Course:FNH200/2012w Team23 Wine

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UBC's Take on Wine

Introduction

When one thinks of wine, one asks what grapes are chosen for each wine? What fermentation process does each wine go through? What does it mean when a wine has been aged? What are the regulations for wine labeling? Most importantly, why are fermented wines safe to consume?

Wine is consumed and appreciated by many around the world. Each batch of wine has its own unique characteristics, much like a fingerprint. Technology has allowed us to scientifically decipher the contents and chemical reactions that contribute to a wine's organoleptic features. In this analysis we shall examine the wine industry and offer consumers insight into what factors and methods lead to their desired product. We will provide an overview of what the key stages of wine processing are, and most importantly how winemakers ultimately develop unique and pleasing flavours for consumers. The standard procedures will be outlined, while also some of the regulations surrounding the Canadian wine industry shall be explored.


Red and White wine displayed

Red Wine Production

Harvesting & Preparation

Perfect grapes are essential for the production of a good red wine. There are many factors that contribute to growing grapes, such as region, climate, and variety. Upon ripening, grapes are harvested based on their maturity, sugar content, acidity and pH.[1]

Caption: This photo by WayneandWax shows grape must for red wine.


Under ripe grapes have a lower sugar content, which affects the flavor, color and acidity. Over ripe grapes tend to be rich in color, sugar and flavor, but low in acidity. Grapes are usually harvested with a sugar content rage of 22° to 24°Brix.[1] Growers can measure °Brix with a refactometer (MT700) or standard hydrometer (MT310).[2] If the sugar content is too low, sugar or sugar syrup can be added before the fermentation process. This process is called amelioration, and can increase the sugar content while decreases acid due to dilution; therefore, the amount added needs to be well considered. The acidity of the grapes should range 6.5 to 7.5g/L and pH should range 3.4 to 3.6 pH.[1] Depending on the wine being made, different grapes are harvested for use.


Caption: Making grape must by mechanical means.

After harvesting, the grapes are transported to a winemaking facility. A machine called the Stemmer or Crusher removes the stems and crushes the grapes to break open the skin.[1] This allows yeast to enter and begin fermentation.[2] The resulting product is called must, a mixture of grape juice, grape skins and seeds. Sulfur dioxide is then added to treat the must by killing any microbes, indigenous yeasts and harmful bacteria before fermentation. Depending on the wine, some winemakers will add a fraction of stems to the must to extract more tannin. Adding too much stems can result in a harsh flavour and loss of pigmentation.[1]

Maceration

The next step in the winemaking process is called maceration or cold soak. The must is kept to sit for a few days to extract more pigments and phenolic compounds from the skin to improve color, body and mouth feel. The must is kept in an atmosphere of 15°C to 20°C for a few days to slow the onset of any remaining indigenous yeast from fermentation.[1] Depending on the desired product, the must may not have the same desired level of acid, sugar and pH. Before proceeding to the addition of yeast and fermentation, the winemaker should perform any adjustments needed to the must.[2]


The selection of yeast for fermentation contributes largely to the quality, flavor and mouth feel of the final wine. Winemakers must take into consideration choosing a suitable strain of yeast to avoid unwanted byproducts such as acetic acid, ethyl acetate and hydrogen sulfide. This results in potent smells that resemble rotten eggs or nail-polish remover. Generally, commercially produced dry strains of active wine yeast are used. Indigenous yeast may also work but may not have the desired effect depending on the wine. Using commercially produced yeast can standardize the flavour and characteristics of wine products [1].


The skin of the grapes play a large role in the quality, taste and color of wine. During fermentation, tannin and pigments are the major constituents that are extracted from the skin. The purple-red color of the grape is a result of anthocyanin pigments within the outer layer of grape skin. The pigments exists in a color and colorless form that are influenced by pH and the presence of sulfur dioxide. By lowering the pH, winemakers can shift the equilibrium to favor the formation of more pigments in color form. Sulfur dioxide can also act as a bleaching agent to the pigments. Tannins are polymeric phenols that can react with pigments to form polymeric pigment complexes. These complexes are less acidic and sulfur dioxide sensitive, giving them the ability to stabilize wine color [1]. During fermentation, the yeast releases carbon dioxide and heat. The heat can further increase the fermentation rate and extraction of color and phenolic compounds. If the temperature rises above 32°C, the environment can promote the growth of undesirable organisms and off-odor compounds [1].


