Acetobacter wines

The sugars in fruits such as grapes are feimented by yeasts to produce wines. In winemaking, lactic acid bacteria convert malic acid into lactic acid in malolactic fermentation in fruits with high acidity. Acetobacter and Gluconobacter oxidise ethanol in wine to acetic acid (vinegar). 

Immobilization is the technique of choice in many food industry processes and especially in beverage production. Many immobilization technologies have already been tested and some are applied in the production of beer, wine, vinegar, and other food products using a traditional approach with cultme adhesion (i.e., Acetobacter in vinegar production) or more modem approaches with entrapment of yeast biomass (i.e., sparkling wines, cheeses, and yogurts). 

Acetobacter bacteria oxidatively convert wine to vinegar through an aerobic fermentation of ethanol (a primary alcohol) into acetic acid (a carboxylic acid) ... 

Human use of acids and bases dates back thousands of years. Probably the first acid to be produced in large quantities was acetic acid, HC HjO. Vinegar is a diluted aqueous solution of acetic acid. This acid is an organic acid that forms when naturally occurring bacteria called acetobacter aceti convert alcohol to acetic acid. Ancient Sumerians used wine to produce vinegar for... 

Ethyl acetate is a product of yeasts and a normal component of wine. Its level can be increased by Acetobacter contamination, although most wines showing excess volatile (acetic) acid do not necessarily contain excess ethyl ester initially. It is quite possible to obtain brandy of normal composition and quality by continuous distillation of newly fermented wine containing excess acetic acid, e.g., 0.1%. On the other hand, ethyl acetate can be formed in continuous columns, particularly if the distillation conditions provide for a relatively high ethanol concentration on the feed tray or immediately below. Since acetic acid is weakly yolatile in all mixtures of ethanol and water, it does not appreciably distill upward. Therefore there is no opportunity for acetic acid to combine wtih ethanol in tray liquids normally of high ethanol concentration. 

Orleans Process, In the Orleans process, wine oxidizes slowly in a barrel where it is covered with a film of Acetobacter. Holes that are covered with screens to exclude insects are bored in each barrel head to permit... 

Submerged-culture oxidizers are usually operated on a semicontinuous basis. In most cases, ca half the liquid in the tank is removed every 1-2 d, when the alcohol concentration has dropped to 0.1-0.2 vol %. The removed vinegar is replaced with wine or mash of richer ethanol and lower acetic acid concentration, giving a mixture in the tank of 5-6 vol % ethanol and 6-8 vol % of acetic acid. These arc the optimum conditions for Acetobacter gr owth. 

Acetic acid represents the only organic acid of normal olfactory sensory significance to wines (27). While acetic acid may be formed by . cerevisiae, the concentrations produced are typically less than 300 mg/L (55), far lower than the concentrations produced by spoilage microorganisms (he, Acetobacter) which are the predominate source (52). Apiculate yeasts may also serve as a source of acetic acid Romano et ah (36) found that Kl apiculata typically produced greater than 200 mg/L acetic acid in synthetic medium fermentations. 

Vinegar Cider, wine Acetobacter species Worldwide... 

Numerous bacterial species are present during the vinification process. The extent to which these species grow determines the types and concentrations of many substances that contribute to the aroma and flavor of a wine. Growth of bacterial species such as Acetobacter Gluconobacter, Lactobacillus, and Pediococcus may cause spoilage of a wine through the production of... 

For larger scales, shallow trays made of corrosion-resistant metal or plastic placed in portable trolleys may be used for efficient liquid-air contact. The trolleys are placed in a sterile room with frequent sterile air changes under closely controlled temperature and humidity conditions. Efficient air-liquid contact may also be obtained from a loosely packed, moist, solid medium permeated with air. For instance bran is used as the substrate for enzyme production by Aspergillus oryzal. Wine vinegar (acetic acid) is produced by trickling wine (basically ethanol in water) over a short tower of wood chips, which are used both as a support and to provide air to Acetobacter aceti [13] (Eq. 16.15). By law, the acetic acid (3-5% in water) in vinegar must be produced by fermentation, and not by petrochemical methods. 

Du Toit, W.J., Pretorius, I.S., and Lonvaud-Funel, A. 2005. The effect of sulphur dioxide and oxygen on the viability and culturability of a strain of Acetobacter pasteurianus and a strain of Brettanomyces bruxellensis isolated from wine. Journal of Applied Microbiology 98 862-871. 

There are several types of acetic bacteria (Volume 1, Chapter 7) with different metabolic properties. These are responsible for serious problems due to acescence, sometimes called acetic spoilage . Wine is only affected by Acetobacter, or vinegar ferment. The main reaction consists of the oxidation of ethanol to produce acetic acid. In the presence of ethanol, this same bacterium may also esterify acetic acid to produce ethyl acetate. Acetic bacteria develop in the form of a white bloom that may take on various appearances. Prolonged development produces a viscous mass, known as vinegar mother . 

When the alcohol in wine changes into vinegar, there are two processes involved. The first one is relatively minor. Ethanol, the alcohol of beverages, reacts with oxygen to form acetic acid, a dilute solution of which we refer to as vinegar. This happens only to a very small extent, because the wine doesn t come into contact with much oxygen. What really causes wine to turn to vinegar is contamination with a bacteria called Acetobacter aceti. 

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