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New World Wine Maker Blog - Technical Articles

Sensory evaluation of mouthfeel in wine

by Renée Crous, Valeria Panzeri & Hélène Nieuwoudt

Sensory panels often avoid the evaluation of mouthfeel sensations in wine, since it implies (for many non-wine experts) complex, and abstract concepts. However, mouthfeel is an important dimension of wine quality, and it is, therefore, necessary that these properties are also included in routinely sensory tests. In our recently completed Winetech funded research project IWBT W13/02, “Rapid descriptive sensory methods for wine evaluation – special focus on further optimisation of rapid methods and streamlining of workflow”, we have developed two useful protocols for the assessment of mouthfeel in wine that can be used by sensory panels in the industry and research. This article describes the protocol that is based on the classic descriptive analysis (DA) method. In line with the objectives of project IWBT W13/02, we also optimised a rapid sensory method, polarised sensory positioning (PSP) to evaluate mouthfeel in wine. The rapid method does not require a trained DA panel and can be completed in shorter sessions. The protocol for the rapid method is discussed in a subsequent article.

What is meant by mouthfeel?

Mouthfeel refers to the sensory perceptions experienced in the mouth when a wine is consumed. Wine judges often describe wine as “full and round with good concentration, and length”, thereby implying that the product has good mouthfeel properties. While these phrases are commonly used in the popular media, people differ in their understanding of what exactly is meant by them. In scientific publications, several terms are grouped under so-called in-mouth sensations; these include fullness, heat, complexity, balance, length and mouthfeel.

Evaluation of mouthfeel by sensory panels

It is a challenging task to train a sensory panel to evaluate wine mouthfeel sensations. DA is one of our most accurate sensory test methods and provides two important outputs. Firstly, all the sensory properties that are perceived in a set of wines are identified and named by a panel of trained tasters. Secondly, panellists also score the intensity of each property on a line scale (ranging from 0 to 100, for example).

Physical standards are used to train a panel for the first task (identification of sensory properties). For example, a fresh lemon can serve as a standard for the lemon character in wine aroma. It is clear that all the panellists must have agreement on the sensations of the lemon character, as well as the particular word that describes the specific character, before the panel can proceed to assess the wines. With abstract concepts, such as length, complexity, and balance, there are no so-called physical standards, and an alternative plan must be made during training of the panel.

Another major challenge is to calibrate panellists to rate the intensities of the mouthfeel sensations on a line scale. It speaks for itself that the line scale must be used consistently by different panellists and on independent sets of wines; otherwise, comparative studies are not possible.

To illustrate these challenges: in this Winetech project, we wanted to evaluate the mouthfeel sensations of old-vine Chenin blanc wines (produced from vines 40 years and older) with the DA method. It is well known among wine experts that the old-vine Chenins have much more complex mouthfeel properties, compared to some younger vine Chenins. For panellists to use the line scale consistently to showcase these differences, they need to have in-depth experience and knowledge of the entire product category. This is seldom the case. Also in dealing with this challenge, adjustments had to be made to the standard DA protocol …



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Catch a whiff…

The total acidity in wine consists of two main components; non-volatile acid (including malic acid and tartaric acid) and volatile acid (VA). Volatile acid comprises of a group of volatile, organic, steam distillable acids. Concentrations mostly vary between 500 to 1000 mg/L, with almost 90% of volatile acidity consisting of acetic acid. The rest is mostly propionic- and hexanoic acid, as well as other fatty acids from yeast and bacterial metabolism, as well as ethyl acetate.

The most common VA concentrations in wine are around 0.4 g/L, with a legal limit of 1.2 g/L (see Table 1 for legal limits). The sensory threshold value in red wine is approximately 0.6 -0.9 g/L. whereas low, almost unnoticeable levels add to aroma complexity. With regards to the sensory attributes of VA; it contributes to the taste intensity of non-volatile acids and tannins, while the perception of VA itself is masked by high concentrations of sugars and alcohol. Acetic acid smells of vinegar, while ethyl acetate smells more like bruised apple and Cutex remover.

