Industrial microbiology

Wine Production

Types of Wine Depending on the type of grape, yeast strain, fermentation process, etc., there are a variety of wines. There are...

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This article writter by MN Editors on November 16, 2022

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Wine Production
Wine Production
  • Since the 15th century, wine production and consumption have flourished, and contemporary science and technology have enhanced the industrial and global wine production.
  • It is thought that wine originated in the Northern Zagros Mountains of Iran approximately 4000 BCE. Although an exact date and time of the previous era has not yet been discovered.
  • Depending on the alcohol content, wine is made from fruits such as berries, apples, grapes, cherries, palm, and rice that are partially or totally fermented.
  • Vitis labrusca and Vitis vinifera are the most common grapes used in winemaking because they have all the necessary elements, including pulp, juice, and seeds that include important acids, sugars, minerals, tannins, and vitamins.
  • Viticulture is a discipline of horticulture that cultivates and harvests wine grapes, whereas enologists research the winemaking and breeding processes, as well as fermentation.

Types of Wine

Depending on the type of grape, yeast strain, fermentation process, etc., there are a variety of wines. There are so many differences amongst them that it becomes impossible to classify them accurately. However, the following are notable wine varieties:

1. Red wines

  • This category is reserved for wines with a red hue. Grapes are crushed and de-stemmed during preparation, but their skins and seeds are left in the “must.”
  • The alcohol concentration of these wines is between 11 and 12.
  • Rose wines, Burgundy wines, Claret wines, Vinorosso wines, etc. are some examples.

2. Dry wines

  • These wines contain so little sugar that it cannot be detected by taste, i.e., the sugars are nearly completely fermented.
  • The alcohol content in dry wines ranges from 19 to 20 percent.
  • Examples: Post, Takay, and Muscatel wines, among others.

3. Sweet wines

  • These wines are “sweet wines” because they contain significant amounts of unfermented sugars.

4. Sparkling wines

  • These are the wines that undergo secondary fermentation in sealed containers that contain carbon dioxide.
  • Likewise, they contain 11-12% alcohol.
  • Sparkling Burgundy, Champagne, etc. are examples.

5. Still wines

  • Still wines are wines that do not contain carbon dioxide. There is 12-15% alcohol content.
  • Sherries, Vermouth, etc. are examples of such alcoholic beverages.

6. Fortified wines

  • These wines have brandy as an extra alcoholic ingredient.

Steps of wine making

1. Harvesting of fruits

  • Appropriate assortment of fruits and berries is gathered.
  • They must have a high concentration of fermentable carbohydrates.
  • Typically, grapes contain 5-25% of total soluble sugar (Total soluble sugar).

2. Crushing and extraction

  • Thus, obtained fruits are mechanically crushed and extracted.
  • This technique produces juice and a small amount of colour.
  • The entire mass is referred to as Must.
  • For the manufacture of white wine, the skin is removed. For the preparation of white wine, the harvested fruit is de-steamed, whereas red wine preparation does not require this step.
  • Due to the presence of 2 methoxy-3-isopropyl pyrazine, red wine’s steam has a vegetal odour.
  • Also taken from steam is colour.
  • For red wine, the Must must undergo fermentation.

3. Optimization

  • The must is optimised for the TSS and pH values.
  • TSS is typically tuned between 17 and 22%, and pH between 3 and 4, depending on yeast strains.
  • KNS (potassium metabisulphite), an antibacterial agent against Acetobacter spp. and competitive yeast, may or may not be added at this stage.
  • In addition, it has antioxidant and antifungal properties.

4. Primary fermentation

  • The optimised Must is inoculated with 2% to 10% inoculum and fermented at the optimal temperature.
  • Preparation of red wine = 22-27oC for 3-5 days
  • White wine preparation = 10 to 21 degrees Celsius for 7 to 14 days
  • During fermentation, the liquid is changed twice per day by pounding the floating skin to ensure enough aeration.
  • Additionally, it aids in colour extraction.
  • This fermentation allows for the rapid expansion of yeast cells as well as the conversion of sugar to ethanol; once the TSS has reduced to between 9 and 10 percent, the primary fermentation is complete.

5. Pressing

  • Must is stripped of its skin and pressed to extract juice and alcohol.
  • The liquid is transferred back into the tank.
  • Prior to fermentation, pressing is performed for white wine.
  • The colour of fruits and berries is removed during pressing.

6. Heat and cold sterilization

  • The primary objective of this method is to eliminate tartarate crystals (wine diamonds or wine crystals).
  • In cold sterilisation, the fermented must is cooled to near-freezing temperatures and stored for one to two weeks.
  • During this time, crystals are separated or churned in the fermenter’s wall, and clear liquid is collected in the secondary fermented tank.
  • In the heat stabilisation method, the substance is heated between 50 and 60 degrees Celsius for an hour and stored overnight.
  • The proteins are filtered.
  • The clear liquid is pumped out, and the remaining murky stuff is adsorbed onto bentonite.

7. Secondary fermentation

  • It is conducted in stainless steel or oak barrels or a plastic-lined concrete tank.
  • The stabilised, sanitised wine is now stored at 15-20oC for 3 to 6 months under strict anaerobic conditions. Typically, the fermentation of sweet wines is ended when the sugar concentration falls to 4-6%.
  • During the secondary fermentation, aromas are produced.
  • There are three distinct scent categories for wine:
  • Primary aroma: Fruits and berries contribute primarily to the scent.
  • Secondary aroma: fragrance produced by secondary fermentation
  • Tertiary aroma: generated with ageing in the bottle
  • The fragrance component may or may not be volatile.
  • It results from chemical reactions between acids (malic acid, citric acid, etc.), sugars, alcohols, and phenolic chemicals.
  • Methoxyparazine, monoterpenes, nor-isoprenoids, thiols, esters, etc. are responsible for aroma, with ester being the most important.
  • Very slowly, a reaction between alcohols and acids produces esters.
  • It takes almost a year for secondary fermentation to occur.
  • Malolactic fermentation precedes secondary fermentation.
  • Malic acid (sharp sour) —–Lactic acid bacteria (LAB)—-> Lactic acid

8. Laboratory testing

  • After secondary fermentation, a number of laboratory tests are performed, including bricks reading, bricks pH, titrable acidity, residual sugars, free or available sulphur, total sulphur, volatile acidity, and alcohol %.

9. Blending and fining

  • It is of the utmost importance to produce wine of exceptional flavour and aroma.
  • In the blending process, spices, aromatic plant extracts, essential oils, fruit juices, and other ingredients are added in proportion.
  • Blending is a winery trade secret (wine industry).
  • In order to produce a transparent wine, tannins and minute particles are extracted during the fining process.
  • To achieve this, wine is treated with gelatin, potassium caseinate, egg albumin, lysozymes, skim milk powder, etc., or filtered with a membrane filter or diatomaceous earth cellulose filter.
  • Utilizing the pectinase enzyme, wine is clarified in order to eliminate pectin.

10. Preservation

  • Primarily, pasteurisation and KMS (Potassium metabisulphite) are employed for preservation.
  • It eliminates sugar using microorganisms.

11. Bottling

  • The final step is aseptically filling the bottle with wine and corking it with an oak cork.
  • The exterior cork is then sealed.
  • The wine can be enjoyed immediately or stored.
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