Alongside the heat, the released carbon dioxide can push skins and seeds up to the surface, creating a “cap”. Caps can trap heat that can result in an uneven fermentation and extraction. To manage the undesirable cap, winemakers will have to do perform “Punch down” or “Pumping over” a few times a day. A punch down is where a large piston will “punch” the cap down and pumping over is when the juice is drained from the bottom of the fermenter and redelivered to the top. The first method would favor an open stainless steel fermenter while the second would favor a closed-top fermenter. Larger wineries also tend to use autofermenters and rotary fermenters for a thorough mixing of the must. Managing the cap is important to redistribute heat and improve flavor extraction. After the first fermentation process, the juice will be drained while rest of the solids, called the pomace, will be sent to pressing for further extraction [1].

Alcoholic Fermentation

Alcoholic fermentation involves a complex anaerobic transformation of glucose and fructose from grape must to ethanol and carbon dioxide using the yeasts, S. cerevisiae and S. bayanus[3] Yeast cultures metabolize the sugars through the process of glycolysis which produces pyruvate as its final product. In turn, pyruvate can be converted into ethanal and carbon dioxide through the enzyme pyruvate decarboxylase and ethanol can be further reduced to ethanol[4]

Composite fermentation tanks

Natural and cultured yeast are two types of yeast involved in winemaking.[5] Natural yeasts exist on the sticky, waxy grape skin and cultured yeast is added by winemakers to produce a standard aroma.[5] Sulfur dioxide not only is added to the grape must to kill natural yeast cells but also is added to standardize wine flavors and aroma.[6] Sulfur dioxide can also inhibit browning enzymes that cause discolouration of the wine, reducing oxidation and bacteria growth.[6]

Temperature control is crucial to yeast growth as well as flavour and colour extraction from grape skins. It also allows the accumulation of desirable products such as ester bodies.[6] Ester bodies contribute to the wines' characteristic flavour. The ideal temperature for alcoholic fermentation is between 21-29.5 degrees Celsius. As the temperature and amount of immersed grape skins increase, more tannin will be produced. As a result, the wine will possess a more pigmented, fuller and richer taste.[5] A lower fermentation temperature will produce a more lighter, subtle aroma and can enhance the aromatic profile of the wine.[7] [5]

Wine-making equipement at Hanzell Vineyards A


Day one to three of fermentation is known as the latent phase as the yeasts adapt to the environment.[8] Days three to six is the exponential growth phase where there is a rapid period of yeast growth and one-third of ethanol is formed. Towards the end of the fermentation, the yeasts will digest itself (autolysis), as well as the fatty acids, mannoproteins and amino acids. Excess carbon dioxide is removed by pouring the wine repeatedly. Oxygen is therefore introduced into the solution to assist in aging of the wine.[6]


The percentage of alcohol present in finished wine is determined by the level of sugar present in the grapes from which it is produced from.[9] Chaptalization is a technique for boosting the level of alcohol in finished wine by incorporating more sugar in the must during fermentation so the yeast will be able to convert more sugars into carbon dioxide and ethanol.[9] However, few types of yeast are able to survive an alcohol content above 16%, so that is why wine does not contain a high percentage of alcohol. Following fermentation of wine, the finished product is pasteurized at 176 degrees Fahrenheit and for one minute to kill off any bacteria and unwanted microorganisms and to extend shelf life.[5]

Malolactic Fermentation

Although yeasts are dominant in wine and are the basis for alcoholic fermentation, lactic acid bacteria induces malolactic fermentation.[3] Malolactic fermentation reduces the acidity of the wine by converting malic acid to lactic acid, giving it a wholesome flavour.[3] For every malic acid converted to lactic acid, one carbon dioxide molecule is formed.[8] Typically, this process is used in red wines that undergo an aging process, or even certain white wines such as Chardonnay, Pinot Blanc and Pinot Gris.[10] Benefits to malolactic fermentation are its positive contributions to microbial stability and its unique sensory characteristics.[3]

Caption: French Burgundy Wood Fermenters.

