Evaluation of the Bacteriological quality of two types ‎of salad prepared at the Libyan Airlines Catering ‎Center in Tripoli, Libya

Abstract

The aim of this study was to evaluate the bacteriological quality of two types of salads prepared at Libyan airlines catering center near Tripoli International Airport /Tripoli, Libya. The study lasted for 10 months starting from January until October, 2010. During this period 221 salad samples (132 for the economy class and 89 samples for business and flight crew class) were collected. All samples were subjected to periodical bacteriological analysis which included determination of Total Plate Count (TPC), Total Coliforms (TCF) count, in addition to detection and enumeration of some pathogenic bacteria: Escherichia coli, Staphylococcus aureus, Salmonella spp., Vibrio parahaemolyticus, Bacillus cereus and Listeria spp. using two methods of detection: conventional method vs. compact dry method. The results of the study have shown that the mean of initial TPC for the first type of salad were 11.38 x10³ cfu/g using the conventional method of enumeration and 54.17x10² cfu/g using the compact dry method, while the means of TCF count were 54.07x10² and 14.90 x10² cfu/g using the first and the second method respectively. On the other hand the initial TPC means for the second type of salad were 64.00x10² cfu/g using the first method and 81.30 x10² cfu/g using the second method. The TCF count means were 15.40 x10³ and 78.60 x10² cfu/g using both methods respectively. Even though, there was no significant difference between the two types of salads in respect of TPC and TCF counts, data indicated that the conventional method appears to have a relatively better support for total microbial growth vs. the compact method. A gradual decline in TPC and TCF counts were observed throughout the period of the study and reached minimum values at the end of the last month. The reduction percentages of TPC in the economy class salad were 14.24% and 61.69% at the 2^nd and 3^rd months vs. 90.77% vs 99.02% reduction at the end of the last month of the study using the conventional method of enumeration. Relatively similar pattern was observed for business and flight crew class salad. The results have shown that the presence of pathogenic bacteria was different depending on the type of salad and the detection method applied. S. aureus was the most predominant in the economy class salad representing 17.4% of the samples using the conventional method and 14.4% using the compact dry method. As for E. coli it was detected in 7.6% and 9.8% of the samples using the conventional method and the compact dry method respectively.  Salmonella spp. was present in 3.4% and 3.8% of the samples using both methods of detection respectively. On the other hand, the presence of these pathogens was reversed in the business and flight crew class salad, since E. coli recorded the highest percentage (14.6% and 16.9 %) followed by S. aureus (13.5% and 11.2%), and then Salmonella spp. (6.7% and 6.70%) using the conventional method and the compact dry method respectively. V. parahaemolyticus which was detected using the compact dry method only recorded the least percentage (4.9%). As for B. cereus and Listeria spp. they were not detected in either type of salad. Finally, the data indicated that the significance decrease in bacteriological counts at the end of the sixth and the seventh months of the study, was coincided with the application of the (HACCP) system for the first time at the catering center.