Effects of gamma-irradiation on Listeria monocytogenes population, colour, texture and sensory properties of Feta cheese during cold storage.
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(3) cfu/ml, and 2 months later, in the final product, the L. monocytogenes population was approximately 10(5) cfu/g. In the second case, the brine (NaCl, 7% w/v), in which the Feta was packaged, was contaminated with 10(3) cfu/ml. Contaminated Feta samples were vacuum-packaged and exposed to irradiation doses of 1.0, 2.5 and 4.7 kGy and stored at 4 degrees 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 2.5 kGy and 4.7 kGy doses reduced L. monocytogenes counts below the detection limit. Irradiation had no effect on the texture of Feta. Irradiation at 4.7 kGy increased Feta's redness and decreased its yellowness and lightness. Sensorial analyses showed that at the 4.7 kGy dose, the aroma profile of Feta was temporarily affected, since it was restored after 30 days of cold storage.
Konteles
Spyros
S
Laboratory of Food Microbiology, Department of Food Technology, Technological Educational Institution of Athens, Agiou Spyridonos St, 12210 Aegaleo, Greece. spycont@hotmail.com
Sinanoglou
Vassilia J
VJ
Batrinou
Anthimia
A
Sflomos
Konstantinos
K
D002611:Cheese / Q000382:microbiology* / Q000592:standards; D015169:Colony Count, Microbial; D003116:Color; D003257:Consumer Product Safety; D004307:Dose-Response Relationship, Radiation; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D005514:Food Irradiation / Q000379:methods*; D005519:Food Preservation / Q000379:methods*; D005720:Gamma Rays; D006801:Humans; D008089:Listeria monocytogenes / Q000254:growth & development / Q000528:radiation effects*; D013649:Taste; D013696:Temperature; D013997:Time Factors