Egg quality and salmonella spp. growth in shell eggs packaged in modified atmosphere packaging
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The effect of three types of modified atmosphere packaging (MAP) on the quality attributes and Salmonella spp. growth in oiled fresh USDA Grade AA shell eggs during storage was investigated. Shell eggs were subjected to one of four packaging treatments: (1) control - air; (2) 20% CO2/0.4% CO/79.6% N2; (3) 20% CO2/80% O2; and (4) 20% CO2/80% N2. Eggs were stored for up to 30 d, in a retail case at a temperature of 6 ± 1 C (refrigerated) or on shelves at 21 ± 1 C (abusive). Eggs were packed 8 to a tray with a tray considered as the experimental unit. Two trays per treatment per temperature per day were prepared in each trial with a total of three trials being conducted. Packages were opened and sampled on days (d) 1, 7, 14, 21, and 30 for determination of pH (yolk, albumen, whole egg), color (L*, a*, b*), TBARS, foam capacity and stability, Haugh units, and yolk index (YI). Data were analyzed by ANOVA in a 2 (temperature) x 4 (packaging treatment) x 5 (time-points) factorial design using programs in SAS. Where appropriate, means were separated by LSMeans. Whole egg pH was lower at both temperatures for the three MAP treatments (P < 0.05). Albumen pH for MAP treatments was significantly lower regardless of temperature as compared to the controls (P < 0.05). MAP treatment was effective at 6 C in maintaining lower yolk pH compared to control. A higher Haugh unit and yolk index throughout the storage at both temperatures was maintained by MAP treatment compared to the control treatment (P < 0.05). TBARS, and foam stability was similar for the MAP treatments and the control. Modified atmosphere packaging maintained higher foam capacity at both temperatures compared to control. Modified atmosphere packaging was effective in reducing egg deterioration and loss of functional quality during storage at refrigerated and abusive storage temperatures. For the effect of three types of MAP treatments on Salmonella spp. growth in shell eggs, sanitized shell eggs, inoculated with 40 ul cocktail of Salmonella Enteritidis phage 13 nalidixic acid resistant, S. Heidelburg/ 3347, S. Typhimurium ATCC 14028 strains and concentration of 1 x 104 cells were subjected to four packaging treatments. Eggs were packed 6 to a tray and sampled on days 1, 7, and 14. Data were analyzed by ANOVA in a 2 (temperature) x 4 (packaging treatment) x 3 (storage time) factorial design using programs in SAS. Where appropriate, means were separated by Duncan’s multiple range test and main effects were studied. MAP treatments were similar in their effect on Salmonella spp. growth at both the storage temperatures in trial 1 and 2. However, in trial 3, at refrigerated temperature, air packed eggs has the lower Salmonella count than the three MAPs. At abusive temperature, high-ox treatment had higher Salmonella count (P < 0.05).