INFLUENCE OF SORBIC ACID ON THE GROWTH OF CERTAIN SPECIES OF BACTERIA, YEASTS, AND FILAMENTOUS FUNGI

4: Final Report on the Safety Assessment of Sorbic Acid and Potassium Sorbate

Sorbic acid is a straight-chain monocarboxylic acid used in cosmetic formulations as a preservative at concentrations up to 1.0%.

Sorbic acid and potassium sorbate were practically nontoxic to rats and mice in acute oral toxicity studies. In subchronic studies no significant adverse effects were observed in rats, mice, or dogs when 10% sorbic acid was included in the diet.

Sorbic acid and potassium sorbate at concentrations up to 10% were practically nonirritating to the rabbit eye. Both ingredients at concentrations up to 10% were at most only slightly irritating.

Sorbic acid and potassium sorbate have been tested for mutagenic effects using the Ames test, genetic recombination tests, reversion assays, rec assays, tests for chromosomal aberrations, sister chromatid exchanges, and gene mutations. Results have been both positive and negative.

Potassium sorbate at 0.1% in the diet or 0.3% in drinking water of rats for up to 100 weeks produced no neoplasms. In other chronic studies, no carcinogenic effect was demonstrated by sorbic acid in rats or mice fed diets containing up to 10% sorbic acid.

No teratogenic effects have been observed in pregnant mice and rats administered potassium sorbate.

In three repeat insult patch tests, sorbic acid had overall sensitization rates of 0, 0.33, and 0.8%. All of the subjects sensitized were inducted with 20% sorbic acid and challenged with 5% sorbic acid. Formulations containing up to 0.5% sorbic acid and or potassium sorbate were not significant primary or cumulative irritants and not sensitizers at this test concentration. A formulation containing 0.01% sorbic acid was not a photosensitizer.

On the basis of the available data, it is concluded that sorbic acid and potassium sorbate are safe as cosmetic ingredients in the present practices of use and concentration.

Sorbic Hydroxamic Acid, an Antifungal Agent Effective over a Wide pH Range

Sorbic hydroxamic acid was prepared from sorbic acid by esterification and treatment with hydroxylamine (mp 133 to 135 C, pK(a) 8.8). Its ultraviolet spectrum in acid solution had a single absorption maximum at 262 mmu; in alkaline solution the maximal absorption shifted to 255 mmu and significant absorption appeared at 280 to 300 mmu. At concentrations of 0.1% (w/v), sorbic hydroxamic acid prevented the growth of Aspergillus niger, Penicillium notatum, Botrytis cinerea, Cladosporium herbarum, and a Rhizopus species in grape juice over the pH range 3.6 to 9.2, although sorbic acid was not effective at pH 5.7 and above.

Modelling bacterial spoilage in cold-filled ready to drink beverages by Acinetobacter calcoaceticus and Gluconobacter oxydans

AIMS

Mathematical models were created which predict the growth of spoilage bacteria in response to various preservation systems.

METHODS AND RESULTS

A Box-Behnken design included five variables: pH (2.8, 3.3, 3.8), titratable acidity (0.20%, 0.40%, 0.60%), sugar (8.0, 12.0, 16.0 * Brix), sodium benzoate concentration (100, 225, 350 ppm), and potassium sorbate concentration (100, 225, 350 ppm). Duplicate samples were inoculated with a bacterial cocktail (100 microl 50 ml(-1)) consisting of equal proportions of Acinetobacter calcoaceticus and Gluconobacter oxydans (5 x 10(5) cfu ml(-1) each). Bacteria from the inoculated samples were enumerated on malt extract agar at zero, one, two, four, six, and eight weeks.

CONCLUSION

The pH, titratable acidity, sugar content, sodium benzoate, and potassium sorbate levels were all significant factors in predicting the growth of spoilage bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

This beverage spoilage model can be used to predict microbial stability in new beverage product development and potentially reduce the cost and time involved in microbial challenge testing.

Effect of Benzoic Acid on Growth Yield of Yeasts Differing in Their Resistance to Preservatives

Yeasts grown in the presence of benzoic acid tolerated 40 to 100% higher benzoic acid concentrations than did those grown in the absence of weak-acid-type preservatives. They also accumulated less benzoate in the presence of glucose. In chemostat cultures, benzoic acid reduced growth yield and the rate of cell production but increased specific fermentation rates. Benzoate contents were lower than those required for equilibrium when cells were impermeable to benzoate anion. Intracellular pHs were maintained near neutrality. Between species, stimulation of fermentation was inversely related to preservation resistance but was unrelated to the maximum rate of fermentation. The results show that a major effect of benzoic acid on yeasts in the presence of an energy source is the energy requirement for the reduction in cytoplasmic benzoate concentration and maintenance of pH. This energy source is unavailable for growth, resulting in lower growth yields and rates. Resistant species may be less permeable to undissociated benzoic acid.

