Deep‐fat frying under moderate vacuum of potato cylinders

This study evaluates parameters relating to the mass transfer during the frying of potato cylinders at different temperatures (100, 120 and 140 °C) and moderate vacuum (around 25 kPa). In all cases, there is a linear relation between water loss and fat uptake. The parameters relating to the textural and structural modifications show less marked changes in vacuum fried products compared to those fried under atmospheric pressure. The maximum penetration force reaches 30%–40% of the initial hardness in vacuum frying and 10% for atmospheric pressure frying; starch gelatinization and pectin methylesterase enzyme activity reduce more quickly under atmospheric pressure, although after 240 s both values are negligible. The scanning electron microscopy images verify that the surface of potato cylinders fried under vacuum or atmospheric pressure are completely different as a result of the steam being released at different temperatures.     

Theoretical and empirical assessment of evaluation methods of the electric charge transference in welding with covered electrodes

The present work is based on an assessment of experimentally obtained results from the application of different methods of evaluation, reported in the specialised literature, of the electrical charge transference stability in the arc. A simple factorial design, taking the welding current as independent variable, was applied to the process with an AWS A5.1 E6013 electrode. The welds were carried out in the flat position by a gravity device. It was possible to obtain criteria to classify the electrical charge transference stability of the process by digital signal processing and a statistical technique. The outcome was based on visual inspection and morphologic studies. It was concluded that amongst the considered parameters, the average value of the arc conductivity during reignition peaks and the quantity of reignition peaks are the more representative indices, both from statistics and from phenomenological points of view. This finding is validated by the fact that the bead morphology and the stability analysis of the electrical charge transference process coincides with the fact that the 160 A (for 4 mm-diameter electrodes) is the most stable regime.     

In vitro antifungal activity of several antimicrobial compounds against Penicillium expansum

Fungicides used in the prevention and control of mold rots in stored apples are subjected to legal, social, and biological limitations. The aim of this study was to find an alternative to postharvest fungicides currently used in the prevention and control of blue mold rot caused by Penicillium expansum in apples. For this purpose, the antimicrobial activity and MIC of several substances against P. expansum were evaluated in vitro using different end point methods: agar diffusion assay, volatility method, and agar dilution and broth dilution MIC assays. Most of the substances tested are common food ingredients and have a recognized antimicrobial activity. Essential oils, such as thymol, eugenol, citral and cineole, vanillin, sodium hypochlorite, acetic acid, potassium sorbate, and hydrogen peroxide, were the substances evaluated. Thymol and citral were the essential oil components that showed the greatest inhibitory effects. The effectiveness of 5 and 10% hydrogen peroxide in growth inhibition of P. expansum in the agar diffusion assay was total, and its MIC as determined by the agar and broth dilution assays was less than 0.025%. These results indicate that the application of small quantities of hydrogen peroxide to the apple skin might be an alternative to fungicides in the elimination of P. expansum.     

Bistability in Semiconductor Lasers With Polarization-Rotated Frequency-Dependent Optical Feedback

Bistability in the emission frequency of a semiconductor laser subject to orthogonal-polarization optical feedback was recently observed experimentally by Farias in 2005, Phys. Rev. Lett. 94 173902 (2005). A frequency-sensitive filter (Cs-vapor cell) was placed in the way of the feedback beam to spectrally modulate the feedback power. Two different emission frequencies with the same output power were observed. This observation was understood in terms of a model that took into account the line shape of the filter and the empirical linear relation between the feedback-induced frequency shift and the feedback intensity. The model allowed to calculate steady states but not time-varying solutions. Here we present a rate-equation model that takes into account thermal and gain-saturation effects, and predicts a linear variation of the laser frequency with the feedback strength, together with a small power modulation. This model allows to study time-dependent solutions, and in particular, the transition between the two coexisting states. We show that numerical simulations using this model correctly reproduce the previous observed dynamics, and we present new experimental results in good agreement with our model for the laser response under orthogonal feedback     

Alternative Method for Determining O2 and CO2 Transmission Rates Through Microperforated Films for Modified Atmosphere Packs

Most experimental systems for measuring the permeability of microperforated polymeric films are static, mainly because in dynamic systems the small differences in pressure on both sides of the perforation may result in serious errors in the measurements. The O₂ and CO₂ transmission rate through microperforations of different sizes (from 40 × 30 to 350 × 110 µm) were determined in a static and in a dynamic system. In the latter case, rather than the diffusive flow, the hydrodynamic flow generated by the difference in pressure was measured (between 5 and 90 mbar). This was determined by applying Bernouilli's theorem and an experimental equation potentially relating the area of the microperforation with the transmission rate. A comparison of the transmission rates obtained in both cases gives coefficients of determination close to one (>0.993). This means that measuring the hydrodynamic flow can be considered as an alternative for the quantification of the diffusive flow through a microperforation. This is a simple and quick methodology that does not require expensive equipment. Furthermore, this feature enables commercial leak detection equipment to be used to quantify diffusive transmission rates through microperforations. Copyright © 2012 John Wiley & Sons, Ltd.     

Self-feed device behaviour evaluation designed for assessment of operability of coated electrodes

The objective of the present work is to evaluate the effectiveness of a self-feed device for coated electrodes. This device is able to eliminate disturbances from manual operation or the use of automatic control systems during the study of coated electrode behaviour. The conjugation of different methods such as short-circuit time statistical analysis and metallographic analysis (penetration, heat-affected zone, shape and mean distance between successive solidification fronts) together with the analysis of the electric arc and electrode melting parameters allows us to obtain relationships between arc behaviour, mass transfer processes and bead appearance. This permits the extraction of criteria to describe process stability and the behaviour of the feed device employed. An appropriate statistical methodology was obtained to process the ‘duration of the short-circuit’ parameter through an appropriate adjustment of empirical distributions to a log-normal model. The self-feed device for coated electrode welding allows the repeatable and reproducible execution of welding beads in the flat position, keeping the arc length based on physical and chemical characteristics of the electrode during welding trials using 125, 140 and 160 A.