الفهرس 
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Abstract
The present investigation was designed to determine the quality of some ready-to-eat meat products. A total of 120 samples included 30 each of chilled ready-to-eat smoked beef, rose beef, roast beef, and beef bacon, were randomly collected from different supermarkets in Assiut city, Egypt, and directly transported to the laboratory where it were subjected to sensory, chemical and bacteriological examinations.
The results of sensory evaluation showed that 24 (80%) and 16 (53.34%) of smoked beef and roast beef samples were recorded as like extremely (score 9), while 23 (76.66%) and 16 (53.34%) of rose beef and beef bacon samples were recorded as like very much (score 8), respectively. So, all the examined samples were accepted organoleptically.
The mean pH value of smoked beef samples was 6.36 ± 0.08, while in rose beef samples was 6.75 ± 0.09. In roast beef samples, the mean pH value was 6.14 ± 0.02 and in beef bacon was 6.62 ± 0.03.The mean pH values were varied significantly (P<0.05) between smoked beef, rose beef and roast beef samples as well as between smoked beef, roast beef and beef bacon samples. However, no significant (P>0.05) difference was obtained between the mean values of rose beef and beef bacon samples.
Regarding, the moisture content of smoked beef, rose beef, roast beef and beef bacon, the mean values were 70.49 ± 0.20, 73.27 ± 0.45, 70.36 ± 0.08 and 64.33 ± 0.63, respectively. The statistical analysis revealed a significant (P<0.05) difference between the smoked beef, rose beef and beef bacon mean values and between rose beef, roast beef and beef bacon mean values. However, no significant (P>0.05) difference was found between the smoked beef and roast beef mean values.
As for, protein content the mean values of the examined samples were 22.04 ± 0.20, 18.45 ± 0.55, 21.99 ± 0.14 and 24.58 ± 0.53, respectively. A significant (P<0.05) difference in the protein content was recorded between the mean values of smoked beef, rose beef and beef bacon samples with the higher value was found in case of beef bacon. As well, the mean values of rose beef, roast beef and beef bacon samples were also significantly (P<0.05) differ. On the other hand the mean values of smoked beef and roast beef were not significantly (P>0.05) different.
Concerning, fat content, the mean values were 1.99 ± 0.14 , 2.28 ± 0.22, 1.55 ± 0.10, and 6.22 ± 0.40 for smoked beef , rose beef, roast beef and beef bacon samples, respectively. The mean value of beef bacon was significantly (P<0.05) higher than either of rose beef, smoked beef and roast beef mean values. Likewise rose beef mean value was significantly (P<0.05) higher than that of roast beef. On the other hand no significant (P>0.05) difference was recorded between smoked beef and rose beef mean values or between smoked beef and roast beef mean values.
Regarding, ash content, the mean values of the previously examined samples were 3.45 ± 0.05, 3.70 ± 0.09, 3.49 ± 0.05 and 2.60 ± 0.12, respectively. No significant (P>0.05) difference was recorded between the mean values of smoked beef, rose beef and roast beef samples. However, the mean value of beef bacon samples was significantly (P<0.05) differ from those of the other inspected products.
The mean values of total carbohydrate percent was 2.01 ± 0.11 in smoked beef samples, while in rose beef samples was 2.30 ± 0.10. In roast beef samples, the mean value of 2.61 ± 0.07 and in beef bacon samples the mean value of 2.26 ± 0.11.A statistical significant (P<0.05) difference was recorded between the roast beef mean value and either of smoked beef, rose beef and beef bacon mean values , while no significant (P>0.05) difference was detected between the mean values of smoked beef, rose beef and beef bacon samples.
The mean gross energy values (Kcal/100gm) were 114 ± 1.22, 104 ± 2.18, 112 ± 0.71 and 163 ± 4.35 for smoked beef, rose beef, roast beef and beef bacon samples, respectively. The mean value of smoked beef, rose beef and beef bacon samples and those of rose beef, roast beef and beef bacon samples were significantly (P<0.05) differ, while those of smoked beef and roast beef were not significantly (P>0.05) differ.
