Dairy Foods 1

摘要

Irradiation treatment can be an effective way of reducing the incidenceof food-borne pathogens on cheese, thus improving food safety. The objectiveof this study was to evaluate the efficacy of γ-irradiation againstListeria monocytogenes, Escherichia coli, coliforms and aerobic colonycounts (ACC). At the same time effects on cheese composition, texture,color and odor properties were evaluated. The cheeses were manufacturedat 4 farms using raw milk under artisanal processing conditions and agedfor 60 dd. Samples were of either 250 or 500 g. The Cobalt-60 γ-irradiatorwas used at a maximum dose of 5.0 kGy, dose rate of 1 kGy/hand source strength was 150 kCi. Cheese samples both before and aftertreatment were analyzed by the “SMart Nose” system, by gas chromatography-mass spectrometry-olfactometry. Data were analyzed with theirradiation treatment and sample weight as the main fixed factors. Moisture,pH, total nitrogen, fat in dry matter, water activity were reduced (P< 0.05) and salt and salt in moisture increased (P < 0.05) after the irradiationtreatment. All values were within the acceptable range for hardcheese. Dose and treatment length altered water-holding capacity andsome enzymatic and bacterial activities affecting the mentioned parameters.All color parameters (lightness, redness, yellowness, chroma and hueangle) were decreased (P < 0.05) by the irradiation treatment. Hardnessand chewiness values increased (P < 0.05), whereas, cohesiveness andspringiness decreased (P < 0.05). The amounts of β-casein decreased (P <0.05) after the treatment. SMart Nose on the principal component analysisand Odor Active Compounds showed differences (P < 0.05) between thenon-irradiated and irradiated samples. The irradiation treatment caused asignificant (P < 0.05) reduction of L. monocytogenes, E. coli, coliformsand ACC on the treated cheese samples. Results and the low cost suggestthe potential use of the irradiation treatment as an affordable methodto effectively control food pathogens for resource limited producers.