title: Inhibitory effect of combinations of caprylic acid and nisin on Listeria monocytogenes in queso fresco.
abstract: Queso fresco (QF), a fresh Hispanic cheese has been linked to outbreaks and recalls caused by Listeria contamination. The use antimicrobial treatments may be a potential solution. The goal of this research was to test the addition of nisin (N), caprylic acid (CA) and trans-cinnamaldehyde (CN) as anti-listerial ingredients in QF. QF batches were inoculated with approx. 10(4) CFU/g of 5- or 6-strain mixtures of Listeria monocytogenes and treated with antimicrobials. Samples were stored at 4 °C for three weeks and Listeria counts were determined by plating on PALCAM agar. The impact on the QF's natural indicator microorganisms was also assessed during refrigerated storage. All N and CA combinations (≥0.4 g/kg each) were effective against L. monocytogenes and reduced the final counts by at least 3 log CFU/g after 20 days of storage compared to controls. The levels of most strain mixtures were reduced immediately after treatment and their numbers remained below 10(3) CFU/g during storage. CN (1.2 g/kg) was bacteriostatic against L. monocytogenes, but it did not reduce initial counts. The addition of CN to the combination of N and CA did not enhance their antimicrobial effect. Results indicated that combinations of N and CA could control L. monocytogenes in QF with little impact on the natural flora of the cheese, providing a solution to control post processing L. monocytogenes contamination of QF.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, 1354 Eckles Ave., St. Paul, MN 55108, United States.
authors.forename: Camila
authors.initials: C
authors.lastname: Gadotti
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, 1354 Eckles Ave., St. Paul, MN 55108, United States.
authors.forename: Laura
authors.initials: L
authors.lastname: Nelson
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, 1354 Eckles Ave., St. Paul, MN 55108, United States. Electronic address: fdiez@umn.edu.
authors.forename: Francisco
authors.initials: F
authors.lastname: Diez-Gonzalez
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002210:Caprylates / Q000494:pharmacology*; D002611:Cheese / Q000382:microbiology*; D005519:Food Preservation / Q000379:methods*; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D009561:Nisin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D002210:Caprylates; D009561:Nisin; C031492:octanoic acid
keywords: Caprylic acid; GRAS; Hispanic cheese; Listeria monocytogenes; Nisin; Queso fresco; trans-Cinnamaldehyde