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Evaluation of the effects of gamma irradiation treatment on the compositional, textural, color, volatile profile, and microbiological quality of an artisanal hard-pressed cheese.

E. Raffrenato

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06-22-2020

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Abstract:

M43
Evaluation of the effects of gamma irradiation treatment on the compositional, textural, color, volatile profile, and microbiological quality of an artisanal hard-pressed cheese.
F. Nyamakwere1, G. Esposito2,1, K. Dzama1, P. Gouws1, T. Rapisarda3, G. Belvedere3, E. Raffrenato*2,1. 1Stellenbosch University Stellenbosch, South Africa, 2RUM&N Consulting Reggio Emilia, Italy, 3Consorzio per la Ricerca nel settore della Filiera Lattiero-Casearia e dell�agroalimentare Ragusa, Italy.

Irradiation treatment can be an effective way of reducing the incidence of food-borne pathogens on cheese, thus improving food safety. The objective of this study was to evaluate the efficacy of γ-irradiation against Listeria monocytogenes, Escherichia coli, coliforms and aerobic colony counts (ACC). At the same time effects on cheese composition, texture, color and odor properties were evaluated. The cheeses were manufactured at 4 farms using raw milk under artisanal processing conditions and aged for 60 dd. Samples were of either 250 or 500 g. The Cobalt-60 γ-irradiator was used at a maximum dose of 5.0 kGy, dose rate of 1 kGy/h and source strength was 150 kCi. Cheese samples both before and after treatment were analyzed by the “SMart Nose” system, by gas chromatography-mass spectrometry-olfactometry. Data were analyzed with the irradiation 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 irradiation treatment. All values were within the acceptable range for hard cheese. Dose and treatment length altered water-holding capacity and some enzymatic and bacterial activities affecting the mentioned parameters. All color parameters (lightness, redness, yellowness, chroma and hue angle) were decreased (P < 0.05) by the irradiation treatment. Hardness and chewiness values increased (P < 0.05), whereas, cohesiveness and springiness decreased (P < 0.05). The amounts of β-casein decreased (P < 0.05) after the treatment. SMart Nose on the principal component analysis and Odor Active Compounds showed differences (P < 0.05) between the non-irradiated and irradiated samples. The irradiation treatment caused a significant (P < 0.05) reduction of L. monocytogenes, E. coli, coliforms and ACC on the treated cheese samples. Results and the low cost suggest the potential use of the irradiation treatment as an affordable method to effectively control food pathogens for resource limited producers.

Keywords: volatile profile, ionizing radiation, microbial safety.

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