Food additives and plant components control growth and aflatoxin production by toxigenic aspergilli: a review

Growth and aflatoxin production by toxigenic aspergilli are partially or completely inhibited by the undissociated form of acetic, benzoic, citric, lactic, propionic and sorbic acids. Salts such as sodium chloride, potassium chloride and sodium nitrate, at low concentrations, can enhance aflatoxin production. At higher concentrations they become inhibitory, but marked inhibition requires amounts of the salts greater than are commonly used in foods. Phenolic antioxidants, sometimes added to foods to prevent oxidative deterioration, also are inhibitory to toxigenic aspergilli. Other inhibitory agents include certain insecticides, methylxanthines (caffeine and theophyllin), and components of some herbs, spices and other plants.

Potential for Development of Tolerance by Penicillium digitatum and Penicillium italicum after Repeated Exposure to Potassium Sorbate

Two strains of Penicillium digitatum and one strain of Penicillium italicum were exposed to various levels of sorbic acid and potassium sorbate, and the MICs were determined. Selected strains of the molds were then repeatedly exposed to subinhibitory levels of the compounds to determine whether increased tolerance might develop. The MIC of sorbic acid (pH 4.75) to P. digitatum was between 0.02 and 0.025%. The MIC of sorbate (pH 5.5) to two strains of P. digitatum and P. italicum was found to be between 0.06 and 0.08%. Increasing levels of sorbate resulted in increasing growth suppression of the molds. Populations of P. digitatum were tested for increased tolerance to sorbic acid, and none was found. Individual molds that started from the same parent colony were examined for increased tolerance to potassium sorbate. Two P. digitatum strains developed no observable increased tolerance, but P. italicum developed a slight increase in tolerance to sorbate. When spores of P. italicum and P. digitatum were exposed to higher levels of sorbate for prolonged times, the fungicidal or fungistatic activity of the inhibitor was dependent upon pH, length of exposure time, level of sorbate, and the mold strain.

Nitrite, nitrite alternatives, and the control of Clostridium botulinum in cured meats

Historically, nitrite has been a component of meat-curing additives for several centuries. In recent years the safety of nitrite as an additive in cured meats has been questioned mainly because of the possible formation of carcinogenic nitrosamines. Nitrite has many important functions in meat curing including its role in color development, flavor, antioxidant properties, and antimicrobial activity. The inhibition of Clostridium botulinum growth and toxin production is an especially important antimicrobial property of nitrite. This review discusses the effects of processing, curing ingredients (especially nitrite), and storage of cured meats in relation to the control of C. botulinum. If nitrite is eliminated from cured meats or the level of usage decreased, then alternatives for the antibotulinal function of nitrite need to be considered. Several potential alternatives including sorbates, parabens, and biological acidulants are discussed.

[The activity of sorbic acid against mycotoxin forming microorganisms (author's transl)]

Potassium sorbate at a concentration of 200-400 ppm inhibits mycotoxin forming Aspergillus versicolor at a pH of 5.7-5.9 in culture media and fermented sausages.

Antimicrobial activity of some N-substituted amides of long-chain fatty acids

Seventy-three N,N-disubstituted amides of long-chain, principally C(18), fatty acids were screened for antimicrobial activity against bacteria, yeasts, and molds. Amides containing an epoxy group exhibit a broad spectrum of antimicrobial activity which is further enhanced by unsaturation. Mono-unsaturation alone does not contribute a broad level of activity to the N,N-disubstituted amides of the C(18) fatty acids.

Bloater Formation by Gas-forming Lactic Acid Bacteria in Cucumber Fermentations

The formation of “bloaters” (hollow stock) in cucumbers brined for salt-stock purposes at 5 to 10% salt has been associated with gaseous fermentation caused chiefly by yeasts. Recently, serious early bloater damage, not attributable to yeasts, has been observed in commercial-scale experiments on control of bloaters in overnight dill pickles brined in 50-gal barrels at 3.0 to 4.5% salt. Growth of fermentative species of yeasts was effectively controlled by the addition of 0.025, 0.05, and 0.1% sorbic acid or its sodium salt. In contrast to this, the fermenting brines showed extremely high populations of acid-forming bacteria, identified as Lactobacillus plantarum, L. brevis , and Pediococcus cerevisiae . The gas-forming species (i.e., L. brevis ) constituted a high proportion of the total populations. Representative isolates from 36 barrels of overnight dill pickles were tested for their ability to produce bloaters in 1-quart jars of pasteurized cucumbers equilibrated at 4 to 5% salt, 0.25% lactic acid, and p H 4.0. Bloaters, identical with those made by yeast cultures, were produced in all jars inoculated with L. brevis . No bloaters were produced by L. plantarum and P. cerevisiae . These results suggest that the control of bloater damage in cucumber fermentations, particularly at low salt concentrations, may necessitate inhibition of gas-forming lactic acid bacteria.