Inactivation of Listeria monocytogenes on Unpackaged and Vacuum-Packaged Chicken Frankfurters Using Pulsed UV-Light

ABSTRACT:  The effectiveness of pulsed UV-light on the microbial load and quality of unpackaged and vacuum-packaged chicken frankfurters was investigated. Samples were inoculated with  Listeria monocytogenes  Scott A on the top surfaces, and then treated with pulsed UV-light for 5, 15, 30, 45, and 60 s at 5, 8, and 13 cm distance from the quartz window in a pulsed UV-light chamber. Log reductions (CFU/cm²) on unpackaged samples were between 0.3 and 1.9 after 5-s treatment at 13 cm and 60-s treatment at 5 cm, respectively. Log reductions on packaged samples ranged from 0.1 to 1.9 after 5-s treatment at 13 cm and 60-s treatment at 5 cm, respectively. The temperature changes of samples and total energy (J/cm²) received at each treatment condition were monitored. The extent of lipid peroxidation and the color were determined by thiobarbituric acid-reactive substances (TBARS) test and CIELAB color method, respectively. Lipid peroxidation of samples did not change significantly ( P  > 0.05) after mild (5-s treatment at 13 cm) and moderate (30-s treatment at 8 cm) treatments. Significant differences ( P  < 0.05) in color parameters were observed after treatments of both unpackaged and packaged samples. Packaging material was also analyzed for mechanical properties. The elastic modulus, yield strength, percent elongation at yield point, maximum tensile strength, and percent elongation at break did not change significantly ( P  > 0.05) after mild treatment. Overall, this study demonstrated that pulsed UV-light has a potential to decontaminate ready-to-eat (RTE) poultry-based food products.     

An Innovative Device for Quantification of Percolation and Sieving Segregation Patterns–Single Component and Multiple Size Fractions

ABSTRACT

Segregation occurs during most particulate materials-related unit operations including mixing, conveying, discharging, filling, and compaction. A redesigned second-generation primary segregation shear cell (PSSC-II) was fabricated to simulate and quantify percolation and sieving mechanisms-based segregation. Several binary mixtures were tested to quantify the effect of size ratios and absolute size. The constituents of binary mixtures studied were spherical glass beads. Three binary size ratios, 4:1, 6:1, and 8:1, were tested. For a given size ratio, three different absolute coarse (710–850, 1000–1200, and 1400–1700 μm) to fine particle sizes were studied. The experimental results showed that the PSSC-II was capable of quantifying segregation potential for various materials. Several physical parameters such as segregation rate (SR), phase of segregation rate (PSR), distribution of segregation rate (DSR), maximum segregation rate (MSR), and normalized segregation rate (NSR) were created to describe the quantity of segregation to a certain level. It was concluded that: (1) Generally, the segregation rates increase with the increase in size ratio. A linear relationship between NSR and size ratio exists for glass beads (R² = 0.99). (2) Segregation rate also increases with absolute size. NSR increases linearly with absolute size for glass beads (R² = 0.99). Furthermore, a quantitative relationship exists between certain size ratios and segregation rates, i.e., while size ratio increased two-fold from 4:1 to 8:1, the NSR increased approximately six-fold. (3) The largest magnitude of the NSR occurred where both absolute size and size ratio were at their largest values. (4) The DSR for the binary mixture of glass beads was mainly concentrated in the center region of the shear box for larger size ratios such as 8:1 and 6:1, whereas, for smaller size ratios such as 4:1, the DSR is approximately uniformly distributed. (5) Both duration of lag phase (DLP) and duration of acceleration phase (DAP) decrease with increase in size ratios and in absolute sizes. The smaller the DLP and DAP, the larger the MSR.     

Percolation Segregation in Binary Size Mixtures of Spherical and Angular-Shaped Particles of Different Densities

