Development and Evaluation of a Preliminary Screening Assay for Antibiotic Residues in Meat.

A preliminary screening assay based on a microbial chromogenic reaction was developed to detect common antibiotic residues in meat rapidly. The assay comprised two bioassays: one for Escherichia coli and another for Geobacillus stearothermophilus. The assay was optimized and evaluated for the simultaneous screening of 30 antibiotics from five common antibiotic classes (tetracyclines, aminoglycosides, macrolides, ß-lactams, and quinolones) found in meat. Extraction using phosphate-acetonitrile buffer (pH 7.2) and a delipidating treatment using n-hexane resulted in a high extraction efficacy for the five antibiotics, without affecting the microbial color reaction. A carrier, polyvinyl alcohol (0.1 g/mL); a cross-linking agent, boric acid-sodium tetraborate solution (pH 5.5); and a bacterial suspension with an initial optical density of 1.0 were the optimal embedding conditions for stability, microbial activity, and chromogenic efficiency. The assay exhibited a 6-month shelf life, with detection limits of 40-60, 60-140, 60-100, 20-40, and 40-180 µg/kg for tetracyclines, aminoglycosides, macrolides, ß-lactams, and quinolones, respectively, which met the European Commission (37/2010) requirements for antibiotic residue limits. Our assay results were confirmed using LC-MS/MS with 160 samples, revealing a good correlation. This study demonstrates a reliable, easy-to-use, and economical method for preliminary screening of antibiotic residues in meat. This method may find an immediate application in food safety and general testing laboratories.

Application of artificial neural networks to predict multiple quality of dry-cured ham based on protein degradation.

This study investigated protein degradation and quality changes during the processing of dry-cured ham, and then established the multiple quality prediction model based on protein degradation. From the raw material to the curing period, proteolysis index of external samples were higher than that of internal samples, however, the difference gradually decreased from the drying period to the maturing period. Protein degradation can be used as indicators for controlling quality of the hams. With protein degradation index as input variables, the back propagation-artificial neural networks (BP-ANN) models were optimized, with training function of trainlm, transfer function of logsig in input-hidden layer and tansig in hidden-output layer, and 20 hidden layer neurons. Furthermore, the relative errors of predictive data and experimental data of 12 samples were approximately 0 with the BP-ANN model. Results indicated that the BP-ANN has great potential in predicting multiple quality of dry-cured ham based on protein degradation.

Investigation on reliability of red micro-light emitting diodes with atomic layer deposition passivation layers.

In this study, AlGaInP red light emitting diodes with sizes ranging from 5 to 50 micrometers were fabricated and characterized. The atomic layer deposition technology is applied to coat a layer of silicon dioxide for passivation and protection. The top emission area is covered by ITO layer to maximize the optical output. From the optical measurement, the linewidth and emission peaks shift very little among different current levels (from 30 to 150 A/cm2). High current level lifetests are performed and a 15 µm ALD device can last 27 hours of continuous operation at 100 A/cm2 before their diode junction failed. A much shorter lifetime of 5.32 hours was obtained when the driving current is raised to 400 A/cm2. When the same condition was applied to 15 µm PECVD devices, 25 hours and 4.33 hours are registered for 100 A/cm2 and 400 A/cm2 tests, respectively. The cross-sectional SEM reveals the voids, defects, and dark lines developed during the aging tests, and most of them are caused by top contact failure. The surface layers of ITO and SiO2 were melted and the dark lines which were originated from the top surface propagated through the device and led to the eventual failure of the diode. The optical intensity degradation slopes of different sizes of devices indicate a large device can last longer in this accelerated aging test. The efficiencies of the devices are also evaluated by the ABC model and the fitted bimolecular coefficient ranges from 1.35 to 3.40×10-10 cm3/s.