Are wines made by distillation or fermentation


Fermentation is the conversion of organic substances by enzymes or microorganisms. The substances are transformed into compounds with a simpler molecular structure. There are different forms of fermentation, which are named after the resulting product. During alcoholic fermentation, for example, sugar is converted into alcohol and carbon dioxide. Fermentation, like breathing, is a metabolic process that releases energy. In contrast to breathing, however, the carbohydrates are not completely broken down into water and carbon dioxide. In the human intestine, special bacteria ferment the undigested carbohydrates. The resulting gases such as hydrogen sulfide and carbon dioxide can cause gas and pain. The production of biogas by methane bacteria is also a fermentation process.



When fermenting grape juice with yeast, a gas is formed,
which causes a white cloudiness when discharged into lime water.

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Fermentation processes when baking bread

The yeast used to bake bread consists of a unicellular fungus that does not produce any fruiting bodies. When kneading the dough with water and flour, the gluten swell in the dough. This makes the dough absorbent for gases. The optimal temperature for yeast fermentation is around 32 ° C. When oxygen is present, the yeasts gain energy through respiratory processes. In the absence of oxygen under anaerobic conditions, the yeasts succeed in this through alcoholic fermentation of sugar into ethanol and carbon dioxide. However, the yeast cannot process the starch in the dough; instead, the flour provides the enzymes required to break down the starch, the amylases. The resulting breakdown products of the starch are used by the yeast for fermentation.



Yeast cells under the microscope


The resulting carbon dioxide causes the dough to swell. In a well-rising dough, 3.5 liters of gas are formed per kilogram of dough mass. During bread baking, the volatile components such as ethanol and carbon dioxide escape and allow the dough to swell further, so that the desired porosity of the bread is achieved. The heat creates the typical flavors in bread. A large part of the starch is also converted into sugar, which is partially caramelized under the heat and forms the brown rind.

At the sourdough Lactic acid bacteria produce lactic acid from saccharified starch when the dough is proofed. This lactic acid fermentation also produces small amounts of acetic acid and ethanol.

With various additives such as milk, sugar and oil one tries to make bread with certain properties. This targeted approach to fermentation is called fermentation designated. With flat breads, the dough is formed into flat shapes and baked without previous fermentation.


Alcoholic fermentation

The principle of making drinkable alcohol has been known since ancient times. Alcoholic fermentation takes place everywhere in nature when popped fruit or sweet juices are exposed to certain conditions. In technical processes, the starting material often has to be saccharified first. In the Beer making barley grains are first made to swell and germinate with water. The existing enzymes - the amylases - convert the starch into sugar when heated. This is how you get the rich maltose malt. The brewer's yeast can only ferment this. Light brewing malt is only obtained from barley, it is the most commonly used malt for beer production. Caramel malt (or caramel malt) contains sugar produced by caramelization and no longer fermentable. This is used to make full-bodied festival beer with a certain sweetness. According to the old German purity law, only barley (or malt made from barley), hops and water may be used for beer production. Today this requirement is no longer binding, but there are again breweries that advertise it and do not add any additional sugar. Up to 60% wheat malt is used to produce wheat beer.



Hops and various types of malt for making beer


After separating the insoluble residues, the resulting solution is the Spice, cooked in the simmering pan (also called "brew kettle") with the hop cones. The pans used to be made of copper. Further aromas, bitter and tannins get into the wort through boiling. After the residues have been sieved off, the intermediate product is first cooled and then enters the fermentation vat in the fermentation cellar.