Percolation segregation in binary size mixtures for two particulate types, urea (spherical) and potash (angular), were studied. Materials chosen are major raw ingredients of blended fertilizer that represent two extremes based on shape and density. In this study, the coarse and fine particles were classified using particle sizes larger and smaller than 2,000 μm, respectively. Three coarse mean sizes (3,675 μm, 3,075 μm, and 2,580 μm) for both spherical and angular particles and three fines mean sizes (2,180 μm, 1,850 μm, and 1,550 μm) for angular particles and two fines mean sizes (2,180 μm and 1,850 μm) for spherical particles were selected for tests. Size ratio for binary size mixture is defined as the ratio of mean size of coarse to fine particles. Binary mixed samples of coarse and fine particles were placed into the shear box of the primary segregation shear cell (PSSC-II) very gently to avoid segregation. Percolation segregation was quantified using PSSC-II. Based on experimental results, the segregated fines mass, normalized segregation rate (NSR), and segregation rate of fines for binary mixtures were higher for larger size ratios as expected (2.4 > 2.0 > 1.7). The NSR is defined as the amount of fines percolated from initial fines present in the binary mixture based on total time of PSSC-II operation (kg/kg-h). Segregation rate was the highest and lowest for mixing ratios 33:67 and 67:33, respectively, when coarse mean size was 3,675 μm, where mixing ratio for binary mixtures is the ratio of the mass of coarse particles to the mass of fine particles. For the same size ratio, segregated fines mass for coarse-fine size combinations in the binary mixtures of urea and potash were significantly different (p < 0.05). Segregated fines mass of potash and urea particles was significantly different for the same size ratio and the same coarse sizes (p < 0.05). Percent segregated fines of angular particles (59%) was higher than that of spherical particles (45%) for the size ratio 2.0 and coarse mean size of 3,675 μm.     

Uniformity Differentiation Analysis of Powder Deposition Characteristics in Circular and Rectangular Shallow Dies Using Feed Shoe with Square Cross-Section

The inhomogeneity of the pressure distribution after completion of the filling process might create tablet and compact quality issues. Generating a uniform precompaction powder deposition into a die would minimize one source of tablet quality issues. This article determines the characteristics of the deposition process into a rectangular die and a circular shallow die, using a feed shoe with a square cross-section tube. A series of experiments were performed that determined the cumulative influence of particle size, die geometry, and feed shoe speed on uniformity of pressure distribution at the end of filling process. For uniformity comparison, the profiles of pressure distribution at the end of filling process were displayed as contour plots. Symmetry analysis, variance metrics, and uniformity analysis were implemented to quantify the deposition characteristics. Feed shoe speeds of 20 and 100 mm/s were used to fill the die. Due to their differing particle characteristics and importance, a pharmaceutical powder filler (microcrystalline cellulose-Avicel PH102) and a battery powder mixture (BPM) were used as test materials. The results showed that (1) contour plot was the most reliable method for evaluating uniformity deposition characteristics in dies; (2) based on contour plot analysis, BPM deposition at 100 mm/s feed shoe speed for circular shallow dies resulted in the most uniform pressure distribution among all, that is, 64% uniformity at ±20 dm (decimeter) resolution and 14.7% coefficient of variation (COV); (3) Avicel deposition at 20 mm/s feed shoe speed for circular dies had the least uniformity (46%); (4) rectangular dies generally had lower symmetry index (61%) in comparison with circular dies, which was attributed to sharp edges of rectangular die, that is, particles trapped in corners generated higher stresses inside the rectangular die versus circular die.     

Uniformity Differentiation Analysis. Part 1: Powder Deposition Characteristics in Rectangular Shallow Die Using Feed Shoe with Circular Cross Section

The process of die filling is a significant unit operation in many industries. Inhomogeneity of distribution such as in mass, bulk density, and pressure might cause many tablet and compact quality issues, such as lamination, capping, and distortion. No systematic investigations have been done to evaluate pressure distribution characteristics in dies with small aspect ratios (ratio of fill height to characteristic cross section dimension <0.5). In order to evaluate pressure distribution during filling of shallow dies, a circular cross section feed shoe was used at two speeds. The deposition characteristics of two powders with differing particle characteristics were studied in this research. The second-generation pressure deposition tester (PDT-II) was used to measure the two powders' pressure distribution characteristics. A battery powder mixture (BPM) and microcrystalline cellulose (Avicel PH102) were used to fill a rectangular shallow die 32 × 30 mm in dimension and 6.5 mm deep. Feed shoe speeds of 20 and 100 mm/s were used to fill the die. Symmetry analysis, variance metrics, Gini coefficient, and uniformity analysis were used to quantify the deposition characteristics. The results showed that (1) the contour plot was the most reliable method for measuring powder deposition characteristics; (2) the leeward and forward pressure distrbution comparisons generated a larger symmetry index than the front and back pressure distribution; (3) based on contour plot analysis, BPM at 100 mm/s feed shoe speed resulted in the most uniform pressure distribution (64% uniformity at +/?20 dm (decimeter) resolution) among all; (4) feed shoe speed greatly influenced pressure distribution uniformity inside the die; and (5) the high stress zone was mostly observed in forward and back regions inside the die.     

