No abstract

Summary Here, we evaluated the impact of bacterial growth stage on the effect of chitosan‐arginine (Ch‐arg) on Escherichia coli O157:H7 cell numbers and metabolic activity within contaminated beef juice held at room temperature. Using a lux‐marked metabolic reporter strain of E. coli O157:H7, the results showed that Ch‐arg was most bioactive against cells in the lag phase and exponential phase. In comparison, there was a reduced, although still significant, inhibitory effect of Ch‐arg on the viability and metabolic activity of E. coli O157 held in stationary phase. Ch‐arg reduced, but did not eliminate E. coli O157 growth in the meat juice over 48 h. Based on the evidence presented here and elsewhere, we conclude that Ch‐arg can limit the growth and activity of food spoilage bacteria; however, it cannot completely eliminate bacterial contaminants originally present. Ch‐arg should therefore be viewed as a potentially protective measure rather than a biocidal agent that completely eliminates the risk of pathogen transfer in the food chain.

This study was conducted in 2019 in Misurata, Libya. It aimed to compare the chemical and microbial characteristics of samples of (Rub Al-Tamr) produced by traditional and modern methods and calculate their energy content. Traditional (Deglah Nour, Khadrawi, Tasfart and Bekrari) and modern (Dibs Al-Tamr) Rub Al-Tamr samples were collected from the Alwaha Factory (Benghazi, Libya). The most important chemical results showed that none of the traditionally manufactured samples of Rub Al-Tamr conformed to Libyan Standard No. 44 of 1992 in average percentage of moisture, total sugars and total soluble solids but matched the standard in average ash content. The Deglah Nour sample recorded a high content of iron (7.55 ppm). However, all date syrup samples were free of heavy metals. The microbial test results showed that the Rub Al-Tamr samples were free of bacterial growth except for the sample of Deglah Nour, but most of the samples were contaminated with yeasts and moulds. The results showed that Dibs Al-Tamr contained the highest energy ratio and the Khadrawi sample was ranked second. The important recommendations of this study were to improve Libyan standard specifications for date syrup and to increase awareness programmes regarding the tools used in extracting date syrup. ‫األحمر‬ ‫القادر‬ ‫عبد‬ ‫ربيعة‬ ‫للا،‬ ‫عبد‬ ‫صالح‬ ‫محمد‬ ‫هاجر‬ ‫و‬ ‫دغمان‬ ‫صالح‬ ‫منى‬ (. 2020 .) ‫والحديثة‬ ‫التقليدية‬ ‫بالطريقة‬ ‫املصنع‬ ‫التمر‬ ‫لرب‬ ‫الطاقة‬ ‫ومحتوى‬ ‫وامليكروبية‬ ‫الكيميائية‬ ‫الخواص‬. ‫فرع‬ ‫فيصل،‬ ‫امللك‬ ‫لجامعة‬ ‫العلمية‬ ‫املجلة‬ ‫والتطبيقية،‬ ‫األساسية‬ ‫العلوم‬ (‫املجلد‬ 21 (‫العدد‬ ،) 2)

Escherichia coliO157:H7 is a potentially lethal pathogen which has been responsible for several outbreaks of milk-borne illness in recent years. The objective of this study was to evaluate the survival and metabolic activity (indexed by bioluminescence) of a chromosomallylux-marked strain ofEsch. coliO157:H7 in raw, pasteurized and microfiltered pasteurized milk at 4 and 20°C for up to 14 d. Results showed that the population ofEsch. coliO157:H7 and its metabolic activity decreased in all samples during storage at 4°C, with no significant differences in numbers observed between the different milk types; but metabolic activity was significantly higher (P<0·05) in the microfiltered pasteurized milk than that in raw milk. At 20°C,Esch. coliO157:H7 counts and cell activity peaked at day 2, and then declined progressively. At 20°C, survival and metabolic activity were significantly lower in raw milk compared with pasteurized milk. We conclude that storage temperature is more important in regulating the survival ofEsch. coliO157 in contaminated milk than its origin/pre-treatment conditions.

The aim of this study was to evaluate the bacteriological quality and safety of fresh white cheese sold in Tripoli, Libya. The study lasted for approximately 7 months (November 2011-May 2012), during this period 87 fresh white cheese samples were collected from seven different areas (4 to 5 factories from each area with the rate of 3 duplicates). The samples were tested for temperature at receiving, pH and acidity, total aerobic counts, total coliform counts and the detection of incidence of some pathogenic bacteria including: Escherichia coli, Escherichia coli O157:H7, Staphylococous aureus, Salmonella spp., Aeromonas hydrophila and Listeria monocytogenes. Results indicated that the average temperature, % acidity, and pH of the tested samples were (15.80°C ± 5.8, 0.21 ± 0.02% and 5.81 ± 0.06) respectively. Data indicated that 70.1% of the samples exceeded the Libyan standard for white cheese No. 366 in respect to temperature, while pH of all samples was within the limits of such standard. On the other hand, means of total aerobic counts, total coliform counts, and the numbers of Staphyloccoccus aureus were (38 × 10 7 , 74 × 10 5 , 35 × 10 4 and 53 × 10 3 cfu/g) respectively of the study. b ia l & Bioc h e m ic a l Te chno lo g y