Copper brew kettle in a brewery


The fermentation of sugars such as glucose, fructose or maltose into ethanol is controlled by yeast fungi and yeast enzymes. These are found practically everywhere in the air. They are also added when making beer. Fermentations can take place at different temperatures. In simplified terms, alcoholic fermentation can be illustrated using the example of grape sugar with the help of yeasts:

glucose Ethanol + carbon dioxide
C.6H12O6  2 C2H5OH + 2 CO2    DHR. = −105kJ / mol
 
The resulting ethanol is the product of a relatively complex chemical reaction with numerous intermediate steps. First, the glucose is converted into pyruvic acid in ten different steps. This reacts with the elimination of carbon dioxide again in several intermediate steps to form ethanal, which is then finally reduced to ethanol:




The resulting carbon dioxide causes foaming during fermentation. During beer production, this foam gradually turns brown due to impurities. The product is then subjected to secondary fermentation, which can take up to four months, while the main fermentation is completed after eight to ten days. For top-fermented beers, fermentation takes place at 12 to 15 ° C, for bottom-fermented beers at 5 to 10 ° C.



Foaming during beer production


To Winemaking it requires grapes that develop as fruit bunches of the grapevine. Red wine can be made from the dark blue grapes, while the yellow-green berries are used to make white wine. In the leaves of the grapevine, sugar and oxygen are formed from carbon dioxide and light through photosynthesis. The sugar content in the grapes must have a good balance with the acidity. The soil determines the aroma.



The stalks are removed from the grapes in the destemmer.


After the harvest, the grapes are first freed from the stems in the destemmer and crushed to a pulp. This is how you get the mash. Then 0.1 liters of 5% sulfurous acid are added per 100 liters of mash. This serves to kill bacteria and natural yeasts so that fermentation can take place in a controlled process with cultivated culture yeasts. The Oechsle degree measures the dissolved substances in the mash. Since the majority of these consist of sugar, the sugar content can be roughly estimated from the Oechsle grade.



Crush grapes without stems: mash.


After the culture yeast has been added, the mash is freed from the kernels and shells by pressing, so that is obtained Must. The pressed but not yet fermented must is placed in a fermentation tank. The addition of oxygen - especially at the beginning - causes the fermentation process to be initiated and optimized. This is important for the taste of the later wine. If too much oxygen is added for too long, the yeasts switch from a fermentation process to a respiratory process. The trick is to adjust the interaction between the sugar content and the addition of oxygen in an optimal ratio. During the fermentation process, the sugar content decreases, while the alcohol content increases and carbon dioxide is created.



Fermentation process in winemaking

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The longer storage in oak barrels means that certain aromatic substances from the wood get into the wine. During this cellar treatment, the wine develops its desired aroma. The amount of ethanol formed depends on the sugar content of the starting solution and on the alcohol concentration that the yeast enzymes can just bear without stopping fermentation. Therefore, beers with an alcohol content of more than six percent by volume and wines with more than 16 percent alcohol can no longer be made by fermentation. A higher concentration of alcohol can be obtained by distillation, for example in the production of brandy.



Storage of a red wine in barrels.


Lactic acid fermentation

Since humans have been feeding on the milk of pets, they have been using lactic acid fermentation to produce lactic acid. Well-known examples are yogurt products and sauerkraut. Lactic acid bacteria are found in milk and their shape can be seen under the microscope: They are spherical cocci or thin rods with a size of 0.5 to 0.8 micrometers. They are incapable of breathing, they live anaerobically without oxygen. But they don't die, even if they are exposed to oxygen. Lactic acid bacteria do not multiply in pure sugar; they need vitamins and amino acids for this. They occur in milk and milk products, as well as on plants, in the intestines and in the mucous membranes of humans. The process of lactic acid fermentation corresponds to the steps from alcoholic fermentation to pyruvic acid. Lactic acid bacteria do not have the enzyme pyruvate decarboxylase. The previously generated hydrogen reacts with the help of NAD (nicotinamide adenine dinucleotide) with pyruvic acid, which is converted into lactic acid:




Some bacteria produce the optically right-handed L (+) - lactic acid, while others only produce the left-handed D (-) - lactic acid. As a rule, however, a mixture of both lactic acids is obtained, which is known as a racemate. Through the targeted use of lactic acid bacteria, buttermilk, sour cream, sour cream butter, sour milk and yoghurt are obtained.



Lactic acid is produced during lactic acid fermentation
and little acetic acid. The solution appears cloudy.



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