2. Vinegar (acetic acid)
An organic acid: the organic compounds containing
carboxylic group (COOH). These are primary
metabolite.
Vinegar is a product resulting from the conversion of
alcohol to acetic acid by acetic acid bacteria,
Acetobacter and Gluconobacter.
Vinegar: an aquous solution of acetic acid, produced
in fermentation by oxidation of a dilute ethanol
solution.
Household vinegar (13% acetic acid)
3. Uses of vinegar
Ancient uses:
Food condiment
Treatment of Wounds
Wide variety of illnesses such as plague, ringworms, burns,
lameness
Cleansing agent
Used as a cosmetic aid
Modern uses:
Food condiment, sprinkled on certain foods such as fish at the table
For pickling and preserving meats and vegetables; it can reduce the
pH of food below that which even spore formers may not survive
Manufacture of sauces, salad dressings, mayonnaise, tomato
productions, cheese dressings, mustard, and soft drinks
4. Various Major Vinegars
The composition and specifications of various types of vinegars are defined by
regulations set up by the governments of different countries
In the United States, for example, vinegar should not contain less than 4.0% (w/v)
acetic acid and not more than 0.5% ethanol (v/v)
Types: i) Cider vinegar, apple vinegar: Vinegar produced from fermented apple
juice and non-grape fruits
(ii) Wine vinegar, grape vinegar: Fermented grape juice
(iii) Malt vinegar: Produced from a fermented infusion of barley malt with or
without adjuncts
(v) Spirit vinegar: Vinegar made from distilled alcohol
Some specialty vinegars: formulated or flavored to provide a special or
unusual taste when added to foods
5. Biochemical changes
1) Alcoholic fermentation of carbohydrate
2) Oxidation of alcohol into acetic acid
Ethyl alcohol + 2 Oxygen 2 Acetic acid +2 Water
7. The bacteria converting alcohol to acetic acid under natural conditions are
film forming organisms on the surface of wine and beer
The film was known as ‘mother of vinegar’ before its bacteriological nature
became known
The bacteria were first described as Mycoderma (viscous film) in 1822.
Later other workers classified them in M. vini (forming film on wine) an M.
acetic (forming film on beer).
Pasteur confirmed that acetic acid is produced only in the presence of the
bacteria, but he did not identify them.
The genus name Acetobacter was put forward by Beijerinck in 1900.
Although Acetobacter spp are responsible for vinegar production, pure
cultures are hardly used, except in submerged fermentation because of the
difficulty of isolating and maintaining the organisms.
Microorganism involved
8. Strains of acetic acid bacteria to be used
in industrial production should
Tolerate high concentrations of acetic acid
Require small amounts of nutrient
Not over-oxidize the acetic acid formed
Be high yielding in terms of the acetic acid
produced
9. MANUFACTURE OF VINEGAR
Three methods used for the production of vinegar
1. The Orleans Method (also known as the slow
method)
2. The Trickling (or quick) Method
3. Submerged Fermentation (Main method)
10. Submerged Fermentation:
The common feature in all submerged vinegar production is that
the aeration must be very vigorous as shortage of oxygen because
of the highly acid conditions of submerged production, would result
in the death of the bacteria within 30 seconds.
Furthermore, because a lot of heat is released (over 30,000 calories
are released per gallon of ethanol) an efficient cooling system
must be provided
All submerged vinegar is turbid because of the high bacterial
content and have to be filtered.
11. Frings acetator:
Most of the world’s vinegar is now produced with this fermenter.
It consists of a stainless steel tank fitted with internal cooling coils and a
high-speed agitator fitted through the bottom.
Air is sucked in through an air-meter located at the top.
It is then finely dispersed by the agitator and distributed throughout the
liquid.
Temperature is maintained at 30°C, although some strains can grow at a
higher temperature.
Foaming is interrupted with an automatic foam breaker.
Essentially it is shaped like the typical aerated stirred tank fermenter.
It is operated batch-wise and the cycle time for producing 12% vinegar is
about 35 hours
13. The hollow rotor is installed on the shaft of a motor mounted under
the fermenter, connected to an air suction pipe and surrounded by
a stator
It pumps liquid that enters the rotor from above outward through
the channels of the stator that are formed by the wedges, thereby
sucking air through the openings of the rotor and creating an air–
liquid emulsion that is ejected outward at a given speed
This speed must be chosen adequately so that the turbulence of
the stream causes a uniform distribution of the air over the whole
cross section of the fermenter
14. Advantages
The efficiency of the acetator is much higher than that of the trickling
generator; the production rate of the acetator may be 10-fold higher
than a trickling unit
The quality is more uniform and the inexplicable variability in quality
noted for the trickling generator is absent
A much smaller space is occupied (about one-sixth) in
comparison with the trickling generator.
It is easy and cheap to change from one type of vinegar to
another.
Continuous production and automation can take place more
easily with Fring’s acetator than with trickling
Editor's Notes
acetic CH3CO2H, colorless liquid; pungent odor, boils at 118°C; it is a weak organic carboxylic acid.
Glacial acetic acid is concentrated, 99.5% pure acetic acid; it solidifies at about 17°C to a crystalline mass resembling ice.
Acetic acid is also a product in the destructive distillation of wood.
Vinegar consists of acetic acid (CH3COOH), water and trace amounts of other chemicals, which may include flavorings. The concentration of the acetic acid is variable. Distilled vinegar contains 5-8% acetic acid.
The name is derived from French (Vin = wine; Aigre-sour or sharp) and one of the oldest known fermentation.
an adjunct is an optional, or structurally dispensable, part of a sentence, clause, or phrase that, if removed or discarded, will not otherwise affect the remainder of the sentence
Conversion of ethanol to acetaldehyde by alcohol dehydrogenase (enzyme)
Conversion of hydrated acetaldehyde to acetic acid by acetaldehyde dehydrogenase (enzyme)
acetaldehyde dehydrogenase
Conversion of ethanol to acetaldehyde by alcohol dehydrogenase (enzyme)
Conversion of hydrated acetaldehyde to acetic acid by acetaldehyde dehydrogenase (enzyme)
Acetic acid bacteria (AAB) are a group of gram-negative bacteria which oxidize sugars or ethanol and produce acetic acid during fermentation.[
Yeast (Vin13, N96, and Vin7)
Yeast (EC1118, V1116, and 71B)
All acetic acid bacteria are rod-shaped and obligate aerobes.
Gluconobacter, do not further oxidize acetic acid, as they do not have a full set of Krebs cycle enzymes.
One species of Acetobacter, Acetobacter xylinum, is able to synthesize cellulose,[3] something normally done only by plants.
pH 2.4
Acetic acid is the second simplest carboxylic acid (after formic acid) and is an important chemical reagent and industrial chemical, mainly used in the production of cellulose acetate for photographic film and polyvinyl acetate for wood glue, as well as synthetic fibers and fabrics.
Acidophile (pH <=3)
Some genera, such as Acetobacter, can oxidize acetic acid to carbon dioxide and water using Krebs cycle enzymes. Other genera, such as Gluconobacter, do not further oxidize acetic acid, as they do not have a full set of Krebs cycle enzymes.
obligate aerobes
It is self aspirating, no compressed air being needed
The stator is the stationary part of a rotary system, found in electric generators, electric motors, sirens, or biological rotors.
Microbial production of alkaloids and polysaccharides
Well-known alkaloids include morphine, strychnine, quinine, ephedrine, and nicotine
Amylose (starch), Amylopectin, Glycogen (animal storage polymer), Cellulose