Volatile acidity production takes place mainly due to the oxidation of ethanol or the metabolism of acids/sugars. Ethanol is the primary energy source for acetic acid bacteria (AAB). Acetic acid bacteria are microscopic, single-cell organisms with enzymes included in their cell walls. The most common AAB present in wine include Acetobacter aceti, Acetobacter pasteurianus and Gluconobacter oxydans. These organisms are aerobic and need oxygen for survival. Acetic acid bacteria have the ability to oxidise alcohol to acetic acid, which in turn will, via esterification with ethanol, be converted to ethyl acetate. Ethyl acetate possesses a lower sensory threshold value compared to acetic acid and both acetic acid and acetaldehyde (a by-product of ethanol oxidation), are toxic to Saccharomyces cerevisiae and can contribute to sluggish- or stuck fermentations.


Origin and mechanism of oxidation…

During fermentation, the possibility of VA production is increased through the following practices: high risk must, risky winemaking practices and poor management of cellar conditions. Sources of VA after fermentation include cellar practices with specific focus on barrels: the amount of headspace, barrel age, oxidation and sanitary state of the barrels. Most AAB infections will take place in the cellar itself; mainly due to low acids and sulphur dioxide levels, together with oxygen exposure.

There are various sources that can add to the VA concentration in wine; the most conspicuous being:

  1. wild yeast e.g. Brettanomyces, Kloeckera etc. and as a natural by-product of S. cerevisiae

    Acetic acid is produced as an intermediary product of the pyruvate dehydrogenase metabolic pathway. This metabolic pathway is necessary and responsible for the conversion of pyruvate to acetyl-CoA. Last mentioned is imperative for anaerobic processes like lipid biosynthesis. This reaction is catalysed by alcohol dehydrogenase, whereby acetic acid is formed via the oxidation of acetaldehyde (produced from pyruvate during fermentation).

  2. lactic acid bacteria (LAB) during fermentation

    Heterofermentative LAB possess the ability to metabolise glucose (residual sugar), via the phosphoketolase metabolic pathway, and convert it to CO2, ethanol, acetic acid and lactic acid during malolactic fermentation. The first step in the citric acid metabolism produces acetic acid via citrate lyase activity, during which the conversion of citric acid to oxaloacetate, produces acetic acid.

  3. acetic acid bacteria

    Membrane-bound alcohol dehydrogenase oxidises ethanol to acetaldehyde. This intermediary is then oxidised further to acetic acid via membrane-bound aldehyde dehydrogenase.

  4. non-microbial source

    The chemical hydrolysis of wood hemicellulose, as well as the oxidation of gape phenolic compounds can result in the production of VA.

Factors that influence VA production…

  1. Sugar/osmotic pressure. Higher sugar concentrations result in a longer lag phase, which in turn lead to lower viability and growth potential of the yeast cells. Higher sugar concentrations together with low nitrogen levels lead to increased acetic acid concentrations.
  2. Fermentation temperature. Higher temperatures lead to higher VA concentrations.
  3. Yeast strain selection. The ability to produce VA id dependant on the specific yeast strain.
  4. The production of acetate esters e.g. ethyl acetate. This production is dependent on the yeast strain, the presence of indigenous yeast, fermentation temperature and SO2 concentrations.
  5. High initial acetic acid concentration. Rotten grapes, high sugar concentrations, pH and fermentation temperature at the start of fermentation will lead to increased acetic acid concentrations.
  6. A large bacterial population. High temperatures during storage of the wine (> 15°C), higher pH levels and lower alcohol and free SO2 concentrations, as well as poor cellar hygiene, will favour the survival of a bacterial population. 

Preventative measures…

  1. 1.     before fermentation:
  • monitor sugar and pH in the vineyard
  • do not mechanically harvest grapes that could be a potential risk
  • maintain sanitary conditions in the cellar e.g. equipment
  • use healthy grapes (avoid overripe)
  • do not excessively clarify the must, but a degree of clarification will reduce the indigenous microbial population


  1. 2.     during fermentation:
  • do acid adjustments if necessary to maintain low pH
  • maintain protective SO2 concentrations
  • use low VA-producing yeast strain
  • use sufficient nutrients during alcoholic fermentation
  • ensure fermentation is complete (no residual sugar / temperature fluctuations / re-inoculation)
  • reduce exposure to oxygen, but keep in mind that oxygen is necessary for alcoholic fermentation, as well as colour stabilising tannin reactions in red wine, so a degree of oxygen is required


