In this study, the interaction of a bioluminescence-labeled Escherichia coli strain with growing spinach plants was assessed. Through bioluminescence profiles, the direct visualization of E. coli growing around the roots of developing seedlings was accomplished. Subsequent in situ glucuronidase (GUS) staining of seedlings confirmed that E. coli had become internalized within root tissue and, to a limited extent, within hypocotyls. When inoculated seeds were sown in soil microcosms and cultivated for 42 days, E. coli was recovered from the external surfaces of spinach roots and leaves as well as from surface-sterilized roots. When 20-day-old spinach seedlings (from uninoculated seeds) were transferred to soil inoculated with E. coli, the bacterium became established on the plant surface, but internalization into the inner root tissue was restricted. However, for seedlings transferred to a hydroponic system containing 10(2) or 10(3) CFU of E. coli per ml of the circulating nutrient solution, the bacterium was recovered from surface-sterilized roots, indicating that it had been internalized. Differences between E. coli interactions in the soil and those in the hydroponic system may be attributed to greater accessibility of the roots in the latter model. Alternatively, the presence of a competitive microflora in soil may have restricted root colonization by E. coli. The implications of this study's findings with regard to the microbiological safety of minimally processed vegetables are discussed.

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Ethanolic extracts of tarragon (Artemisia dracunculus), rosemary (Rosemarinus officinalis L) and thyme (Thymus vulgaris L.) and the essential oil of oregano (Origanum vulgare L.) were tested against many fungi including A.niger, A.flavus, Penicillium spp., Rhizopus spp. and fusarium spp. Oregano essential oil showed a very strong antifungal activity against Fuazarium spp. (MIC: 0.8 mg/ml), A.niger (MIC: <1 mg/ml) and Penicillium spp. (MIC: 4.5 mg/ml) whereas other fungi showed more resistant. The results showed that Rhizopus spp. was the most sensitive fungus to the plant extracts whereas rosemary was the most effective plant. Application of essential oils or ethanolic rosemary extract with different concentrations (100, 500, 1000, 1500, 2000 ppm) and refrigeration storage (at either 5 or 25°C) for postharvest spoilage control of tomatoes for 4 weeks showed that the combination of two treatments (refrigeration with either oregano essential oil or rosemary extract) was more effective to keep quality of tomatoes.

The efficacy of seed decontamination to enhance the safety of salad vegetables and herbs was evaluated. Seeds (celery, coriander, lettuce, spinach and watercress) were inoculated (at a level of 3-5 log cfu g −1 ) with either Escherichia coli P36 or Listeria monocytogenes NCTC 7973 and decontaminated with ozone gas, acidified sodium chlorite (ASC) or quaternary ammonium salt preparation (QAS). None of the treatments applied were initially effective at inactivating E coli on lettuce or spinach seeds as the bacterium could be recovered on the subsequent seedlings. However, as the cultivation period progressed, E coli numbers on plants derived from decontaminated seeds declined to below the level of detection. Interestingly, E coli persisted on the surface of lettuce and spinach leaves from inoculated non-treated seeds throughout the 42-day cultivation period. E coli also persisted on coriander derived from inoculated non-treated seeds although it was isolated sporadically on plants derived from QAS-decontaminated seed. E coli numbers progressively declined on celery and watercress regardless of the seed decontamination treatment being applied. No L monocytogenes was recovered from any of the seedlings, possibly because of the growth-suppressing effect of endogenous microflora. The results suggest that effective on-farm controls, such as seed decontamination, should be considered in order to reduce the risk of pathogens associated with salad vegetables and herbs.

The phytochemical composition, antibacterial and antioxidant activities of methanolic extract produced from leaves of rosemary (Rosmarinus officinalis L.) which growing naturally in Libya were assessed. Rosemary extract showed superior scavenging activity in both of Diphenyl-1-picrylhydrazyl (DPPH) (259.67 µmol TE/g dw) and azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) (228.04 µmol TE/g dw). Antimicrobial activity of rosemary against 10 food-borne pathogenic bacteria and food spoilage bacteria were determined and expressed as Minimum inhibitory concentrations (MIC) and Minimum bactericidal concentrations (MBC). Rosemary showed considerable antimicrobial activity against different test bacteria. Namely Bacillus cereus and Enterobacter feacalis were found to be highly susceptible (MBC: ˂3.125 mg/ml) whereas Shigella sonnei and Staphylococcus aureus were the most resistant bacteria (MLC: > 25 mg/ml). Results for phytochemical screening of the methanolic extract of rosemary revealed that total content of phenol and total content of flavonoid were 29.23 mg gallic acid equivalents/gm on a dry basis and 6.59 mg catechin equivalent/g on a dry basis respectively. Additionally, other components were detected consisted of saponin (35.40 mg/gm), tannins (32 mg/gm) and alkaloids (119 mg/gm). Also, rosemary extract (1% aqueous solution) was examined for preservation of Seriola Dumeriri fish fillets. Rosemary extract reduced significantly the total viable, psychrotrophic and coliform counts on fish fillets stored at 2 o C and extended their shelf life up to 6 days in compared with the untrated samples.