Effect of Cooking Method and Ethanolic Tocopherol on Oxidative Stability and Quality of Beef Patties During Refrigerated Storage (Oxidative Stability of Cooked Patties)

ABSTRACT: Incorporation of δ-tocopherol using an ethanolic carrier to control lipid oxidation in impingement and ohmic cooked beef patties was evaluated, and quality characteristics were determined. Ethanolic δ-tocopherol delayed oxidative deterioration of cooked beef patties in both cooking methods. Ohmic cooked samples developed significantly higher ( P < 0.05) thiobarbituric acid-reactive substances (TBARS) than impingement-cooked samples. Formation of TBARS significantly ( P < 0.05) increased with storage time in both cooking treatments. Cooking method significantly ( P < 0.05) influenced color and textural attributes of beef patties. Samples cooked by ohmic heater were lighter, displaying significantly ( P < 0.05) larger L * color values. Additionally, ohmic samples were harder, chewier, and more cohesive ( P < 0.05) than samples cooked with an impingement oven. Exogenous addition of ethanolic tocopherol can delay lipid oxidation and improve quality of cooked meat products.     

Use of time-temperature integrators and predictive modeling to evaluate microbiological quality loss in poultry products

The purpose of this study was to characterize the kinetics of the spoilage process of chicken drumsticks in order to evaluate the application of an enzyme process-based time-temperature integrator (TTI) as a continuous quality monitor of poultry products. Shelf life studies were conducted at several temperatures (3 to 20 degrees C) to characterize (i) the poultry spoilage process as a function of total aerobic bacteria and Pseudomonas species populations and (ii) the TTI chroma response function. Two types of poultry products were examined: ice-packed and chill-packed drumsticks. An enzyme-based TTI with a color change response from green to yellow was used. Activation energies for each of the poultry products and each of the bacterial populations were as follows: 21.8 +/- 1.6 kcal/mol (ca. 91.2 +/- 6.7 kJ/mol) for ice-packed drumsticks and total aerobic population, 18.8 +/- 4.5 kcal/mol ca. 78.7 +/- 18.8 kJ/mol) for ice-packed drumsticks and Pseudomonas spp., 17.0 +/- 2.3 kcal/mol (ca. 71.1 +/- 9.6 kJ/mol) for chill-packed drumsticks and total aerobic population, and 14.1 +/- 3.6 kcal/mol (ca. 59.0 +/- 15.1 kJ/mol) for chill-packed drumsticks and Pseudomonas spp. The activation energy calculated for the TTI, 19.1 +/- 1.8 kcal/mol (ca. 79.9 +/- 7.5 kJ/mol), was determined to be adequately close to that of the poultry spoilage process to make effective quality predictions possible. Initial bacteria levels on the chicken drumsticks were uniform and not judged as important limiting factors in the application of TTIs to poultry products. Because the poultry spoilage process was reasonably characterized on the basis of Arrhenius kinetics, there is further need to conduct validation studies to determine the ability of TTIs to provide a continuous quality monitoring system.     

A MULTITAXONOMIC APPROACH TO UNDERSTANDING LOCAL‐ VERSUS WATERSHED‐SCALE INFLUENCES ON STREAM BIOTA IN THE LAKE CHAMPLAIN BASIN,VERMONT, USA

Twenty‐one stream reaches in northwestern Vermont were surveyed to assess the relative influence of local‐ and watershed‐scale variables on stream biotic assemblages including fish, aquatic macroinvertebrates and birds. Data were collected during the summers of 2003 and 2004 and included quantitative and qualitative geomorphic and habitat assessments (local‐scale) and land‐use characterization and modelled annual flow and sediment loading (watershed‐scale). Biotic assemblages were surveyed to capture characteristics related to abundance, diversity and composition. Principal components analysis (PCA) was used to generate sets of factors representing unique scenarios of geophysical data derived from various spatial extents within the watershed. These factors were then used as the independent variables in multiple regression models using the biotic data as the dependent variables. Forty significant models were built from the combination of the eight scenarios and 11 dependent variables. Fish assemblage diversity and composition were influenced by a combination of local‐scale and watershed‐scale variables; however, the qualitative local data were more predictive than the quantitative data. Local‐scale data and sediment (model‐derived) were important factors in building significant macroinvertebrate models. Bird abundance and species richness were best predicted using local geomorphic characteristics and the qualitative local data. Our results reinforce the concept that whereas both local‐ and watershed‐scale variables affect stream biota, their relative influence depends upon the individual ecology of each taxon. In order to address these issues, comprehensive watershed management, restoration and conservation plans would benefit from assessments at multiple scales and from geomorphological, watershed and multitaxonomic perspectives. Copyright © 2010 John Wiley & Sons, Ltd.     