  1. 3.     after fermentation:
  • inhibit malolactic fermentation with lysozyme if necessary
  • remove wine from yeast lees
  • adjust free SO2 levels to 40 ppm
  • ensure that wine is being stored in full containers
  • ensure sufficient sanitary state of barrels
  • correct usage of barrels
  • regular top up of barrels
  • bottling practices are important e.g. membrane filtration



As mentioned above, there are a variety of preventative measures, but all these techniques are irrelevant if a winemaker sits with a high final VA concentration in his wine. Correctional options include blends, reverse-osmosis and nano-filtration.


1. How to diffuse a volatile situation. Zoecklein et al. 2005.

2. The origins of acetic acid in wine. M. Lambrechts.

3. Volatile acidity in wine. R. Gawel.

4. Current vineyard and cellar events. Sources of volatile acid formation in wine and potential control measurements. C. Theron.

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Creating Hybrid Wines True to Style

Over the years, I’ve noticed that it’s easy for wineries to fall subject to – what I like to call – the “ice cream syndrome.” In this case, one varietal wine is made for each wine grape variety brought into the cellar. Soon, a wine list in a tasting room can feel a bit like a list of ice cream flavors on an ice cream shop menu:

  1. Chardonnay
  2. Grüner Veltliner
  3. La Crescent
  4. Cayuga
  5. Cayuga Reserve
  6. Moscato
  7. Pinot Noir
  8. Cabernet Sauvignon
  9. Cabernet Franc
  10. Cabernet Franc Reserve
  11. Chambourcin
  12. Noiret
  13. Chancellor
  14. Concord

The list can go on and on.

Listing the variety name on a wine label has its benefits. Many fruit wines, obviously, would benefit from a name that reflects the fruit the wine is made from. Additionally, American consumers tend to identify with many wine grape variety names on a wine bottle. This is especially true when names are well-known like Chardonnay, Cabernet Sauvignon, Moscato, etc.

However, what about French American Hybrid wine grape varieties? In some of my previous travels, I heard local grape growers and winery owners reject the integration of more hybrid wine grapes because they found them difficult to sell to consumers. There is lots of reasons that may contribute to this including …


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Oxygen management during winemaking

By Charl Theron of Wineland Media

The first spontaneous reaction of winemakers, when air or oxygen during winemaking is discussed or mentioned, is its negative association with the oxidation or browning of wines. The correct oxygen control can, however, have various advantages and contribute positively to wine characteristics.

An analysis of faulty wines at the well-known International Wine Challenge in London showed that oxidation or reduction are the two most important sources of faults, which occurred the most in wines. It is the extremes of oxygen exposure, either too much or too little. The controlled exposure to oxygen can, however, prevent both problems. The following six ways of controlled oxygen exposure exist during winemaking:

  1. Hyper oxygenation is the planned browning of juice prior to fermentation by means of a high oxygen addition of 8 to 30 mg/ℓ over a few hours, in order to remove potential browning components from the juice.
  2. Macro oxygenation is the dosing of 8 mg/ℓ oxygen halfway during fermentation to ensure a smooth and complete fermentation. It is often added together with nitrogen yeast nutrients.
  3. First phase of micro oxygenation (MOX): It is applied after fermentation, but before SO2-addition over a period of two to six weeks to stabilise colour, add more body to the wine and improve the longevity of the wine. It is a continuous dosing of oxygen at 1 to 5 mg/ℓ daily and depends on the oxygen appetite of the wine. This is 20 to 100 more than the oxygen supplied by barrels. The dosing units are either expressed as mg/ℓ/month (30 to 150) or mℓ/ℓ/month (20 to 100).
  4. Second phase of micro oxygenation (MOX): It is continuously applied after malolactic fermentation (MLF) and SO2-addition over a period of four to 12 weeks to refine the wine structure, integrate aromatic compounds like pyrazines and oak flavours, soften wood tannins and limit reductive tendencies. Dosages vary from 3 to 12 mg/ℓ/month or 2 to 8 mℓ/ℓ/month.
  5. Third phase of micro oxygenation (MOX): It is continuously introduced after barrel maturation when the wine is one or two years old over a period of two to 12 weeks to harmonise wood tannins and limit reductive flavours before bottling. Typical dosages are 0.4 to 3.0 mg/ℓ/month or 0.25 to 2.0 mℓ/ℓ/month.
  6. Ciqueage: It is named after the noise made by the solenoid, when the remote control is pressed to liberate oxygen. It is the punctual introduction of oxygen during maturation at 1 to 2 mg/ℓ, which is equivalent to the oxygen uptake during rackings.


