Vinegar Production - Role Of Microorganisms 5n2f1d

Food Microbiology II- NFSC 278 Industrial Microbiology

Vinegar

Vinegar

• A dilute solution of acetic acid produced by a two-stage fermentation process

• In the first stage, fermentable sugars are converted into ethanol by the action of yeasts • In the second stage, bacteria of the genus Acetobacter oxidize the ethanol to acetic acid

Vinegar Production Fruit

Grain, Root Crops (Starch)

Starch

Glucose + Maltose Enzymes

Fermentable Mono- & Disaccharides Alcoholic Fermentation Yeast

Glucose or Fructose

ethyl alcohol + carbon Anaerobic dioxide conditions

Ethyl Alcohol

Vinegar Production Ethyl Alcohol ACETIFICATION Acetic acid bacteria

Ethyl Alcohol

Acetic acid air

Acetic Acid

Theoretical conversion 1g glucose

0.51 g ethyl alcohol

0.67g acetic acid

Vinegar

• Production of vinegar can occur as a spontaneous fermentation • Both types of microorganisms necessary for vinegar production are commonly associated with plant products as part of their natural microflora

• pH of vinegar is 3 or below

Uses of Vinegar

Food Uses: • Individual vinegars have their own particular flavor reflecting the process by which it was made and the raw material used • It is a good solvent for the essential oils of herbs and spices and has been a sauce ingredient throughout history

Uses of Vinegar

• Vinegars flavored with tarragon, chili, garlic, rosemary and the like are produced commercially for use in home-produced marinades and salad dressings • The range of food products prepared using vinegar include: mayonnaise, ketchups, sauces, chopped pickles, brined vegetables

Uses of Vinegar

• Pickling foods in vinegar is one of the traditional technologies of food preservation • The preservative action of vinegar is due to its acetic acid content • 0.1% of the undissociated acid will inhibit the growth of most food poisoning and sporeforming bacteria

Raw Materials

• Vinegar can be made from any non-toxic raw material that furnishes a juice or solution containing fermentable sugars • A vinegar takes its name from the raw material used

• E.g. malt vinegar, wine vinegar, rice vinegar

Raw Materials

• Vinegar is an inexpensive commodity, its economic production requires a relatively low cost raw material • In most cases the raw material used contains sufficient nutrients to the growth and metabolism of acetic acid bacteria

Alcoholic Fermentations

• Normally the yeast used in alcoholic fermentation is a strain of the species Saccharomyces cerevisiae

• The transformation of a hexose by S. cerevisiae can be represented chemically by the GayLussac equation: C6H12O6 Fermentable hexose (180g)

2C2H5OH + 2CO2 Ethanol (92g)

Carbon dioxide (88g)

Alcoholic Fermentations

• The catabolism of sugar provides the yeast cell with a source of biosynthesis intermediates as well as energy

• Not all the sugar is converted to ethanol • Some of the sugar is diverted to the production of yeast cell biomass, glycerol and succinic acid

Alcoholic Fermentations

• This leads to a decrease in ethanol yield: a realistic theoretical yield would be 95%, and a good practical yield is 90% • The fermentation in vinegar production are less susceptible to microbial contamination than many other industrial fermentations • It is possible to carry it out in simple vessels such as open vats of wood or concrete

Processing of Vinegar

• After acetification, vinegar is usually matured in full closed vats for up to a year • During this time it develops its characteristic flavor and aroma and some settlement on unstable colloids takes place • Raw vinegar is normally cloudy with suspended bacteria and other particles

Processing of Vinegar

• A haze or precipitate may form in vinegars that have been in with non-acid resistant materials • This is usually due to the formation of iron and copper (metal-containing precipitates), which spoil the appearance of vinegar and make it unsuitable for use in pickling

Processing of Vinegar

• Bacterial growth and turbidity in bottled vinegar can be prevented by a heat treatment

• Gram negative acetic acid bacteria is not heat resistant, so use 600C for few minutes is enough to eliminate the numbers encountered • Product is either hot-filled into bottles after treatment or pasteurized in the bottle

Processing of Vinegar

• There is considerable advantage in producing a vinegar containing high levels of acetic acid, it is more effective in the pickling of high moisture content foods • The maximum concentration of acetic acid that can be produced by fermentation is usually around 10-15%

Vinegar Standards, Composition and Analysis

• Normally a standard identifies particular qualities associated with a foodstuff, describes the method of analysis to be used and makes some recommendations as to acceptable limits • The principal competitor of vinegar is ediblegrade synthetic acetic acid, diluted with water and usually colored with caramel

Vinegar Standards, Composition and Analysis

Acc to Codex:

Vinegar is a liquid fit for human consumption, produced from a suitable raw material of agricultural origin, containing starch, sugars or starch and sugars, by the process of double fermentation, alcoholic and acetous and contains a specified amount of acetic acid

Vinegar Standards, Composition and Analysis

• The principal quality criterion of vinegar is the acetic acid content, the minimum level is usually set at 4% (w/v) • Many bottled vinegars normally contain 5% • The determination of acidity cannot distinguish between a true vinegar and diluted acetic acid!