Effect of combined treatments between gamma irradiation, spices and/or thermal treatment on the viability and enterotoxicity of Staphylococcus aureus

Heat-irradiation combination sequence decreased the thermal resistance of S. Aureus. The synergistic effect increased by increasing either the pre-irradiation thermal exposure time or by increasing the radiation dose. The complete inhibition of bacterial cell was recorded by pre-irradiation thermal treatment at 65, 60 and 55C for 5, 15 and 25 minutes, respectively, at the irradiation dose 0.5 kGy. Combination treatment between irradiation and species decreased the lethal species concentration from 2% to 1% at irradiation dose 0.25 kGy for all examined species and to 0.5% concentration with the irradiation dose 0.5 kGy. The combination treatments between species, temperature and radiation had a great synergistic effect on S. Aureus cells comparable with the individual treatment or with the combination treatment between two factors. There was no variation in the amounts of enterotoxin produced by the organism after treated by the sublethal doses of the combined three factors except in case of mint, which recorded 200% increase for untreated cells

Effect of cephalosporin, kanamycin and irradiation on total lipids, phospholipids, neutral lipids and sterols contents of bacillus megaterium and E. coli

Cephalosporin treatment decreased total, phospho and neutral lipids of B. Megaterium and E. Coli in both solid and liquid media, expect neutral lipids of E. coli treated with cephalosporin. Total neutral and sterols contents of B. megaterium treated with kanamycin decreased by using solid media and increased in liquid media, while phospholipids increased when both media are used. On the other hand, all lipid fractions of E. coli treated with kanamycin increased, when both solid and liquid media were used. Qualitative and quantitative variations were noticed in the fatty acids pool of the non-treated and treated B. Megaterium and E. coli. In the treated inocula, one or more fatty acids disappeared from the treated cells. Percentage of the saturated fatty acids of control and treated B. Megaterium were less than E. Coli. A significant increase in total, neutral lipids and sterols contents were recorded in cells of B. Megaterium arising from irradiated inocula, while there was a significant decrease in the phospholipids contents of irradiated inocula. On the other hand, E. coli behaved in opposite direction of B. Megaterium. Radiation increased the percentage of saturated fatty acids of both organisms than control

Role of gamma irradiation for self-life extension and improvement the hygienic quality of fresh fish

This work aimed to study the role of gamma irradiation [1.5 and 3 kGy] in improving hygienic quality of fresh Bolti fish [Tilapia nilotica] stored at refrigerator temperature [3C] in prolonging the shelf-life extension and eliminating the pathogenic microorganisms. The results revealed that an irradiation dose of 3.0 kGy was most effective, not only for reducing the total contaminated bacteria, fungi and yeasts but also for a complete elimination of pathogenic Staph. aureus and E. coli; while Strep. faecalis showed some resistance during 30 days of storage without undesirable changes in their organoleptic properties compared with the control samples without any additives. Exposure doses of 1.5 and 3.0 kGy appeared to be most effective in reducing the viable counts of proteinase producing bacteria after 12 days of cold storage by 98.8% and 99.9% respectively, while a complete sterilization occurred at 3.0 kGy

Irradiation for shelf-life extension and improvement of the hygienic quality of cold-smoked herrings and hot-smoked eels

A shelf-life extension and improving the hygienic quality of cold- smoked herrings and hot-smoked eels were done using gamma irradiation. The preparation of each product was described. Dose level of 5 kGy extended the shelf-life of cold-smoked herrings with 48% moisture and 8% salt up to 4 months at room temperature compared by one month for the unirradiated samples. This irradiation dose was also sufficient and efficient for eliminating the risk resulting from pathogenic bacteria and mycotoxigenic fungi, which may be present in smoked fish. Application of 7.5 kGy of gamma rays appeared to be effective and sufficient for eliminating the anaerobic and pathogenic bacteria in the hot-smoked eels [60% moisture and 1.5% salt] packed in polyamide- polyethylene bags under vacuum condition. It has remarkable effect in decreasing the total aerobic bacteria and hence extending the shelf- life of smoked eels to more than 60 days under cold storage [3 +/- 1C] compared by only 15 days for the unirradiated samples. This dose greatly affect the flavor of this product. Irradiation dose of 5.0 kGy appeared to be optimum for extending the shelf-life and improving the hygienic quality of hot-smoked eels without changing their attractive flavor

Incidence of toxic and pathogenic micro organisms in different Egyptian and Saudi Arabian food commodities and their decontamination by gamma irradiation

The bacterial and fungal contamination were examined in 264 food and feed samples, collected from different localities of Cairo [Egypt] and Abha [Asir Region, Kingdom of Saudi Arabia]. The total aerobic bacterial counts in tested samples ranged from10[3] to 10[7] per gram. Coliforms were not detected on all examined samples. The aerobic spore formers were identified as Bacillus cereus, B. megaterium, B. pumilus and B. subtilis. The total counts of moulds ranged from 10 2 to 10 5 per gram. The most common fungal isolates were identified as Aspergillus glaucus, A. restrictus, A. flavus, A. fumigatus, A. niger, A. ochraceus and different Penicillium spp. Candida alb leans and C. tropicals were the predominant yeasts/isolated from cereal grains with total count ranged from 10[4] to 10[5] per gram. Aflatoxins B1 and B2 were detected in Egyptian and Saudi Arabian maize and black pepper samples. Furthermore, maize and black pepper samples were the most frequent foods contaminated with aflatoxigenic strains of A flavus. An irradiation dose of 10 KGy decreased the spore-forming o bacteria below 10[3] per gram, whereas the dose required to inhibit completely the natural fungal flora ranged from 4 to 6 KGy