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Putting the Theory Behind the “Vinotype” to the Test with Science

By Becca Yaemans of The Academic Wino

The concept of wine and food pairing is one that is well ingrained in many people’s minds: red wine with red meat, white wine with fish, etc.  The idea is that the complexities of a specific wine will complement best with the composition of a specific type of food. For example, as Master Sommelier Evan Goldstein suggests in his book Perfect pairings: A Master Sommelier’s Practical Advice for Partnering Wine with Food, Cabernet Sauvignon works very well with red meats as the body and big tannins require fat and protein to balance out and harmonize with the wine.

There is another, more recent approach out there, Vinotyping, that effectively throws out the whole idea of one perfect wine pairing with one perfect food type and instead focuses on the consumer themselves, which is led by Master of Wine Tim Hanni. A play on the word “phenotype”, the Vinotype approach focuses on an individual’s own genetics and experiences, and categorizes that individual as one of four different Vinotypic classifications: sweet, hypersensitive, sensitive, and tolerant.

Stepping back a little bit to take a quick glance at the science behind the Vinotype concept, it helps to have a basic understanding of “genotypes” and “phenotypes”.  In the most simplistic terms, your genotype is basically your genetic code.  You get half your genes from mom, and half from your dad, and the combination of the two for any given trait is your genotype.  Phenotype, on the other hand, is this genotype in “real life”.  In other words, it’s the observable characteristics that you see based upon your genotype and interactions with the environment.

For the Vinotype theory, it focuses the phenotype on how it relates to wine and wine preferences.  As Hanni defines in his book Why You Like the Wines You Like, the “vinotype” is “the set of observable characteristics of a wine-imbibing individual resulting from the interaction of its genotypic sensory sensitivies in a wine-related environment”.  So, in other words, your vinotype is a combination of your genetics and your experiences with wine and other beverages, and the interaction between the two.

Putting Vinotyping to the Scientific Test

In a new study published in the International Journal of Wine Business Research, researchers from Michigan State University aimed to evaluate the Vinotype theory from a scientific perspective, by looking at any association between everyday food and beverage preferences to wine preferences, as well as whether one could predict what kinds of wines someone would like based upon their everyday food and beverage choices.

The Study Approach

To answer these questions, participants first completed a questionnaire to determine their food and beverage consumption habits as well as their preference.

Next, participants were invited to a reception where they would taste 12 different food and wine combinations at different stations. At each station, participants were asked to taste the wine and food items separately and to rate them separately.  Then, they were to rate their how much they liked or disliked the combination of the two items.

For the food and wine pairing stations, the researchers recruited some of their students to identify combinations they believed would be either well liked or disliked by most people (which they determined via investigations and research).

The reception lasted about 2 hours, with the total amount of wine and food consumed per participant adding up to about 530mL of wine (44mL pour per station) and a full meal of food (appetizer sized portion per station). Participants approached each station in random order, depending upon how busy a particular station was at the time.


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CHINA: Yes? No? Maybe?

If you are a winemaker that is looking to expand your export market, you would have been living under a rock if the land of rice and tea and more recently wine, have not crossed your mind.

Since the economic reforms of the 1980’s, wine consumption in China has grown dramatically. Despite only having a per capita consumption (per person/per year) of 1.5L (compared to a whopping 50L of the delightfully intoxicated French), with a population that is fast approaching 1.4 billion, China is ranked as the 5th largest consumer of wine. Not to be outnumbered by their thirst for wine, China is also the 5th largest producer of wine in the world, seeing an average 60% increase in production every five years.


In terms of wine preference, red is pretty much leading the race, with white wine consumption trailing considerably. The colour red itself is of great significance, being associated with prosperity, happiness and celebrations (compared to white usually reserved for mourning and funerals). There is also a significant correlation between the tannins found in red wines and those found in the number one beverage in China, tea. As a very health conscious nation, the health benefits associated with red wine also play an important role.

