• As old as wine production.French words vin ( wine ) and aigre ( sour ). It should contain > 4 % acetic acid in USA (FDA) and Turkey,> 5% acetic acid in EC.
• It is mainly used as flavoring agent, in food pickling and in medicine.
• Vinegar is produced by oxidative ( aerobic ) fermentation of ethanol in to acetic acid by Acetobacter species.( ie aceti )
• Conversion yield of ethanol to acetic acid: 95-98 %.
• During process 2-5 % of acetic acid may be over oxidized ( undesired ) to CO2 and H2O.
• stop oxidative fermentation before ethanol is completely depleted to prevent over oxidation.
• leave wine ( in a plate ) open to atmosphere, observe a film formed over the surface it is made of acetic acid bacteria ( in Turkish it is called as sirke anası ).
– Product of alcoholic and subsequent acetic fermentation of the juice of apples which contain at least 4% acetic acid (equivalents)
– 4% = 40 grain
Grain Vinegar (Distilled)
– Product of acetic fermentation of diluted, distilled grain alcohol
Factors affecting growth of acetic acid bacteria:
• Ethanol concentration should be less than 10-14 %, but if it is less than 2 %, probability of over oxidation increases.
• Different cultures can tolerate different levels of ethanol;
• 6-7 % ethanol Acetobacter oxydans, A. xylinium
• 9-11 % ethanol A. aceti, A. pasteurionum
• 11-13 % ethanol A. schutzenbachi
• ( some recently developed strains, can grow on 20 % ethanol to produce 20 g / 100 cm3 acetic acid).
• 32 g oxygen for 1 mole acetic acid.
• 1g ethanol oxidation requires 0.49 L oxygen and in turn 2.4 L air.
• During one passage of air only 1/5 of the oxygen is used which indicates that 12 liters of air is needed to oxidize 1 g ethanol.
• Optimum temperature for the growth of acetic acid bacteria is 28 – 34 C. They don’t grow at 5-10 C, show slow growth at 12- 15 C and reasonable growth at 15-28 C.
• Generally mineral and nitrogen sources is needed. ( apple juice )vinegar production 100 g ammonium sulfate is added for 1000 L.
Acetic acid :
• there are tolerance limits to acid concentration by microorganisms. Yield:0-55 parts acetate from 100 parts sugar 1.26 g acetate per 1.0 g ethanol
Production methods :
• For fast production A. schutzenbachi and A. curum is used
• and A. orleanense for slow process.
• Good acetic acid bacteria forms thin, silky film.
• Wine, grape, raisin , fruits ( apple, banana, mango, orange ,…..) malt, corn syrups, honey, sweet potato, tea, rice, coffee pulp are being used as raw material in different countries depending on availability and price.
• In Turkey vinegar is mainly produced from wine (grape Juice) or molasses.
Slow technique :