Abstract This study aimed to evaluate the antibacterial activity of flavonoids extracted from two Libyan brown algae namely Cystoseira compressa and Padina pavonica using microwave-assisted extraction method against pathogenic bacteria isolated from meat, meat products, milk and dairy products (Staphylococcus aureus subsp. aureus (5 isolates), Bacillus cereus (3 isolates), Bacillus pumilus (1 isolate), Salmonella enterica subsp. enteric (4 isolates) and Enterohaemorrhagic Escherichia coli O157 (EHEC O157) (4 isolates)). All of these isolates were muti-drug resistant with high MAR index. The results showed that C. compressa extract exhibited better and stronger antibacterial activities against the seventeen tested isolates with inhibition zones diameter ranged from 14 - 22 mm compared to P. pavonica extract which showed positive effect against 9 isolates with low inhibition zone ranged from 11 - 16.5 mm. Flavonoids extracted from C. compressa also displayed the best spectrum of bactericidal effect with a ratio MBC/MIC ≤ 4 obtained on all susceptible tested bacterial strains. Flavonoids and proanthocyanidins significantly contributed to the antibacterial properties. The mode of action of these active extracts is under investigation.
Hesham Taher Naas(1-2017)

The objective of this study was to determine the antimicrobial activity of proteolytic, meat-tenderizing enzymes (papain and bromelain) against E. coli and L. monocytogenes at three different temperatures (5, 25 and 35°C). Two overnight cultures of E. coli JM109 and L. monocytogenes were separately suspended in 1% peptone water and exposed to a proteolytic enzyme (papain or bromelain) at three different temperatures. Bromelain concentrations (4 mg/ml) and (1 mg/ml) tested at 25°C against E. coli and L. monocytogenes, respectively, were the most effective concentrations tested reducing populations by 3.37 and 5.7 log CFU/ml after 48 h, respectively. Papain levels of (0.0625 mg/ml) and (0.5 mg/ml) were the most effective concentration tested at 25°C against E. coli and L. monocytogenes, respectively, reducing populations by 4.94 and 6.58log CFU/ml after 48h, respectively. Interestingly, the lower papain concentration tested (0.0625 mg/ml) was more effective than the higher concentration (0.5 mg/ml) against E. coli at all three temperatures. As expected, the temperature was directly related to enzyme efficacy against both E. coli and L. monocytogenes.
Hesham Taher Naas(1-2013)

The objective of this study was to evaluate the effect of nisin in combination with different types of packaging on the survival of Listeria monocytogenes in ready-to-eat low-fat turkey bologna. Bologna was inoculated with L. monocytogenes exposed to 1 of 6 treatments: 3 packaging treatments (100% CO2, air, vacuum), each with and without nisin. Bologna was refrigerated and sampled 9 times over 42 d. Nisin reduced initial L. monocytogenes populations by 1.5 to 2 log cycles and 100% CO2 packaging prevented outgrowth throughout 42 d of storage, whereas non-CO2 packaging displayed a 2-log increase in population during storage. Nisin (500 IU/mL) combined with 100% CO2 was effective in reducing Listeria and preventing outgrowth on bologna over 42 d of refrigerated storage.
Hesham Taher Naas(3-2013)