Acetic acid (pKa = 4.75), the primary component of vinegar, and its sodium, potassium, and calcium salts are some of the oldest food antimicrobials. Derivatives of acetic acid including diacetate salts and dehydroacetic acid have also been used as food antimicrobials. In contrast to most organic acids, acetic acid is generally more effective against yeasts and bacteria than against molds (10). Bacteria inhibited include Bacillus, Clostridium, Listeria monocytogenes, Staphylococcus aureus, and Salmonella. Only Ace-tobacter species (microorganisms involved in vinegar production), lactic acid bacteria, and butyric acid bacteria are tolerant to acetic acid (7,11). Some yeasts and molds are sensitive to acetic acid and include species ot Aspergillus, Penicillium, Rhizopus, and some strains of Saccharo-myces (7).
Acetic acid and its salts have shown variable success as antimicrobials in food applications. Acetic acid can increase poultry shelf life and decreases the heat resistance of Salmonella newport, Salmonella typhimurium, and Campylobacter jejuni in poultry scald tank water (12,13). The compound has been used as a spray sanitizer at 1.5 to 2.5% on meat carcasses and as a dip for beef or lamb (14).
Two-percent acetic acid affected large-scale reductions in the number of viable Escherichia coli 0157:H7 on beef after seven days at 5°C (15). Sodium acetate has been shown to increase the shelflife of meat and fish products and inhibits the molds, Aspergillus flavus,A. fumigatus,A. niger, A. glaucus, Penicillium expansum, and Mucorpusillus (7). Sodium diacetate inhibits mold growth in cheese spread and is an effective inhibitor of rope-forming bacteria (Bacillus subtilis) in baked goods (7). It is also inhibitory to L. monocytogenes, E. coli, Pseudomonas fluorescens, S. enter-itidis, and Shewanellaputrefaciens, but not S. aureus, Yersinia enterocolitica, P. fragi, Enterococcus faecalis, or Lactobacillus (7,16). Dehydroacetic acid has a high pKa of 5.27 and is therefore active at higher pH values. It is inhibitory to bacteria at 0.1 to 0.4% and fungi at 0.005 to 0.1% (7).
Acetic acid is used commercially in baked goods, cheeses, condiments and relishes, dairy product analogues, fats and oils, gravies and sauces, and meats. The sodium and calcium salts are used in breakfast cereals, candy, cheeses, fats and oils, gelatin, jams and jellies, meats, snack foods, sauces, and soup mixes (7). Sodium diacetate is used in baked goods, candy, cheese spreads, gravies, meats, sauces and soup mixes (7).
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