The process of fermentation in winemaking turns grape juice into an alcoholic beverage. During fermentation, yeasts transform sugars present in the juice into ethanol and carbon dioxide (as a by-product). In winemaking, the temperature and speed of fermentation are important considerations as well as the levels of oxygen present in the must at the start of the fermentation. The risk of stuck fermentation and the development of several wine faults can also occur during this stage, which can last anywhere from 5 to 14 days for primary fermentation and potentially another 5 to 10 days for a secondary fermentation. Fermentation may be done in stainless steel tanks, which is common with many white wines like Riesling, in an open wooden vat, inside a wine barrel and inside the wine bottle itself as in the production of many sparkling wines.

Source: Wikipedia

The role of yeast in winemaking is the most important element that distinguishes wine from fruit juice. In the absence of oxygen, yeast converts the sugars of the fruit into alcohol and carbon dioxide through the process of fermentation. The more sugars in the grapes, the higher the potential alcohol level of the wine if the yeast are allowed to carry out fermentation to dryness. Sometimes winemakers will stop fermentation early in order to leave some residual sugars and sweetness in the wine such as with dessert wines. This can be achieved by dropping fermentation temperatures to the point where the yeast are inactive, sterile filtering the wine to remove the yeast or fortification with brandy or neutral spirits to kill off the yeast cells. If fermentation is unintentionally stopped, such as when the yeasts become exhausted of available nutrients and the wine has not yet reached dryness, this is considered a stuck fermentation

Source: Wikipedia

FERMAID O™ is an organic nitrogen source that helps to nourish yeast, improve aromas, and allows for good control over fermentation. Reliably lowers peak fermentation temperatures and improves fermentation kinetics (especially at the end of fermentation), resulting in fewer sulfur off odors like H2S. Due to FERMAID O’s highly consistent and balanced amino acid profile, the nitrogen lasts longer and less nutrient is needed than when using conventional nitrogen sources (DAP). FERMAID O use has been correlated with positive aromatic expression (thiols and esters) and enhanced mouthfeel. Blend of highly specific inactivated yeast fractions that are rich in assimilable amino acids (organic nitrogen), small peptides, essential vitamins, and minerals.

Take the ABV of Wine1 (ABV_1) and multiply it by the percent it represents of the total blend (%_1). Do this for each part, sum them up.

(ABV_1 * %_1) + (ABV_2 * %_2) + (ABV_3 * %_3) = Final ABV

a wine is considered “dry” when the wine liquid has no or very little amounts of residual sugar, usually less than 10g. The amount of residual sugar is determined by the winemaker as they decide when to stop the fermentation process.

So, if the fermentation process is interrupted before completion it will result in left-over grape sugars, hence the term “residual sugars.” Sweet wines are often made using Muscat grapes since they have a great deal of sweetness which will transfer nicely to the liquid. On the other hand, if the yeast is allowed to fully absorb all the sugar, and the fermentation process is completed, the result is a “dry” wine. A “semi-dry” or “off-dry” wine has a mild or subtle sweetness.

Traditionally Dry Wines:

Sauvignon Blanc

Chardonnay

Malbec

Pinot Noir

Tempranillo

Merlot

Pinot Grigio

Cabernet Sauvignon

Sangiovese

etc.....

Traditionally Sweet Wines:

Moscato

Port

Reisling

White Zinfandel

Sauternes

Freisa

Vouvray

etc.....

Source: Mc Clain Cellars

Lees are deposits of dead yeast or residual yeast and other particles that precipitate, or are carried by the action of "fining", to the bottom of a vat of wine after fermentation and aging.

Normally, the wine is transferred to another container (racking), leaving this sediment behind. Some wines (notably Chardonnay, Champagne, and Muscadet) are sometimes aged for a time on the lees (a process known as sur lie), leading to a distinctive yeasty aroma and taste. The lees may be stirred (French: bâtonnage) for uptake of their flavour.

Source: Wikipedia

There are a few ways to deacidify wine. One way is to use water to dilute the acidity. This method is not often used nor recommended because it can also dilute the flavor of the wine. Another way is to add Potassium Bicarbonate to the wine must.

potassium bicarbonate is recognized as a safe substance by the Food and Drug Administration in the appropriate measurements since it is also used as part of antacid medications.

Source: Wikipedia

The hydrometer has been specifically designed for the wine and beer maker. It covers a relatively broad range, and therefore, eliminates the need for several instruments of narrower ranges to get the job done. A hydrometer is an instrument for measuring the density of a liquid in relation to water. Water is given the arbitrary figure of 1.000, and other liquids are compared to this figure. The result is said to be their specific gravity (often abbreviated to SG). As you add sugar, malt extract, honey, or other soluble solids, the numbers after the decimal point increase. As the beverage ferments, the sugars are converted into carbon dioxide and alcohol which is lighter than water so the specific gravity number decreases, giving you a Final Gravity or FG.

Prevents renewed fermentation in wine that is to be bottled and/or sweetened. Use 1/2 teaspoon per gallon. When added to wine, potassium sorbate produces sorbic acid, serving two purposes: At the point when active fermentation has ceased and the wine is racked for the final time after clearing, potassium sorbate will render any surviving yeast incapable of multiplying. Yeast living at that moment will be permitted to continue fermenting any residual sugar into CO2 and alcohol, but when they die no new yeast will be present to cause future fermentation. When a wine is sweetened before bottling, potassium sorbate is used to prevent refermentation when used in conjunction with potassium metabisulfite. Please note: this product will not stop an active fermentation. Use 1/2 tsp. per gallon.

Is a common additive used to preserve and stabilize wines, ciders, and occasionally beers. When added to wine or must, it forms sulfur dioxide gas (SO2). This prevents most wild microorganisms from growing and acts as a potent antioxidant, protecting both the color and delicate flavors of wine. Potassium Metabisulfite solutions are also used as sanitizing rinses for winemaking equipment.

Usage: Dosage varies when used to kill wild bacteria in must, halt fermentation, or preserve finished wines against oxidation. The addition of ¼ teaspoon of potassium metabisulfite to 6 gallons contributes approximately 45 ppm of free SO2. To make a sanitizing rinse for equipment, dissolve 2 teaspoons of potassium metabisulfite into 1 gallon of water. You can add 1 tsp./gal. citric acid to increase the effectiveness and longevity of the sanitizing solution. High concentrations of sulfur dioxide gas are irritating and toxic, so use in a well ventilated area. After applying the solution to your equipment, allow the items to drain completely.