| Winemaking, or vinification, is the process of wine | | | | often visible as a powdery appearance of the |
| production, from the selection of grapes to the | | | | grapes. The fermentation can be done with this |
| bottling of finished wine. | | | | natural yeast, but since this can give unpredictable |
| After the harvest, the grapes are crushed and | | | | results depending on the exact types of yeast |
| allowed to ferment. Red wine is made from the | | | | that are present, cultured yeast is often added to |
| must (pulp) of red or black grapes that undergo | | | | the must. |
| fermentation together with the grape skins, while | | | | During the primary fermentation, the yeast cells |
| white wine is usually made by fermenting juice | | | | feed on the sugars in the must and multiply, |
| pressed from white grapes, but can also be made | | | | producing carbon dioxide gas and alcohol. The |
| from must extracted from red grapes with | | | | temperature during the fermentation affects both |
| minimal contact with the grapes' skins. | | | | the taste of the end product, as well as the |
| Rosé wines are | | | | speed of the fermentation. For red wines, the |
| made from red grapes where the juice is allowed | | | | temperature is typically 22 to 25 |
| to stay in contact with the dark skins long enough | | | | °C, and for white |
| to pick up a pinkish color, but little of the tannins | | | | wines 15 to 18 °C. |
| contained in the skins. | | | | For every gram of sugar that is converted, about |
| During this primary fermentation, which often | | | | half a gram of alcohol is produced, so to achieve |
| takes between one and two weeks, yeast | | | | a 12% alcohol concentration, the must should |
| converts most of the sugars in the grape juice | | | | contain about 24% sugars. The sugar percentage |
| into ethanol (alcohol). After the primary | | | | of the must is calculated from the measured |
| fermentation, the liquid is transferred to vessels | | | | density, the must weight, with the help of a |
| for the secondary fermentation. Here, the | | | | saccharometer. If the sugar content of the |
| remaining sugars are slowly converted into alcohol | | | | grapes is too low to obtain the desired alcohol |
| and the wine becomes clear. Some wine is then | | | | percentage, sugar can be added (chaptalization). In |
| allowed to age in oak barrels before bottling, | | | | commercial winemaking, chaptalization is subject |
| which add extra aromas to the wine, while others | | | | to local regulations. |
| are bottled directly. The time from harvest to | | | | During or after the alcoholic fermentation, |
| drinking can vary from a few months for | | | | malolactic fermentation can also take place, during |
| Beaujolais nouveau wines to over ten years for | | | | which specific strains of bacteria convert malic |
| certain Bordeaux wines. However, most wine on | | | | acid into the milder lactic acid. This fermentation is |
| the market tastes best between one and three | | | | often initiated by inoculation with desired bacteria. |
| years after the harvest. | | | | With red wines, the must is pressed after the |
| Variations on the above procedure exist. Sweet | | | | primary fermentation, which separates the skins |
| wines are made by ensuring that some residual | | | | and other solid matter from the liquid. With white, |
| sugar remains after fermentation is completed. | | | | and rosé wine, |
| This can be done by adding a substance to kill the | | | | there is no need to press. The wine is separated |
| remaining yeast, such as port wines where a high | | | | from the dead yeast (called its lees), and |
| proof brandy is added well before the | | | | transferred to a new container for its secondary |
| fermentation is completed. In other cases the | | | | fermentation. |
| winemaker may choose to hold back some of | | | | Secondary fermentation and Bulk Aging |
| the sweet grape juice and add it to the wine | | | | During the secondary fermentation and aging |
| after the fermentation is done, a technique known | | | | process, which takes three to six months, the |
| as süssreserve. | | | | fermentation continues very slowly. The wine is |
| With sparkling wines such as Champagne, an | | | | kept under an airlock to protect the wine from |
| additional fermentation takes place inside the | | | | oxidation. Proteins from the grape are broken |
| bottle, trapping carbon dioxide and creating the | | | | down and the remaining yeast cells and other fine |
| characteristic bubbles. | | | | particles from the grapes are allowed to settle. |
| The grapes | | | | Potassium bitartrate will also preticipate, a process |
| Of all factors affecting the quality of a wine, the | | | | which can be enhanced by cold stabilization to |
| quality of the grapes more than any other factor | | | | prevent the appearance of (harmless) tartrate |
| determines the quality of the wine. Their quality is | | | | crystals after bottling. The result of these |
| not only affected by their variety, but also by the | | | | processes is that the originally cloudy wine |
| weather during the growing season, the soil, the | | | | becomes clear. The wine can be racked a during |
| time of harvest, and the way they are pruned. | | | | this process to remove the lees. |
| The combination of these effects is often | | | | The secondary fermentation usually takes place in |
| referred to as their terroir. | | | | either large stainless steel vessels with a volume |
| The grapes are usually harvested from the | | | | of several cubic meters of wine, or oak barrels, |
| vineyard in the fall, in the northern hemisphere | | | | depending on the goals of the winemakers. |
| from the middle of October until the beginning of | | | | Amateur winemakers often use glass carboys |
| November, or the middle of February until the | | | | with a capacity of 5 to 25 liters (1 to 6 gallons) to |
| beginning of March in the southern hemisphere. | | | | produce their wine. The vessel used for the |
| Crushing and primary fermentation | | | | process depends on both the amount of wine |
| In smaller-scale wine making, the harvested | | | | that is being produced, the grapes being used, and |
| grapes are sometimes crushed by trampling them | | | | the goals of the winemaker. |
| bare-footed. However, in larger wineries, a | | | | Blending and Bottling |
| mechanical crusher/destemmer is used. Because | | | | Different batches of wine can be mixed before |
| the stems of the grapes have a relatively high | | | | bottling in order to achieve the desired taste. The |
| tannin content, they are usually removed | | | | winemaker can correct perceived inadequacies by |
| beforehand. However the winemaker can decide | | | | mixing wines from different grapes and batches |
| to leave them in if the grapes themselves contain | | | | that were produced under different conditions. |
| less tannin than desired. For red wine, the broken | | | | These adjustments can be as simple adjusting |
| skins stay in contact with the juice (maceration) | | | | acid or tannin levels, to as complex as blending |
| throughout the fermentation process, while for | | | | different varieties or vintages to achieve a |
| white wines, the crushed grapes are pressed to | | | | consistent taste. |
| ferment the wine without the skins. In the case | | | | A final dose of sulfite is added to help preseve |
| of rosé wines, the | | | | the wine and prevent unwanted fermentation in |
| dark skins are left in contact with the juice just | | | | the bottle. The wine bottles then are traditionally |
| long enough to extract the color that the | | | | sealed with a cork, although alternative wine |
| winemaker desires. The must is then pressed, and | | | | closures such as synthetic corks and screwcaps, |
| fermentation continues as if the wine maker was | | | | which are less subject to cork taint, are becoming |
| making a white wine. | | | | increasingly popular. |
| Yeast is normally already present on the grapes, | | | | |