The mean values of cholesterol content (mg/100gm) of the examined smoked beef, rose beef, roast beef and beef bacon samples were 62.19 ± 2.21, 66.94 ± 1.77, 73.76 ± 2.35 and 65.41 ± 2.47, respectively. The mean value of roast beef was significantly (P<0.05) differ from those of smoked beef, rose beef and beef bacon. Meanwhile, the mean values of smoked beef, rose beef and beef bacon was not significantly (P>0.05) differ from each other.
Aerobic bacteria were existed in all the examined samples. The mean values of aerobic plate count (log cfu/g) of the examined samples were 8.42 ± 0.04, 8.41± 0.07, 8.59 ± 0.02 and 8.44 ± 0.02, for smoked beef, rose beef, roast beef and beef bacon samples, respectively. The mean values of smoked beef, rose beef and beef bacon samples were not significantly (P>0.05) differ for their APC. While that of roast beef was significantly (P<0.05) differ from each of smoked beef, rose beef and beef bacon mean values.
Enterococci could be detected in the examinedready-to-eat meat products where the mean values in smoked beef, rose beef, roast beef and beef bacon samples were 7.98 ± 0.07, 7.82 ± 0.10, 8.11 ± 0.05 and 8.04 ± 0.04, respectively.A significant (P<0.05) difference was recorded between rose beef and each of roast beef and beef bacon mean values. However, the mean values of smoked beef, roast beef and beef bacon were not differ significantly (P>0.05). Likewise a non-significant (P>0.05) difference was found concerning the mean values of smoked beef and rose beef samples.
The incidence of Listeriaspecies was 20, 20, 6.67 and 30% in smoked beef, rose beef, roast beef and beef bacon samples, respectively. L. monocytogenes was detected in 3.33, 3.33, 3.33 and 10%, and L. ivanovii in 10, 13.33, 3.33 and 16.67% of the previously mentioned samples, respectively. L. welshimeri was detected in 6.67% of smoked beef, while L. grayi in 3.33% of rose beef and L. innocua in 3.33% of beef bacon samples only.
Yersiniaspecies were detected in 43.33, 20, 26.67, and 30% of smoked beef, rose beef, roast beef and beef bacon samples, respectively. Y. entercolotica was detected at an incidence rate of 10, 10, 13.33 and 16.67%. Meanwhile and Y. Kristensenii was detected at a rate of 16.67, 6.67, 3.33 and 3.33%, and Y. pseudotuberculosis at a rate of 10, 3.33, 3.33 and 6.67% in the previously mentioned samples, respectively. Y. intermedia was isolated only from smoked beef at a percentage of 6.67%, while Y. freedriksenii was isolated from 3.33% of beef bacon samples only.
The incidence of E. coli was 23.33, 26.67, 13.33 and 33.33% for smoked beef, rose beef, roast beef and beef bacon samples, respectively. E. coli O111:H2 was isolated from the previous samples at a rate of 10, 6.67, 3.33 and 3.33%, respectively, meanwhile, E. coli O55:H7 was detected at a rate of 13.33% in each of smoked beef and beef bacon samples. E. coli O91:H21 was recorded in 6.67% and E. coli O125:H21 in 3.33% of rose beef samples. However, E. coli O26:H11 was found in 10, 10 and 6.67% of rose beef, roast beef and beef bacon samples, respectively.
E. coli O157:H7 and E. coli O44:H18 were detected only in beef bacon samples at a rate of 6.67 and 3.33%, respectively.
By PCR 2 of the 3 L. monocytogenes isolates were found to have the 3 virulence genes iap, hylA and act A, while the 3rd isolate was found to have only two of these genes ”iap and hylA”.
Of the 7 isolates of Y. entercolotica, 5 were found to have both of the virulence genes inv and ystA genes, and 2 were found to have only inv gene.
Concerning E. coli isolates, E. coli O26, O111 and O157 were found positive for stx1, stx2 and eaeA virulence genes, while E. coli O55 and O91 were found only positive for stx1 and stx2 genes. E. coli O44 isolates were found positive only for stx2 gene and E. coli O125 positive only for stx1 gene.
The public health significance of the recovered pathogenic microorganisms as well as the recommended measures to minimize the risk associated with ready-to-eat meat products were discussed.