There are three families of lactic acid bacteria that are responsible for malolactic fermentation, Oenococcus oeni, Lactobacillus and Pediococcus.[3] As alcoholic fermentation occurs, the lactic acid bacteria population adapts to its environment and grows at a steady but slow rate.[3] As ethanol levels rise, Oenococcus eoni predominates the wine, which reduces the total acidity of the wine by replacing the strong flavours of malic acid with milder flavours of lactic acid.[3] In sensory terms, the increase in desirable flavors such as fruity flavors, buttery, floral, roasted, and honey aromas are linked with the formation of lactic acid bacteria esters in wine by malolactic fermentation.[3] As malolactic fermentation develops these desirable characteristics, it also reduces vegetable and grassy aromas.[11] According to many winemakers, this trait is most effective when malolactic fermentation occurs when the wine is in the barrel.[10]

Bacterial stability from malolactic fermentation stems from the consumption of available nutrients which prevent growth of other microorganisms or from bacteriocins produced, compounds toxic to other members of the same species.[8] The fact that malolactic fermentation occurs before bottling prevents bacterial growth within the bottle.[8] Malolactic fermentation within the bottle is undesirable because it may cause an increase in pH, making the environment favorable for growth to many microorganisms.[8] It can also cause turbidity, a cloudiness in the wine due to cell growth. This may even change the way the wine tastes.[8]

It is important to note that malolactic fermentation occurs minimally during alcoholic fermentation and more so after due to sulfur dioxide, which inhibits the early onset of malolactic fermentation.[12] If lactic acid bacteria exceeds 1g/L during alcoholic fermentation, its by product is acetic acid, spoiling the wine by creating high volatile and undesirable flavors.[12] According to Loncaud-Funel, this “lactic-disease” occurs during wine production and storage.[12] Many consumers do not understand the fermentation process and associate carbon dioxide bubbles within the bottle as spoilage.[8] Many also associate the cloudiness in the bottle with spoilage, making such wines undesirable.[8] Therefore, as the ethanol levels increase and peak around 14%, malolactic fermentation is inhibited and the wines are bottled.[8]

Aging & Bottling

Following the completion of fermentation processing, there is a need to remove unwanted and excess substances from the wine mixture. This collection of dead yeasts, precipitates, and plant matter settle at the bottom of containers and are referred to as the lees.[2] Removing all this sediment is crucial as it can tamper with the winemaker's desired end product by affecting sulphur balances and aromas.[1] With the goal being to separate the desired liquid wine from the unwanted lees, a process known as racking is employed whereby the relatively lighter mixture is transported to a new container with the dense and undesired sediment remaining behind.[2] While some sediments may have minorly been removed prior to malolactic fermentation, it is essential to further ensure proper turbidity before beginning the all important aging process. Consequently, racking is employed to remove the bulk of unwanted constituents, with the few remaining impurities to be filtered prior to bottling.

Caption: Aging process within barrels in a temperature controlled room.

Through the effects of aging, winemakers are able to fine-tune their product to a desired appearance and flavour. There are two substances of particular concern; sulphur dioxide and tannins, which each affect colour and taste respectively. Firstly the colour of red-wine fluctuates during maturation, and is properly established once pigments polymerize and stabilize over time. The pH balance affects colour with more acidic environments shown to favour red colour tones.[1] However prior to polymerization, sulphur dioxide can have a bleaching effect on the pigments and thus there is a delicate balance between using sulphur dioxide for anti-microbial purposes and avoiding discolouration due to its use.[1] As the pigments polymerize with time the colour is progressively less affected by the fluctuations of sulphur or pH, and the wine's identity becomes more distinguished. The goal of the winemaker is the most important factor here; when desiring young wines that are still vibrantly red an acidic environment would be preferred. If time is plenty and a full, more developed taste is desired, the pH can be higher during aging as there is less of a rush for the red pigments to stabilize.[2] Nonetheless, a low pH is the ideal environment as sulphur dioxides undesired effects are even more pronounced at higher pH levels, and as such stricter racking to eliminate micro-organisms is preferred instead of elevated sulphur levels.[1]

Now while the acidity surely affects colour and flavour to an extent, the taste the wine elicits can be significantly improved or worsened by the actions of tannins which are the source of bitterness and puckering astringency.[2] Wines possessing higher tannin levels require longer to mature, and consequently high tannin levels are associated with darker appearing wines. With time, these elevated levels of tannins begin to integrate with other components of the wine and deliver a more pleasing taste than that of immature and sharp tannins. Warmer environments have been shown to favour increased tannin levels, and as such temperature is also an important consideration during aging.[2]


Caption: Wine bottles


The storage method for aging wine is reflective once again of the winemakers goals for the product. Exposure to air and oxidative effects is an integral element of wine maturation and the degree to which this occurs is controlled by the winemaker. When given the choice between glass/steel vessels and wooden barrels, the producer desiring further maturation would opt for the wooden barrel as it allows some minor passage of oxygen.[1] The container itself can contribute oak flavours in the case of wooden barrels, and the use of fresh or used barrels is another tool in the winemakers arsenal for developing unique aromas and tastes.

