This study determined the efficacy of actinidin and papain on reducing Listeria monocytogenes and three mixed strains of Escherichia coli O157:H7 populations on beef. The average reduction of E. coli O157:H7 was greater than that of L. monocytogenes and higher concentrations of either protease yielded greater reduction in bacterial populations. For instance, actinidin at 700 mg/ml significantly (p ≤ 0.05) reduced the population of L. monocytogenes by 1.49 log cfu/ml meat rinse after 3 h at 25 & 35 °C, and by 1.45 log cfu/ml rinse after 24 h at 5 °C, while the same actinidin concentration significantly reduced the populations of three mixed strains of E. coli O157:H7 by 1.81 log cfu/ml rinse after 3 h at 25 & 35 °C, and 1.94 log cfu/ml rinse after 24 h at 5 °C. These findings suggest that, in addition to improving the sensory attributes of beef, proteolytic enzymes can enhance meat safety when stored at suitable temperatures.
Hesham Taher Naas(12-2013)

Seventy five random samples were collected (25 raw milk, 50 local different made soft cheeses) from different supermarkets in Tripoli- Libya. The Objectives of this study were: (i)- to clear the incidence rate and count of coliforms as an indicator microorganisms for fecal contamination in raw milk and locally made soft cheese samples manufactured by traditional methods and (ii)- to make comparison between the most famous two conventional methods used for counting of such group of microorganisms. Coliforms were recovered from all the raw milk samples using the two methods (most probable number using liquid lauryl sulphate broth and sold plating method using violet red bile agar). The mean count for the former media was 28x106 while for the later one was 15x106 cfu/ml. For cheese samples (locally made Ricotta and Maasora), positive samples were 78% (39 samples) using MPN method, while 76% (38 samples) using sold plating media VRBA. The mean coliform count for positive samples using MPN was 18x107 cfu/g, while for VRBA plates the mean count for positive samples was 21x106 cfu/g. all counts were higher using MPN than VRBA for the same sample in both raw milk and cheese samples, although, clear difference in count between the two methods was recorded in cheese than that in raw milk, conditions that may affect the count in both raw milk and cheese were discussed. Factors that may limit
Hesham Taher Naas(1-2007)

Abstract Background: Whole muscle meat, meat products, and seafood contain different nutrients in adequate quantity providing a better environment for presence and replication of different microorganisms. There are underreported and inaccurate estimations of foodborne diseases due to the lack of effective surveillance systems in Libya. Aim: To determine the extent of microbiological contamination of whole muscle meat, meat products, and seafood. Methods: A total number of 731 samples of retail meat were collected from different stores in four cities in Libya. Samples were analyzed for aerobic plate count and subjected to microbiological enumeration and isolation techniques, followed by molecular identification by PCR and partial sequencing of 16S rDNA. Results: The results showed contamination of samples with enteric and spoilage bacteria. Fifteen genera of spoilage bacteria yielded 149 isolates which were detected and identified by PCR and partial sequencing of 16S rDNA as: Proteus spp., Provedencia spp., Raouttella ornithinolytical, Citrobacter spp., Enterobacter spp., Morganella morgi, Shewanella algea, Rhodobacter capsulatus, Listonella pelagia, Kluyvera spp., Pectobacterium spp., Brenneria spp., Klebsiella spp., Acintobacter radioresistens, and Pantoea spp. While for pathogenic bacteria, 143 isolates distributed among nine genera were identified by PCR and partial sequencing of 16S rDNA as: Bacillus spp., Escherichia spp., Shigella spp., Enterococci spp., Cronobacter spp., Staphylococci spp., Salmonella spp., Aeromonas spp., and Vibrio spp.. Many isolated bacteria are zoonotic bacteria with high importance for public health. Conclusion: Excessive handling and processing of meat and meat products seems to be one of the poorest microbiological qualities. These findings ought to be helpful in risk assessments and quality assurance of meat in order to improve food safety.
Hesham Taher Naas(9-2020)