Application of a novel immunomagnetic separation-bacteriophage assay for the detection of Salmonella enteritidis and Escherichia coli O157:H7 in food

Salmonella infection is the second most prevalent cause of foodborne illness in most developing countries. Meat, poultry, and dairy products are frequently implicated in outbreaks. The objective of this study was to apply a novel immunomagnetic separation (IMS)-bacteriophage assay to the detection of Salmonella enteritidis in artificially inoculated skimmed milk powder, chicken rinses, and ground beef. In all food types tested, the IMS-bacteriophage assay was able to detect an average of 3 CFU of S. enteritidis in 25 g or ml of food sample. Total assay time including pre-enrichment is about 20 h. The results indicate that the IMS-bacteriophage assay is a rapid and sensitive means of detecting S. enteritidis in these foods. The assay was successfully adapted to the detection of Escherichia coli O157:H7 and was able to detect E. coli in ground beef at the lowest inoculation level tested, 2 CFU/g. The assay was also adapted to the simultaneous detection of S. enteritidis and E. coli. The results indicate that the IMS-bacteriophage assay shows promise for the simultaneous detection of these pathogens, but further development work would be necessary to improve sensitivity and produce reliable results at low inoculation levels.     

Mercury stable isotopes in seabird eggs reflect a gradient from terrestrial geogenic to oceanic mercury reservoirs

Elevated mercury concentrations ([Hg]) were found in Alaskan murre (Uria spp.) eggs from the coastal embayment of Norton Sound relative to insular colonies in the northern Bering Sea-Bering Strait region. Stable isotopes of Hg, carbon, and nitrogen were measured in the eggs to investigate the source of this enrichment. Lower δ(13)C values in Norton Sound eggs (-23.3‰ to -20.0‰) relative to eggs from more oceanic colonies (-20.9‰ to -18.7‰) indicated that a significant terrestrial carbon source was associated with the elevated [Hg] in Norton Sound, implicating the Yukon River and smaller Seward Peninsula watersheds as the likely Hg source. The increasing [Hg] gradient extending inshore was accompanied by strong decreasing gradients of δ(202)Hg and Δ(199)Hg in eggs, indicating lower degrees of mass-dependent (MDF) and mass-independent Hg fractionation (MIF) (respectively) in the Norton Sound food web. Negative or zero MDF and MIF signatures are typical of geological Hg sources, which suggests murres in Norton Sound integrated Hg from a more recent geological origin that has experienced a relatively limited extent of aquatic fractionation relative to more oceanic colonies. The association of low δ(202)Hg and Δ(199)Hg with elevated [Hg] and terrestrial δ(13)C values suggested that Hg stable isotopes in murre eggs effectively differentiated terrestrial/geogenic Hg sources from oceanic reservoirs.     

Effects of Oregano Oil Brine Enhancement on Quality Attributes of Beef Longissimus dorsi and Semimembranosus Muscles from Various Age Animals

ABSTRACT: The study reports whether or not oregano oil can reduce lipid oxidation and evaluate palatability variations in beef longissimus dorsi and semimembranosus muscles from various age animals (approximately 18 mo; 18 M, 30 to 60 mo; 30 M, and >60 mo; 60 M). Six muscles of each age group were halved and enhanced with a control brine containing no antioxidants (CN) or a brine containing oregano oil (OR), cut into steaks, and stored in modified atmosphere packaging for 0, 4, 7, and 11 d. Each sampling day, surface color (Minolta L*, a*, b*), lipid oxidation (TBARS), cook yield, sensory analysis, and Warner–Bratzler shear force (WBSF) were measured. OR enhancement decreased TBARS values and slowed the rate of decline in a* values (P < 0.05), but had no effect on WBSF, or sensory tenderness and juiciness scores (P > 0.05) compared to CN steaks. OR steaks had less rancidity detection, more off-flavor, lower overall acceptability in sensory analysis (P < 0.05). This indicated oregano oil can effectively reduce lipid oxidation and extend shelf-life of meat products, but further investigation would be needed to avoid off-flavor and acceptability of product quality. Practical Application: Decreases in meat consumption have led the meat industry to become more innovative in product development. Reducing lipid oxidation is a viable method to reduce rancidity, and improving product acceptability. Our research indicated that although oregano oil did reduce lipid oxidation, the adverse effects of flavor were too great, and thus would not be tolerable in fresh meat products at this concentration. However, there is potential to use oregano oil at lower concentrations and in a variety of processed products which could be beneficial to further the use of natural antioxidants.