Once the aging process has delivered a wine product with the taste of adequate and desired development, the final process involves ensuring the utmost clarity and removal of impurities. At this point another round of racking is an option, to remove any dense particles or precipitates. Apart from mechanically separating the pure wine product from other substances, some winemakers may choose to employ fining agents which are capable of aggregating small particles that initial racking failed to leave behind. Once the fining agent particles, egg whites for example, finish binding unwanted substances, they form a dense aggregation of sediment which another round of racking can discard with.[2] Conversely, further purification can occur through filtration whereby the liquid mixture is passed through pores corresponding to the size of the unwanted particulate matter.[2] This process leaves behind large unwanted substances, similar to what racking achieves, and the exact combinations of racking, fining and filtration are all a matter of preference that the winemaker adjusts according to the desired end product.

Wine bottling line at Chateau Ste. Michelle Winery

Ultimately the large vessel aging and filtration reaches a satisfactory stage and the wine is ready to be bottled and consumed. Depending on the extent of production and how many large tanks/carboys there are; a simple racking and fining procedure ending with a tube feeding into a bottle would be appropriate for small scale wineries while for larger ones, systems utilizing gas-powered pumping machines are efficient at filling many bottles at once. Both methods include a final round of filtration to once again guarantee vibrant clarity of the end product. Regardless of which method is employed, the bottle is usually flushed with an inert gas prior to filling as this helps in greatly reducing the amount of oxygen exposure to the wine once it reaches there.[2] After the bottle is finally filled, it can be sealed with either a cork or crown cap with each needing be stored on its side and upright respectively. However, the positive effects of aging haven't come to a complete halt and the wine still continues to develop in flavour so, winemakers and consumers alike may choose to even further delay consumption.

Wine Regulations

By global standards, Canada is relatively a small-scale producer of wine.[13] The cold climate in Canada limits productions, since only small areas of the country permit a long enough growing season.[13] With this in mind, Canada has become internationally recognized for its cold climate niche market, including Icewines and Late Harvest wines.[13] The majority of Canadian wines are grown and produced in Ontario and British Columbia.[13] The wine industry in Canada is strongly regulated, with the exception of Alberta, all wine must be distributed and sold through provincial liquor control boards.[13]

According to the Food and Drug Regulations of Canada, wine should be an alcoholic product that needs to be produced through the process of alcoholic fermentation of fresh grapes.[14] Under the Consumer Packaging and Labeling Act, wine is exempt from the requirement to provide a list of ingredients on the label.[15]

Suggested by the Food and Drug Regulations, a various number of ingredients could also be added during the manufacturing process of wine. Some of the major ingredients include yeast, concentrated grape juice, types of sugar such as fructose and glucose, yeast foods, malolactic bacteria, oak chips and particles, copper sulphate, sorbic acid, caramel, calcium sulphate, nitrogen, sulphurous acid and calcium carbonate with restricted volume.[14] During the manufacturing process, maximum level of metatartaric acid, potassium acid, or a compound that is mixed of substances such as citric acid, fumaric acid, lactic acid, and malic acid, may also be added to the wine product.[14] Furthermore, amylase, pectinase, ascorbic acid or erythorbic acid that are at their maximum level of use could also be added.[14] In addition, fining agents such as tannic acid, polyvinylpyrrolidone, activated carbon, acacia gum and substances including citric acid, metatartaric acid, potassium acid tartrate are other substances that may be added to the product.[14] For a wine to be regarded as “light,” it must be 9% alcohol content or less.[16] Also, wine referred to as “dry,” relates to a low residual sugar content level, which means that the majority of the sugar has been fermented into alcohol.[16]

Health Canada (2012) has put forth enhanced allergen wine regulations to ensure that people with food allergies and sensitivities have reliable and user-friendly information for consumers to make an informed decision. All wine with a production date of 2012 or later must state on the label if they contain any significant amount of residual protein from a food allergen, or if there are sulphite levels of 10ppm or above.[17]

Caption: Close up of VQA label on Canadian wine


BC VQA Wine Regulations

BC wines are provincially legislated under the Wines Quality Marked Regulation.[15] The VQA (Vintner’s Quality Alliance) designation assures that the wine has been grown, fermented, processed, blended and finished in BC from 100% BC fresh grapes or grape juices.[15] VQA regulations state that no vitis labrusca grape varieties are permitted.[15] Administered by the BC Wine Authority, BC VQA wines are put through rigorous chemical and taste tests, including an analysis of each chemical compound.[15] BC Wines of Distinction are also entirely produced in BC, but have not undergone the quality tasting VQA process.[15]

