Etiket Arşivleri: Acetobacter species
• 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 :
• 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.
• -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.
• 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
• Generall concentrated by freeze concentration technique:
• to reduce transportation cost
• to be recyled and used more than once in pickling
• 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, )