Protein variations in Listeria monocytogenes exposed to sodium lactate, sodium diacetate, and their combination.

Most studies of the effect of adverse conditions on survival of Listeria monocytogenes have focused on stress caused by acid or sodium chloride. However, no information is available on resistance of this pathogen to stress caused by salts of organic acids. Sodium lactate and sodium diacetate are generally recognized as safe substances and are approved as ingredients for use in foods.

Factors affecting the antilisterial effects of nisin in milk.

The ability of Listeria monocytogenes to proliferate in milk and the antilisterial activities of nisin are well documented. Although milk fat was reported to reduce the antimicrobial activities of nisin, there is little information on the influence of milk fat on the antilisterial activities of nisin in refrigerated milk, and whether pasteurization and homogenization influence these activities. Fresh, pasteurized, and homogenized milk samples (0.

Automated measurements of antilisterial activities of lactate and diacetate in ready-to-eat meat.

Standard procedures to enumerate Listeria organisms rely on plating food samples on selective agar media. The procedures are labor-intensive, and because of the limited sensitivity, pre-enrichment step is required for the detection of low numbers of the pathogen. In the present study, an automated rapid optic procedure and the standard procedure were used to determine the behavior of the pathogen in ready-to-eat (RTE) meat and to test the effect of antilisterial agents.

Sensitivity of Six Strains of Listeria monocytogenes to Nisin.

The sensitivity of six strains of Listeria monocytogenes (serotype 1, 1a, 2, 4a, 4b, and a nonhemolytic strain) to nisin was compared at pH 5.0, 6.0, and 7.

Rapid Optical Measurements of Microbial Contamination in Raw Ground Beef and Effects of Citrate and Lactate.

The levels of microbial contamination in purchased pre-wrapped fresh ground beef samples were estimated by using the BioSys automated optical system for rapid detection of the presence of microorganisms. Additionally, the response of the system to the activity of antimicrobial agents in meat was evaluated after adding (separately) the sodium salts of lactic and citric acid to meat samples. Meat homogenates in peptone water were incubated at 30°C in broth containing the indicators bromcresol purple (pH) or resazurin (redox potential).

Survival of Listeria monocytogenes in Cottage Cheese.

Most studies on the behavior of Listeria monocytogenes in cheeses have focused on the soft, ripened types because of human listeriosis outbreaks linked to consumption of these foods, while observations in cottage cheese are limited and conflicting. Fresh market cottage cheese samples with and without sorbate, purchased in the United States and Canada, respectively, were contaminated with L. monocytogenes strain Scott A (10 CFU/g).

Antimicrobial Effects of Lactates: A Review.

Sodium lactate is used as humectant and flavor enhancer in meat and poultry products, and there is growing evidence of antimicrobial properties of the salt. Potassium and calcium lactate are equally effective in controlling growth of aerobes and anaerobes in meats, and antibotulinal and antilisterial activities of the lactate anion have been established. The specific action of lactate on the microbial cell is not well understood.

Relationship Between Water Activity, Salts of Lactic Acid, and Growth of Listeria monocytogenes in a Meat Model System.

The relationship between water activity (a), lactate, and growth of Listeria monocytogenes strain Scott A was studied in a meat model system consisting of cooked strained beef ranging in moisture content from 25 to 85% (wt/wt). Lactate (4%) depressed meat a, and differences between a values in control and lactate-treated samples at each moisture level increased progressively with decrease in moisture, from 0.003 (85% moisture) to 0.

Growth Suppression of Listeria monocytogenes by Lactates in Broth, Chicken, and Beef.

Sodium or potassium lactate is available commercially as a neutral aqueous solution (60%), approved for use as a flavoring agent in meat and poultry products. While recommended also for extending shelf life, little work on its antimicrobial effects has been published and none in relation to Listeria monocytogenes . Studies in tryptic soy broth showed that concentrations higher than 5% delayed growth of three strains of L.

Viability of Listeria monocytogenes Strain Brie-1 in the Avian Egg.

The viability of Listeria monocytogenes strain Brie-1 was studied in raw and heat-treated (121°C, 15 min) whole eggs, albumen, or yolks during storage at 5 and 20°C. Studies with raw eggs showed that the organism grew only in egg yolks, where initial numbers (10 cells/g) increased to 10 cells/g (generation times of 1.7 d and 2.

Survival of Listeria monocytogenes in Ground Beef or Liver During Storage at 4 and 25°C.

Survival and growth of three Listeria monocytogenes strains (Scott A, Brie-1, and ATCC 35152) were studied in ground beef or liver during storage from freshness to spoilage at 4 and 25°C. Cells were enumerated on Plate Count Agar, Trypticase Soy Agar, and selective media, including McBride Listeria Agar (MLA), Cyclohexanedione Nalidixic Acid Phenylethanol Agar (CNPA), LiCl Phenylethanol Moxalactam Agar (LPM), and LPM with potassium tellurite (LPMT). Aerobic natural microflora in the fresh uninoculated samples ranged from 10 to 10 CFU/g, and L.