Survival of pathogens in low moisture foods

This work investigated the survival and heat resistance of pathogens (Salmonella spp and Listeria monocytogenes) and a potential surrogate strain (E. faecium NRRL B-2354) in a selection of low moisture foods. The pathogens and the potential surrogate bacteria were inoculated into a selection of low moisture products (confectionery formulation, chicken meat powder, pet food and savoury seasoning, paprika powder and rice flour) and survival during storage as well as heat resistance were determined using glass vials and specially designed thermal cells. This study showed that pathogens can survive well in low moisture foods and survival was dependent on many factors such as water activity (aw), storage temperature and food composition. It was also shown that RpoS regulon plays an important role in Salmonella survival in low moisture foods. A strain lacking an active RpoS was significantly less viable in low moisture foods and significantly less heat resistant than the RpoS+ve strain. This study also showed that the use of E. faecium NRRL B-2354 as a surrogate is feasible for process validation although it has some limitations. It was shown that E. faecium NRRL B-2354 cannot be used as a surrogate in products containing high levels of sugar (confectionery powder) as Salmonella was significantly more heat resistant in this type of product than E. faecium NRRL B-2354. It was also shown that in paprika powder and in rice flour the two most resistant Salmonella strains (S. Enteritidis - PT 30 ATCC BAA-1045 and S. Typhimurium ST30; both RpoS +ve) in some conditions were more resistant than E. faecium NRRL B-2354. This study also showed that survival curves representing microbial survival during storage or during heat processes may not always be linear. In this study, concave upwards, concave downwards and linear curves were recorded and the Weibull model was used to fit raw data and precisely calculate the time required for 5 log reduction in viable numbers

5,5-Dimethyl-2-methyl­seleno-1,3,2-dioxaphospho­rinan-2-one

The title compound, C6H13O3PSe, was obtained in the reaction of 5,5-dimethyl-2-oxo-2-seleno-1,3,2-dioxaphospho­r­inane potassium salt with methyl iodide. The seleno­methyl group is in the axial position in relation to the six-membered dioxaphospho­rinane ring

Optimisation of Saccharomyces cerevisiae BRYC 501 ascospore formation and recovery for heat inactivation experiments

Why was the work done: Ascospores from Saccharomyces cerevisiae BRYC 501 are useful biological indicators for validating the pasteurisation of beer. Ascospores are formed by yeast in response to low nutrient conditions and are characterised by greater resistance to stressors including desiccation, freezing and, during pasteurisation, high temperatures. Accordingly, the sporulation temperature of yeast ascospores, their shelf life, heat resistance and recovery need to be investigated.How was the work done: The role of temperature in sporulation was investigated at 25, 27 and 30°C by measurement of the rate of sporulation over ten days. Shelf life of ascospores was established in deionised water at 1-5°C over 120 days by the measurement of heat resistance in McIlvaine's buffer. The recovery conditions of ascospores were determined using six agars after heat inactivation experiments in McIlvaine's buffer, alcohol free and lager beer.What are the main findings: The sporulation rate of S. cerevisiae ascospores was highest at 27°C, and lowest at 30°C. Heat resistance of ascospores formed at 30°C was low with a D60 value of 200% higher than with the control agar.Why is the work important: Sporulation should be performed at 25°C to produce the maximum number of spores for heat inactivation experiments. Spores can be maintained for 60 days, enabling several experiments to be performed. After heat inactivation experiments, ascospores should be recovered on YEPG agar for 10 days at 27°

O-Pivaloyl diphenyl­seleno­phosphinate

The title compound, C17H19O2PSe, was obtained in the reaction of the diphenyl­monoseleno­phosphinic acid ammonium salt with pivaloyl chloride. The P—Se bond length of 2.0769 (11) Å is normal, while the P—O bond length of 1.650 (3) Å is longer than in related O-alkyl and O-aryl derivatives. One phenyl ring is periplanar to the Se—P—C plane, while the dihedral angle between the two phenyl rings is ca 73°. The carbonyl group is in a synperiplanar position [torsion angle = 8.9 (6)°] to one of the methyl groups of the pivaloyl group. This is the first O-acyl derivative of diphenyl­monoseleno­phosphinic acid characterized by X-ray structural analysis

Geometrical Aberration Suppression for Large Aperture Sub-THz Lenses

Advanced THz setups require high performance optical elements with large numerical apertures and small focal lengths. This is due to the high absorption of humid air and relatively low efficiency of commercially available detectors. Here, we propose a new type of double-sided sub-THz diffractive optical element with suppressed geometrical aberration for narrowband applications (0.3 THz). One side of the element is designed as thin structure in non-paraxial approach which is the exact method, but only for ideally flat elements. The second side will compensate phase distribution differences between ideal thin structure and real volume one. The computer-aided optimization algorithm is performed to design an additional phase distribution of correcting layer assuming volume designing of the first side of the element. The experimental evaluation of the proposed diffractive component created by 3D printing technique shows almost two times larger performance in comparison with uncorrected basic diffractive lens

O-4-Chloro­benzoyl diphenyl­seleno­phosphinate

The title compound, C19H14ClO2PSe, was obtained in the reaction of the diphenyl­monoseleno­phosphinic acid ammonium salt with 4-chloro­benzoyl chloride. The dihedral angle between the P-bonded aromatic rings is 72.64 (14)°. Packing of the mol­ecules in the crystal is reinforced by π–π stacking inter­actions between two inversion-related 4-chloro­benzene rings [centroid-centroid separation = 4.189 (2) Å] and a C—H⋯O interaction also occurs

Anabolic–androgenic steroid dependence: an emerging disorder

Anabolic–androgenic steroids (AAS) are widely used illicitly to gain muscle and lose body fat. Here we review the accumulating human and animal evidence showing that AAS may cause a distinct dependence syndrome, often associated with adverse psychiatric and medical effects.We present an illustrative case of AAS dependence, followed by a summary of the human and animal literature on this topic, based on publications known to us or obtained by searching the PubMed database.About 30% of AAS users appear to develop a dependence syndrome, characterized by chronic AAS use despite adverse effects on physical, psychosocial or occupational functioning. AAS dependence shares many features with classical drug dependence. For example, hamsters will self-administer AAS, even to the point of death, and both humans and animals exhibit a well-documented AAS withdrawal syndrome, mediated by neuroendocrine and cortical neurotransmitter systems. AAS dependence may particularly involve opioidergic mechanisms. However, AAS differ from classical drugs in that they produce little immediate reward of acute intoxication, but instead a delayed effect of muscle gains. Thus standard diagnostic criteria for substance dependence, usually crafted for acutely intoxicating drugs, must be adapted slightly for cumulatively acting drugs such as AAS.AAS dependence is a valid diagnostic entity, and probably a growing public health problem. AAS dependence may share brain mechanisms with other forms of substance dependence, especially opioid dependence. Future studies are needed to characterize AAS dependence more clearly, identify risk factors for this syndrome and develop treatment strategies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78670/1/j.1360-0443.2009.02734.x.pd