Current consumption methods of wine is quite appalling to any Western wine drinker. You think adding ice to a glass of wine is a major faux pas…consider this…wine in China is consumed in a ‘shooter’ like fashion, with the whole glass being consumed in one go after a toast. White wines served with Coca-Cola and red wines with Sprite are also common sites. Wine by the glass is still very much reserved for upmarket restaurants only. At the moment, there are two main market segments. The top wine segment consisting of very expensive red wines that are very popular amongst the rich and famous. On the other end, the lower entry level market is growing in popularity and consists of more easy-drinking, lower quality, cheaper wines. As far as the division between bulk and packaged wines for export to China goes, the figures for 2006-2011 are displayed in Figure 1. Packaged wine exports saw an immense increase of 1206%, compared to the 74% decrease in bulk wine exports. This is an indication of the maturing tastes of the Chinese consumer.

In terms of distribution, your importer could distribute your wine via a couple of channels (Figure 2). Most popular would be ‘on trade’ (wine is sold and consumed on the same premises) and ‘off trade’ locations.

So, the biggest question remains: should you or should you not export to China? What follows below are three lists consisting of factors that make exporting to China a good idea, a bad idea or an ugly idea.

The heck to the NO list…

  1. French wine accounts for 50% of the wine imported into China. This is followed by countries such as Australia, Spain, Chile, Italy and the USA. South Africa will have to do considerable work to rank amongst these countries.
  2. The Chinese culture is well-known for their ability to copy…anything…and wine is no exception. Counterfeits of your wine is a very real threat to your brand and your reputation.
  3. Trademark squatters are individuals who register well-known foreign brands. Upon entering the country with your brand that have already been registered, you have some options (all of which will burn a considerable hole in your wallet): buy back your trademark, rebrand to create a new trademark or negotiate for the right to use your own trademark. Unfortunately, a ‘first to file, wins’ attitude exists in China, making this a challenge.
  4. It is still very expensive to export to China. Think 14% customs tariff, 17% VAT and 10% consumption tax. There are current trade agreements taking place between South Africa and China, but these are still very much under construction.
  5. China is enforcing a much stricter inspection policy. Wine arriving in China will now be scrutinised for three major parameters: alcohol, sugar and metal concentrations. Wines have to have an alcohol content of within 0.5% as printed on the label. The sugar content has to correlate with the type of wine your importer has registered your wine as (dry, sweet etc.) and thee main metal concentrations have to be within specification: copper (< 1 mg/L), manganese (<2 mg/L) and iron (<8 mg/L). If it is rejected on the basis of one of these analysis, the wine will either be destroyed or sent back at your expense, so test everything before it leaves the country.
  6. General challenges of exporting to China include a lack of transparency, unreliable information, the handful of giants that control the local wine industry, consumer and cultural differences, as well as the added logistical challenges of distribution.
  7. The local production could address the growing demand for wine. Take into consideration that the local workforce consists of over 80 million. The arable land covers more than 1.4 million kilometres. China is a country with a large number of modern business leaders, no shortage of technological knowledge and ability, as well as massive capital inputs.

The MAYBE this is a good idea list…

  1. Red wine consumption outnumbers that of white wine by 85% versus 15%, respectively. Because female wine consumption is on the increase, this ratio could shift in favour of white wines and present possible new target markets.
  2. Wine in China is very much a French affair. Wine is synonymous with France for most consumers. Changing this perception will be challenging.
  3. Trademark squatters is a real threat. Make sure legislation is on your side.
  4. The local Chinese wine production is still accounting for 80% of wine consumption in China.
  5. With the austerity program in place, lavish spending is being decreased.
  6. There will be a natural cooling down period in consumption. The growth percentage of 143.3% from 2008 to 2012 is predicted to decrease to a more moderate 33.8% from now till 2017. This is still a hefty number considering the population size.
  7. Growth will more likely happen in the middle and lower class wine sectors.
  8. Because the Chinese wine consumer is such a newbie to the world of wine, considerable education will be required.
  9. The increased volume and value of Chinese wine imports will also experience a natural cooling down period.

