2007). Mercaptans and other volatile sulfur compounds in wine. Wineanorak. https://www.wineanorak.com/mercaptansinwine.htm

Thiols and beyond. (n.d.). Wineanorak. Retrieved December 15, 2020, from https://www.wineanorak.com/thiolsandbeyond.htm

Volatile Sulphides: Detection and Prevention. (2015). ETS Labs. https://www.etslabs.com/library/31#:~:text=Volatile%20sulfur%20compounds%20can%20contribute,effective%20treatment%20and%20prevention%20plan.

Wineworks is a third-party bottling facility offering bottling infrastructure for New Zealand wineries. They have plants in Marlborough, Auckland and Hawkes Bay. Wineworks takes care of the bottling, storage and packaging using world-class technology and facilities. The bottling line and packaging system is mostly automated.

How the bottling process works

During our visit to Wineworks we first sat down and were shown a presentation where we learnt all about what is involved in the process of working at a bottling facility.

Raw Materials: Bottles

Wineworks will provide the winery with the packaging needed for the bottling process.

There are many different kinds of bottles that a winery can choose from, usually the type of bottle will depend on the variety that is being bottled. For example, Chardonnay and Pinot Noir are typically bottled in a ‘Burgundy’ bottle. (see image)

The shade of the bottle is also chosen by the winery. In New Zealand the ‘antique green’ shade is most popular.  Other shades include ‘flint’, and ‘champagne green’.

Wine bottles also come in an assortment of sizes. In New Zealand this will typically range from 375mL (demi) – 1.5L (magnum)

Raw Materials: Closures

The closures are also chosen by the winery. This is typically a screw-cap, but Wineworks can also supply the winery with corks, or LUX caps.  Less commonly used are zorks or vinolok closures

Collecting Wine

Wineworks uses tankers and isometric tanks to collect the wine from the winery. For nearby wineries they also have lines build in underground so the wine can be sent directly to wine-works. Once it arrives at Wineworks it undergoes laboratory analysis and this analysis is sent to the appropriate wine-making and logistics team- when ‘green-tagged’ the bottling process begins.

Bottling

After this presentation we had a tour of the bottling facility, where we all marvelled at the high-tech bottling facilities… just another day at the office for those who work there.

Wineworks has 9 bottling lines (between all plants). The bottling process is mostly automated, with advanced technology and facilities. (see image)

Prior to bottling the wine passes through a 0.45 micron membrane filter ensuring no bacteria or micro-organisms will pass through into the bottled wine. In order for the wine to pass through these membrane wine must be pre-filtered, either using cross-flow or other filtration methods. The wine must have a Filterability Index (F.I) of less than 1.2. If the wine does not pass the F.I the winery will have to pay a fee, or the wine will be sent back to the winery to be re-filtered.

The specified bottles will be de-palitized, rinsed and dried. The bottles are filled and the specified closures will be fastened onto the wine bottles. The outside of the bottle is then washed and dried ready for the labelling process. Once labelled the bottles will be packed into cases with dividers, palletized, stickered, and packed into storage.

References

Wineworks (n.d.) Wine bottling and packaging Wineworks. Powerpoint [Slides]. NMIT Moodle. 

Jackson, G. (n.d.). Types of Bottles for Wine – Bottle Shapes, Bottle Sizes and Other Options. The Beverage People. Retrieved December 14, 2020, from https://www.thebeveragepeople.com/how-to/wine/types-of-bottles-for-wine.html

Indevin is a contract wine-making facility, meaning that they produce wine for the retailer’s own label supply or exclusive brands. They are partnered with brands such as Gallo (USA), Waitrose (UK) and Tesco (UK). For example, they produce a Marlborough Sauvignon blanc for ‘Tesco Finest’, ‘Cowrie Bay’ for Waitrose UK, and ‘TeHua Valley’ for Wineworld Norway. 

Indevin exports their wine using flexi-containers (see image below), this involves filling a flexi-bladder (made up of multiple layers of Polyethylene) which is installed into a container.

 At Indevin, these flexi-bladders will hold 24,000L of wine. Specific containers are used, called ‘flexi-grade containers’, in order to be deemed ‘flexi-grade’ the surface of the container has to be smooth, without any bulges or sharp points. Any uneven surface could potentially puncture the flexi bladder inside the container. The containers are a standard 6.25m and have a valve at bottom for filling.

The process:

• A flexi-grade container will be dropped off to Indevin.
• At Indevin they have 7 spaces for these containers in their main dispatch pad.
• The Flexi-bladders hold 24,000 L of wine, it takes approximately 1 hour to fill 1 Flexi-Bladder.
• The Flexi-containers are held up on bison weights. Once 24,000L has flowed into the flexi-bladder the flowmeter will automatically switch off. To ensure the appropriate amount has gone into flexi-bladder it will be double checked using the bison weights and taking a dip.
• Indevin dispatch on average 35-40 flexi-containers per week
• All of Indevin Wine is Cold/Heat Stabilised, Cross-Flow Filtered, and Sterile Membrane Filtered prior to bulk dispatch. This ensures the wine will stay stable through it’s export journey (as Flexi containers are not temperature controlled), and prevent any spoilage due to bacteria/microorganisms.
• The wine is tested in the lab using a PCR (Polyamerase Chain Reaction) machine to ensure there are no yeasts and other potential microorganisms are in the wine that could cause spoilage during the export process.
• In the main dispatch pad there are the Membrane Filtration Systems, these filters will filter the wine down to 0.45 micron- also known as Sterile Membrane Filtration, ensuring that all bacteria or microorganisms commonly seen in wine will be removed- preventing the risk of spoilage during the export process. The wine is membrane filtered just prior to the filling of the flexi-bladder.
• Indevin keep retention samples.
• Indevin will organise the distribution, and through various contacts using different  inco-terms. This could be X-winery, FOB (Free on board), DAP (Delivered at Place)

Advantages: 

• Exporting through bulk dispatch results in less temperature variation of wine during export due to the larger volume. 

• Bulk dispatching wine extends the wine’s shelf-life as once wine is bottled it starts to deteriorate. The bulk dispatch delays the bottling process, Indevin primarily exports Sauvignon blanc which is not made for bottle aging or maturing.

• Cost Effective: Container holds 10,584 litres of bottled wine, compared to 24,000 litres of wine in a flexi, thus reducing the cost of transportation.

• Environmentally Friendly: In comparison to bottled wine a flexi-tank has a reduced weight and increased amount of wine thus reduces the carbon footprint