VINEGAR PRODUCTION

• 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 ).

Cider Vinegar

– 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:

• 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).

Oxygen:

• 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.

Temperature :

• 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.

Other
nutrients :

• 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.

1. Slow technique :

simple system:

• the first method used for vinegar production.

• A 200-300 L keg ( which contain 2-3 cm diameter holes plugged with cotton ) or wooden tray is filled with wine and vinegar ( unpasteurized  ) and incubated at 28-30 C.

• take 6-8 weeks to complete fermentation.

• A film will form on the surface of solution and when it sinks, it will be indication of the end of fermentation.

• stop fermentation when ethanol concentration is  0.5-1 % to prevent over oxidation.

• We can remove vinegar from bottom (  density of acetic acid > ethanol ) and add new wine from top through a funnel without disturbing film on the surface, otherwise production will slow down.

            Orleans Process  —slow process

– Barrel fermentation

– Holes drilled to aerate

– Starter added from previous batch

– 1/4 to 1/3 drawn off at 3 month intervals and replaced with fresh hard cider

– Results in “aged” vinegar of excellent quality

            Fast Process – generator– commonly used in Turkey

• good vinegar passed through system to have acetic acid bacteria on wood shavings.

• spray wine from top periodically , while it is flowing down, it is being converted to acetic acid.

• Several recycle should be sufficient to complete conversion to acetic acid.

•  Whole corn ( after corn kernels removed ) commonly used instead of wood shavings

• If pine tree shavings is going to be used , it should be washed with Na2CO3 to remove resins

Submerged culture method  ( acetators)

• much faster than trickling process.

• stainless steel tank

• temp., acid,  ethanol, air flow rate are controlled.

 Advantages;

• -less space,– high yield  ( 90-95 %)

• -easy to switch from one type of vinegar to other

• -highly automated,-higher quality vinegar

• -if two acetators used, 19-20 % acid production

• -product is more turbid than trickling because woods shavings act like filter and # of bacteria is higher ( disadvantage )

• monitor air bubbles

• be uniform and approximately 1 mm in diameter.

• One run  36 hours.

• not use SO2 during production of wine if it is going to be converted to vinegar.

• In pickling industry; white distilled vinegar is used because it is cheaper, high acid concentration vinegar (  to reuse it ).

• keep full during aging to prevent overoxidation.                                            

• For clarification; filtration

• Nowadays cross flow and parallel flow ultrafiltration techniques are being used ( aroma compounds, acid and sugar passes through the membrane but not the protein and pectins which causes turbidity.)

• If turbidity is high, it is first treated with gelatin and  then decantation is performed.

• Filtered vinegar is pasteurised at 60-65 C for 30 minutes then cooled to 33-38 C and bottled.

• In USA and EC only glass bottles are allowed.

Balsamic vinegar

• the juice of white grapes  boiled down to  50% of its original volume to create a concentrated must, which is then fermented with a slow aging process which concentrates the flavours.

• The flavour intensifies over decades, with the vinegar being kept in fine wooden casks, becoming sweet, viscous and very concentrated.

• the liquid is transferred to successively smaller casks made of different woods, absorbing the flavour characteristics of each wood and becoming more concentrated with each transfer.

• a small (100 ml) bottle can cost between US $100 and $400.

• less expensive varieties may not be aged in wood at all, being nothing more than ordinary wine vinegar with coloring and added sugar.

• Color: Dark brown

• Density: Fluid and syrup like consistency

• Fragrance: Distinct, complex, sharp and unmistakably but pleasantly acid

• Flavor: Traditional and inimitable sweet and sour in perfect proportion. To the taste buds it will offer a full and rich flavor with a variety of shadings and evolving bursts of new expressions as the mood or the carrier chan

• Use few drops; very expensive

Vinegar

• Generall concentrated by freeze concentration technique:

• to reduce transportation cost

• to be recyled and used more than once in pickling

Vinegar defects

• Metal ions like iron, copper cause turbidity.

• Tannin and iron forms iron tannat complex which cause blue-black turbidity

• Anguillula aceti ( vinegar eel) bad flavor upon putrefaction, (to prevent filter, pasteurize)

• Tyroglyphas longior ( vinegar mite) ( steaming)

• Acetobacter xylinium ( slime ,clogs filters, )