Reflection

After extensive research on the winemaking process, our team has only begun to realize the strict and complicated methods needed to produce a bottle of wine. The rising trend of wine is possibly due to globalization. As wine becomes more prevalent in Canada, it becomes increasingly important for consumers to understand where our food comes from and how it is regulated for our safety. Wine is originally grape juice fermented by yeast and bacteria to produce an alcoholic beverage. Because bacteria and yeast are used here for beneficial purposes, other harmful microbes might possibly contaminate the wine and cause diseases or illnesses. Additives such as sulphur dioxide are added to the wine to prevent harmful microbial growth. As commercial production of wine comes into play, it is important for each processing step to ensure extra caution in fear of health hazards.


Possible Exam Question

Question: What are the factors that contribute to increased tannin levels? Are there more in fresh younger wines or aging older wines, and why?

Answer: Increased temperature, increased aging period and increased mass of grape skins contribute to higher tannin levels.

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Dharmadhikari, M. (2000) Red Wine Production. Retrieved from http://www.extension.iastate.edu/NR/rdonlyres/173729E4-C734-486A-AD16-778678B3E1CF/73973/RedWineProduction.pdf
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Comfort, S. (2008) Guide to Red Winemaking. Retrieved from http://www.morewinemaking.com/public/pdf/wredw.pdf
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Rodríguez-Bencomo, J. J., Pozo-Bayón, M. A., & Moreno-Arribas, M. V. (2012). Wine Fermentation and Production. Handbook of Plant-Based Fermented Food and Beverage Technology, 2, 179 - 200. Retrieved March 6, 2013, from the CRCnetBASE database.
  4. ↑ Moreno-Arribas, Victoira & Polo, Carmen. (2009). Wine Chemistry and Biochemistry. Madrid, Spain: Springer.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Calwineries. (2013). Red Wine Alcoholic Fermentation. Retrieved from http://www.calwineries.com/learn/wine-production/red-wine-production/red-wine-alcoholic-fermentation
  6. ↑ 6.0 6.1 6.2 6.3 Lauren Hill. (2009). The Chemistry of Wine Making. Retrieved from http://www.emsb.qc.ca/laurenhill/science/wine.html
  7. ↑ Sablayrolles, J.M. (2008). Control of alcoholic fermentation in winemaking: Current situation and prospect. Food Research International, 42, 418-424.
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 Bisson, L. (2001). VEN124. Section 4 - The Malolactic Fermentation Lesson 12: Introduction. University of California at Davis.
  9. ↑ 9.0 9.1 Morethanorganic. (2013). Fermentation. Retrieved from http://www.morethanorganic.com/fermentation
  10. ↑ 10.0 10.1 Collings, B. (2001, December 1). Malolactic Fermentation. BCAWA - British Columbia Winemakers Association. Retrieved March 18, 2013, from http://www.bcawa.ca/winemaking/ml.htm
  11. ↑ Henick-Kling T. 1993. Malolactic fermentation. In: Fleet GH, editor. Wine microbiology and biotechnology. Berlin: Springer–Verlag. p. 286–326.
  12. ↑ 12.0 12.1 12.2 Lonvaud-Funel A. 1999. Lactic acid bacteria in the quality improvement and depreciation of wine. Antonie van Leeuwenhoek 76:317–31.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 Agriculture and Agri-Food Canada. (2012). The Canadian Wine Industry. Retrieved from http://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1172244915663#cn-tphp
  14. ↑ 14.0 14.1 14.2 14.3 14.4 Justice Laws Website.(2013). Food and Drug Regulations. Retrieved from http://laws-lois.justice.gc.ca/eng/regulations/C.R.C.%2C_c._870/
  15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 Farris Law Group. (2011). BC Wine Law A Brief Summary. Dulec, A, & Coulson, S. Retrieved from http://www.farris.com/images/uploads/ALH_-_Summary_of_BC_Wine_Law_for_Second_Annual_Wine_Law_Conference_in_BC.PDF
  16. ↑ 16.0 16.1 Canadian Food Inspection Agency. (2012). Chapter 10: Labeling of Alcoholic Beverages. Retrieved from http://www.inspection.gc.ca/english/fssa/labeti/guide/ch10e.shtml
  17. ↑ Health Canada. (2012). Vintage Wine and Application of Enhanced Allergen Regulations. Retrieved from http://www.hc-sc.gc.ca/fn-an/label-etiquet/allergen/vintage-wine-vin-millesimes-eng.php
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