Effects of g-irradiation on Listeria monocytogenes population, colour, texture and sensory properties of Feta cheese during cold storage

• Published in: Food microbiology 2009-04, Vol.26 (2), p.157-165
• Main Authors: Konteles, S, Sinanoglou, V J, Batrinou, A, Sflomos, K
• Format: Article
• Language: English
• Subjects: Listeria monocytogenes
• ISSN: 0740-0020
• DOI: 10.1016/j.fm.2008.10.006

Feta, a white brine cheese, was produced and contaminated with Listeria monocytogenes. Contamination occurred either at the beginning (pre-process contamination) or at the end of Feta manufacturing (post-process contamination). In the first case the milk was contaminated with 10 super(3)cfu/ml, and 2months later, in the final product, the L. monocytogenes population was approximately 10 super(5)cfu/g. In the second case, the brine (NaCl, 7% w/v), in which the Feta was packaged, was contaminated with 10 super(3)cfu/ml. Contaminated Feta samples were vacuum-packaged and exposed to irradiation doses of 1.0, 2.5 and 4.7kGy and stored at 4 super(o)C for a month. In the pre-process contaminated samples none of the irradiation doses eliminated L. monocytogenes; however the highest dose reduced the viable population to a level which is in compliance with EC regulations. In the post-process contamination, the 2.5kGy and 4.7kGy doses reduced L. monocytogenes counts below the detection limit. Irradiation had no effect on the texture of Feta. Irradiation at 4.7kGy increased Feta's redness and decreased its yellowness and lightness. Sensorial analyses showed that at the 4.7kGy dose, the aroma profile of Feta was temporarily affected, since it was restored after 30days of cold storage.