PEGylated Cationic Serum Albumin for Boosting Retroviral Gene Transfer

Retroviral vectors are common tools for introducing genes into the genome of a cell. However, low transduction rates are a major limitation in retroviral gene transfer, especially in clinical applications. We generated cationic human serum albumin (cHSA) protected by a shell of poly(ethylene glycol) (PEG); this significantly enhanced retroviral gene transduction with potentially attractive pharmacokinetics and low immunogenicity. By screening a panel of chemically optimized HSA compounds, we identified a very potent enhancer that boosted the transduction rates of viral vectors. Confocal microscopy revealed a drastically increased number of viral particles attached to the surfaces of target cells. In accordance with the positive net charge of cationic and PEGylated HSA, this suggests a mechanism of action in which the repulsion of the negatively charged cellular and viral vector membranes is neutralized, thereby promoting attachment and ultimately transduction. Importantly, the transduction‐enhancing PEGylated HSA derivative evaded recognition by HSA‐specific antibodies and macrophage activation. Our findings hold great promise for facilitating improved retroviral gene transfer.     

Development of Molecularly Imprinted Polymer in Porous Film Format for Binding of Phenol and Alkylphenols from Water

Molecularly imprinted polymers (MIPs) were fabricated on glass slides with a “sandwich” technique giving ~20 μm thick films. Methanol/water as a solvent, and polyethyleneglycol and polyvinylacetate as solvent modifiers, were used to give a porous morphology, which was studied with scanning electron microscopy and gravimetric analysis. Various MIPs were synthesized through non-covalent imprinting with phenol as the template; itaconic acid, 4-vinylpyridine, and styrene as monomers; ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and pentaerythritol triacrylate (PETA) as cross-linkers. Binding and imprinting properties of the MIPs were evaluated based on phenol adsorption isotherms. Since phenol has only one weakly acidic hydroxyl group and lacks unique structural characteristics necessary for binding specificity, the preparation of selective MIPs was challenging. The recognition of phenol via hydrogen bonding is suppressed in water, while hydrophobic interactions, though promoted, are not specific enough for highly-selective phenol recognition. Nevertheless, the styrene-PETA MIP gave modest imprinting effects, which were higher at lower concentrations (Imprinting Factor (IF) = 1.16 at 0.5 mg·L⁻¹). The isotherm was of a Freundlich type over 0.1–40 mg·L⁻¹ and there was broad cross-reactivity towards other structurally similar phenols. This shows that phenol MIPs or simple adsorbents can be developed based on styrene for hydrophobic binding, and PETA to form a tighter, hydrophilic network.     

Neutron radiography and current distribution measurements for studying cathode flow field properties of direct methanol fuel cells

The influence of the cathode flow field properties on the water distribution and performance of direct methanol fuel cells (DMFCs) was studied. All measurements were performed with DMFC stack cells (A = 314.75 cm²). The local and temporal water distributions in the flow field channels during DMFC operation were visualized by means of through‐plane neutron radiography. Current and temperature distributions were measured simultaneously by the segmented cell technology. Additionally, the time‐dependent current distribution, cell performance and pressure drop were measured. Cathode flow field designs with channel and grid structures were compared. The cathode flow field channels were impregnated by either hydrophobizing or hydrophilizing agents or used as received. It turned out that hydrophobized and partially also untreated flow fields cause large water droplets in the cathode channels. The water droplets cause a blocking of the air flow and consequently a lower and more unstable (fluctuating) performance, less steady current and temperature distributions, and higher pressure drops between cathode inlet and outlet. Because of their two‐dimensional design, grid flow fields are less prone to water accumulations. The best results are achieved with a hydrophilized grid flow field that has a channel depth and width of 1.5 mm each (‘C‐GR15’). Copyright © 2013 John Wiley & Sons, Ltd.     

Triplet Harvesting from Intramolecular Singlet Fission in Polytetracene

Singlet fission (SF), a promising mechanism of multiple exciton generation, has only recently been engineered as a fast, efficient, intramolecular process (iSF). The challenge now lies in designing and optimizing iSF materials that can be practically applied in high‐performance optoelectronic devices. However, most of the reported iSF systems, such as those based on donor–acceptor polymers or pentacene, have low triplet energies, which limits their applications. Tetracene‐based materials can overcome significant challenges, as the tetracene triplet state is practically useful, ≈1.2 eV. Here, the synthesis and excited state dynamics of a conjugated tetracene homopolymer are studied. This polymer undergoes ultrafast iSF in solution, generating high‐energy triplets on a sub‐picosecond time scale. Magnetic‐field‐dependent photocurrent measurements of polytetracene‐based devices demonstrate the first example of iSF‐generated triplet extraction in devices, exhibiting the potential of iSF materials for use in next‐generation devices.