Processing vinegar

Manufactured by the liquid-phase oxidation of ethanal at 60 C by oxygen or air under pressure in the presence of manganese(ii) ethanoate, the latter preventing the formation of perelhanoic acid. Another important route is the liquid-phase oxidation of butane by air at 50 atm. and 150-250 C in the presence of a metal ethanoate. Some ethanoic acid is produced by the catalytic oxidation of ethanol. Fermentation processes are used only for the production of vinegar. 

Maturation is conducted in closed, full containers to prevent oxidation and aerobic growth of microorganisms. Etee air contact with low alcohol wine soon leads to vinegar. Except for those sherry types already mentioned, wines ate exposed to air minimally and temporarily. During transfers incident to bulk storage and processing, some air exposure is almost inevitable, mote in total the longer the wine is held. In the cases of white and pink table wines, it is ordinarily as neat zero as possible, and stainless steel or other impermeable containers, inert gas headspace, etc ate employed. Red wines withstand and even benefit from small but repeated exposures to air. 

In 1973, a multistage surface-fermentation process was patented in Japan for the production of acetic acid (42) eight surface fermenters were connected in series and arranged in such a way that the mash passed slowly through the series without disturbing the film of yAcetobacter on the surface of the medium. This equipment is reported to produce vinegar of 5% acidity and 0.22% alcohol with a mean residency time in the tanks of 22 h. 

Submerged-Culture Generators. Adaptation of the surface-film growth procedure for producing antibiotics to an aerated submerged-culture process has been successful in making vinegar. A mechanical system keeps the bacteria in suspension in the Hquid in the tank, in intimate contact with fine bubbles of air. The excess heat must be removed and the foam, which accumulates at the top of the tank, must be destroyed. 

Because traces of iron reduce the brilliance of many dyes, wood tanks have long been preferred to steel in the manufacture of dyes. Similarly, vinegar and sour foodstuffs are processed in wood tanks because common metals impart a metallic taste. Ease of fabrication may be the reason for using wood tanks in less accessible areas to which ready-made tanks of other materials caimot be easily moved. 

In the early years of the chemical industry, use of biological agents centered on fermentation (qv) techniques for the production of food products, eg, vinegar (qv), cheeses (see Milk and milk products), beer (qv), and of simple organic compounds such as acetone (qv), ethanol (qv), and the butyl alcohols (qv). By the middle of the twentieth century, most simple organic chemicals were produced synthetically. Fermentation was used for food products and for more complex substances such as pharmaceuticals (qv) (see also Antibiotics). Moreover, supports were developed to immobilize enzymes for use in industrial processes such as the hydrolysis of starch (qv) (see Enzyme applications). 

Freeze Crystallization. Freezing may be used to form pure ice crystals, which are then removed from the slurry by screens sized to pass the fine sohds but to catch the crystals and leave behind a more concentrated slurry. The process has been considered mostly for solutions, not suspensions. However, freeze crystallization has been tested for concentrating orange juice where sohds are present (see Fruit juices). Commercial apphcations include fmit juices, coffee, beer, wine (qv), and vinegar (qv). A test on milk was begun in 1989 (123). Freeze crystallization has concentrated pulp and paper black hquor from 6% to 30% dissolved sohds and showed energy savings of over 75% compared with multiple-effect evaporation. Only 35—46 kJ/kg (15—20 Btu/lb) of water removed was consumed in the process (124). 

Contamination by flies may occur directly in a factory, especially if material is allowed to stand unprotected for long periods while being held for processing. Failure to dispose of refuse promptly, particularly outside the plant, frequently creates ideal breeding and feeding places for these pests. Under such circumstances, parts of the adult vinegar fly, its larvae, or eggs, when found in the comminuted product, provide definite evidence of careless and insanitary operations. 

In fermentation for the production of acetic acid, ethyl alcohol is used in an aerobic process. In an ethanol oxidation process, the biocatalyst Acetobacter aceti was used to convert ethanol to acetic acid under aerobic conditions. A continuous fermentation for vinegar production was proposed for utilisation of non-viable A. aceti immobilised on the surface of alginate beads. 

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). 

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