Inhibition of Listeria monocytogenes in hot dogs by surface application of freeze-dried bacteriocin-containing powders from lactic acid bacteria
15th International Conference on Food Processing & Technology
October 27-29, 2016 Rome, Italy

Gulhan Unlu, Barbara Nielsen and Claudia Ionita

University of Idaho, USA
Washington State University, USA
Clemson University, USA

Scientific Tracks Abstracts: J Food Process Technol

Abstract:

Six lactic acid bacteria (LAB) strains, Lactococcus lactis BFE 920, L. lactis subsp. lactis ATCC 11454, L. lactis subsp. cremoris ATCC 14365, Lactobacillus curvatus L442, Lact. curvatus LTH 1174, and Lact. bavaricus MN, were grown in cheddar cheese whey supplemented with complex nutrient sources. Cell-free culture supernatants were freeze-dried and the resulting bacteriocincontaining powders were applied on the surface of hot dogs that were inoculated (~ 4 log cfu/hot dog) with a five-strain Listeria monocytogenes cocktail. Hot dogs were vacuum sealed and stored at 4°C for 4 weeks. L. monocytogenes was enumerated, using both Tryptic Soy Agar (TSA) and Oxford Listeria Agar (OXA), on day 0 and at 1, 2, 3, and 4 weeks of the refrigerated storage. In hot dogs containing only the L. monocytogenes inoculum, L. monocytogenes counts increased from 4 log cfu/hot dog up to 7 log cfu/hot dog. All samples containing freeze-dried bacteriocin-containing powders exhibited significantly lowered (P < 0.05) L. monocytogenes populations on the surface of hot dogs throughout the 4-week study except for bavaricin MN powder. Bacterial counts on hot dogs packed without any powder were statistically equal on day 0 when enumerated on OXA. Freeze-dried bacteriocin-containing powders from L curvatus L442 and L. lactis subsp. cremoris ATCC 14365 decreased L. monocytogenes populations on the surface of hot dogs by greater than 2 log cfu/hot dog throughout the 4-week study. For the powdered bacteriocin preparations from L lactis BFE 920, L. lactis subsp. lactis ATCC 11454, and L. curvatus LTH 1174, L. monocytogenes populations were determined to be approximately 3-log cfu/hot dog after 4 weeks of storage.

Biography :

Gulhan Unlu is an Associate Professor within the School of Food Science at the University of Idaho and Washington State University. Her research interests include food microbiology, dairy microbiology, food biotechnology, microbial food safety, food bio-preservation, bioactive packaging of foods, functional foods, and bioconversion of agricultural and industrial waste into value-added products. She is an alumna (2012-2013) of The Fulbright US Scholar Program. She is an active member of the Institute of Food Technologists (IFT) and served as the Chair for the Biotechnology Division of the IFT (2014-2015). She serves on the Editorial Board of Probiotics and Antimicrobial Proteins.

Email: gulhan@uidaho.edu