The YES, let’s do this list…

  1. China is a growing country, not just with regards to population size: the wine industry, per capita consumption and wine sales are all on the increase.
  2. Only one in every five bottles of wine consumed, is imported.
  3. The Chinese consumer is becoming more mature in their tastes and preferences. This means that they are spending more money and even moving into the sparkling, white and rosé wine sectors.
  4. The Chinese government has launched an austerity program in order to cut down on lavish spending (including those fancy, very expensive bottles of red wines served at banquets). This has forced importers and distributors in search for other markets to explore.
  5. The total worldwide wine consumption is growing and this future growth is going to be driven by Asian and American markets.
  6. Imports to China are still growing in volume and value.
  7. The most important role-player in the Chinese wine industry is THE CHINESE WINE CONSUMER. They are open and enthusiastic and with an ever-increasing love for the Western culture, including wine. The modern Chinese consumer is earning more money, buying more and willing to spend money on better quality goods. These consumers are becoming more aware of wine and the associated health benefits, especially compared to traditional and local high alcohol drinks. Because they are travelling abroad more often, they are experiencing wines in a more global manner and would like to be able to have similar experiences in their home country once they return. They are interested in the Western lifestyle and luxury and this is what wine represents; it is seen as a symbol of: an urban lifestyle, sophistication and social status.
  8. China is well-known for their so-called trademark squatters and counterfeited wines, but changes in Chinese legislation and government intervention have started addressing these issues.

So you have decided to export to China…now what?


The Chinese prefer smooth, medium-bodied red wines that are fruity and not too acidic. Popular cultivars include Cabernet Sauvignon and Merlot. In summer months, with the warmer weather, Chardonnay and Sauvignon blanc become more popular.


The modern Chinese wine consumer lives in the city and are young coming from wealthy families. Fifty percent of consumers are 25-44 years old and educated. They see wine as a product of culture and luxury and a sign of popularity and reputation. Wealthy female consumers are on the increase and they are more willing to pay for their favourite items. So if you can cater for the female tastes, you will grow your sales. The Chinese are a face saving nation. You have to make them feel comfortable with their (lack of) wine knowledge and their choice of wine. Use your packaging wisely to tell of the origin of the wine and as an indication of the price. Focus on the individual consumer and the younger generation.


Ideally, your Chinese importer and distributor should be China-based, preferably in one of the larger cities and specialise in wine distribution. You require a distributor with the necessary qualifications in order to import and sell wine. Trust is an important factor in order to successfully conduct business in China. these relationships take time to establish and ideally you should be introduced or recommended by a mutual acquaintance.  Your distributor should sell a good product for a specific market, have a good network in place and be dynamic. Keep in mind that your distributor will require assistance from both entities involved in the exporting and importing of your wine.

Some pointers…

  1. You will have to educate the importer and consumers about your country, your wine, your brand and your story.
  2. Present different wines in different price categories to avoid product conflict for your distributor.
  3. Visit China. Often. You will require hands-on, pro-active marketing on ground level.
  4. Make an effort to understand the cultural differences. To build dynamic, long-lasting business relationships require respect, patience, trust, communication and an idea of social etiquette.
  5. Make all your marketing material available in Chinese, including websites. Have lots of pictures and information on your history and family.
  6. To enter the market, stick to red wine, cork closures and classic French packaging.
  7. Keep in mind that we have some major selling points as a South African brand: two indigenous  cultivars, Chenin blanc and Pinotage, as well as the winelands as a major tourist destination. Think Brand South Africa. Some institutions that could help, include: The Department of Trade and Industry 9TDI), Trade and Investment South Africa (TISA), Department of Tourism, Wesgro and WOSA.
  8. Register your trademark and do an online search of registered trademarks in existence in the Chinese market.
  9. Analyse your wine before it leaves the country.
  10. Keep in mind that the Asian marker means more than just China, think Hong Kong, Vietnam etc.
  11. We have wines with big, bold aromas and flavours, perfect for going up against the spicy cuisine of the Chinese. Keep this in mind when planning promotional/marketing dinners and/or events.
  12. A handy website filled with people who have been there, done that and got the T-shirt:

These are only a number of factors to take into consideration when making the decision of whether to dip a toe in the Chinese wine market or to make a splash.

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