Development of a Medium Pressure Flexible Boundary Cubical Triaxial Tester

ABSTRACT

A medium pressure flexible boundary cubical triaxial tester has been designed and fabricated. In this tester, air pressure up to 70 MPa can be applied to all six surfaces of a 50X50X50 mm cube-shaped powder specimen via flexible rubber membranes. Pressure in a vertical direction (top-bottom faces of the powder specimen) and the pressure in a horizontal direction can be controlled independently. This tester can handle displacements as large as 50 mm in each of the three principal directions. Hydrostatic triaxial compression (HTC) tests. conventional triaxial compression (CTC) tests, and mean effective stress (MES) tests will be conducted on three powders, including a pharmaceutical powder, a ceramic powder, and an aluminum oxide powder. HTC tests will be conducted at 0 to 20 MPa, with 3 loading-unloading cycles. CTC and MES tests will be conducted at several pressure levels from 0 to 20 MPa.     

Simultaneous optimisation of multiple performance characteristics in micro-EDM drilling of titanium alloy

Micro-electrical discharge machining (micro-EDM) has become a widely accepted non-traditional material removal process for machining conductive and difficult-to-cut materials effectively and economically. Being a difficult-to-cut material, titanium alloy suffers poor machinability for most cutting processes, especially the drilling of micro-holes using traditional machining methods. Although EDM is suitable for machining titanium alloys, selection of machining parameters for higher machining rate and accuracy is a challenging task in machining micro-holes. In this study, an attempt has been made for simultaneous optimization of the process performances like, metal removal rate, tool wear rate and overcut based on Taguchi methodology. Thus, the optimal micro-EDM process parameter settings have been found out for a set of desired performances. The process parameters considered in the study were pulse-on time, frequency, voltage and current while tungsten carbide electrode was used as a tool. Verification experiments have been carried out and the results have been provided to illustrate the effectiveness of this approach.     

Molecular identification of marine yeast and its spectroscopic analysis establishes unsaturated fatty acid accumulation

Marine microbes are competent organisms, some of which can accumulate large amounts of lipids. A yeast strain, Rhodotorula mucilaginosa AMCQ8A was isolated from the marine water of the Queenscliff region, Victoria, Australia. The yeast isolate was identified by sequencing 18s rDNA genes. Scanning electron microscopy images revealed scars on the surface of the yeast cells. The Fourier transform infrared spectroscopy microspectroscopy studies demonstrated the presence of unsaturated fatty acids by differential microscopic analysis. The sharp band at 1745?cm(-1) was represented by ν(CO) stretches of ester functional groups from lipids and fats, and therefore indicated the presence of total lipids produced by the cells. Over 65% of the fatty acids from the yeast strain were analyzed as C(16) and C(18:1) with omega-3 content from about 6% to 7%. Thus, this marine-derived yeast could be a potential source of lipids, including omega-3 fatty acids.     

Combustion-synthesized ferrites and ferroelectrics for microwave applications

The individual phases of Ni_{1 ? x} Cd _x Fe₂O₄ (x = 0.2, 0.4, 0.6) ferrite and Ba_0.8Sr_0.2TiO₃ ferroelectric (BST phase) were successfully prepared by autocombustion route. The oscillatory behavior of transmittance for the Ni-Cd ferrite was observed at about 0.44 at 8.2 GHz. The absorption study depicts the hopping phenomena of microwaves through the Ni-Cd phase. The dependence of microwave conductivity on ferrite content was discussed. The dielectric permittivity of Ni-Cd ferrites varied between 10 and 30. Compared to the Ni-Cd phase, the transmittance of the Ba_0.8Sr_0.2TiO₃ phase was found to be low. The dip in reflection loss for Ba_0.8Sr_0.2TiO₃ is equivalent to the minimum reflection or the maximum absorption of the microwave power for BST phase. The maximum microwave conductivity for Ba_0.8Sr_0.2TiO₃ was found to be about 0.459 S/cm. The high microwave permittivity for Ba_0.8Sr_0.2TiO₃ had a value of about 120.21.