Cooking mussels (Mytilus galloprovincialis) by steam does not destroy the infectivity of Cryptosporidium parvum

The consumption of shellfish has increased considerably worldwide, with an associated increase in foodborne illnesses. Among the bivalves, the mussels are usually cooked by steam, which constitutes a typical dish in several regions. In this article, we demonstrate that this preparation is not sufficient to destroy completely the infectivity of Cryptosporidium parvum. Oocysts recovered from experimentally contaminated mussels (Mytilus galloprovincialis) were infectious to neonatal mice after cooking. Although, to date, no official cases of cryptosporidiosis linked to shellfish consumption have been reported, we recommend that people with reduced immunity avoid this type of food because they are at high risk of being infected with Cryptosporidium spp. after eating raw or undercooked contaminated bivalves.     

Hydrogen plasma treatment of very thin p-type nanocrystalline Si films grown by RF-PECVD in the presence of B(CH3)3

We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (∼20 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film.     

Freezing rate simulation as an aid to reducing crystallization damage in foods

In food freezing processes the presence of large ice crystals is a serious drawback when a good final quality of the product is desired. To study the size and distribution of those crystals, a large piece of pork muscle has been frozen by liquid nitrogen evaporation. A mathematical model to simulate different cooling rates at the surface of the product was solved using a finite element method; this model satisfactorily fitted experimental data and predicted local freezing rates at different locations in the meat tissue. The model was applied to find the freezing rates that led to a good quality product, related to an optimum distribution of small ice crystals located inside and outside the tissue fibres.     

Accumulation mechanism for metal chalcogenide nanoparticles at Hg0 electrodes: copper sulfide example

Mercury electrodes preconcentrate metal chalcogenide nanoparticles effectively, enabling their detection at submicromolar concentrations (as Sigma chalcogenide) by adsorptive cathodic stripping voltammetry. Understanding the unique behavior of nanoparticle analytes during preconcentration is critical for lowering detection limits and for quantification. A multistep mechanism is proposed on the basis of accumulation experiments with polydisperse copper sulfide (CuxS) nanoparticles. Particles first diffuse and adsorb at the Hg0 surface. When both the electrode and particles have negative surface potentials, this process resembles charge-impeded coagulation, obeying the Schulze-Hardy rule at various electrolyte strengths. Consequently, accumulation rates are surprisingly sensitive to electrolyte concentration. Choosing accumulation potentials where the electrode and particles have opposite surface potentials greatly improves collection efficiency, especially for the smallest particles. After adsorption, particles undergo transformations. One product is a more stable (harder to reduce) form of CuxS, interpreted to consist of adclusters or adlayers. A very significant (approximately 0.3 V) negative shift in reduction potential results from this transformation. Loss of analyte to at least one nonelectroactive product is also observed. Loss is greatest for the smallest particles and is sensitive to choice of accumulation potential. To improve accumulation efficiency, accumulation potentials more positive that the potential of zero charge of Hg electrodes are advantageous but care must be taken to remove dissolved chalcogenides under these conditions in order to avoid artifacts.     

Interface sensor based on computer vision: Fine tuning using a fluidized bed

The fine tuning of a sensor designed to locate interfaces using a two‐dimensional gas–solid fluidized bed (FB) as reference is described. The sensor works through computer vision and consists of a charge coupled device camera that is placed alongside the bed and, as the human eye would do, first establishes a straight segment of the bed's top surface to define the phase boundary and then through pattern recognition continuously scans the interface in search of a similar pattern. The field of view is 582 × 752 pixels². The experimentally measured Pixel size is 216 × 208 μm². The device allows for experimentally obtaining the position of the probe with a resolution of ± 0.01 pixels at 25 Hz. We also describe its use to measure the height of the FB and observe a linear relationship with fluidization velocity. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Evaluation of the electrical impedance spectroscopy (EIS) equipment for ham meat quality selection

The objective of this study was to evaluate the electrical impedance spectroscopy (EIS) prototype, to select the hams on the basis of meat quality characteristics in commercial conditions. Measurements of meat quality were made on 95 commercial hams (11.10±0.76 kg) to evaluate quality characteristics [ham weight, conformation (H), fat thickness in the rump (FTR), visual fatness (VF), pH(45), electrical conductivity (QM(45)) and ultimate pH (pH(24,) pH(36)) in the semimembranosus muscle]. The electrical parameters, Ro, Rinf, Ratio (Rinf/Ro), Fc and α, were obtained with the EIS equipment and was applied in five different regions of the ham (M, SM, M1, M2 and AD) at 36 h post-mortem. Principal component (PC) analysis has been used to describe the relationships between meat quality and electrical parameters in the ham meat. Two regions were selected, SM and M, showing the best correlations with pH(45) and fat characteristics in relation to electrical parameters Rinf and Ratio, respectively. Multiple regression analysis of the data confirmed that electrical variables, Ratio, α and Fc contributed to predict pH(45) (R(2)=0.50). In order to better predict visual fatness (VF), conformation and ham weight were included in the multiple regression. A R(2) of 0.59 was obtained with H, Rinf, ham weight and α. In conclusion, the results of this study have demonstrated that ratio in the SM region may classify with 88.46% accuracy the technologically normal meat (pH(45) > 6.10) from the PSE meat. In relation to visual fatness of the ham 84.21% of the samples with a Rinf in the M region > 56 had a score of > 2.5.     

Effect of addition of sucrose and aspartame on the compression resistance of hydrocolloids gels

The effect of adding sucrose (5–25% w/w) and aspartame (0.04–0.16% w/w) on the compression resistance of three hydrocolloid gelled systems: κ‐carrageenan, gellan gum and κ‐carrageenan/locust bean gum at three different concentrations (0.3, 0.75 and 1.2% w/w) was studied. Sucrose addition increased true rupture stress in the three‐gelled systems, this effect being stronger in gellan gels. The deformability modulus increased with sucrose concentration in gellan gels, but not in the other systems. Rupture stress and deformability modulus increased with the addition of sucrose only in the harder gels (0.75 and 1.2% w/w). The effect of sucrose addition on the true rupture strain was significant but, in general, not important, mainly for lower gum concentrations. Aspartame addition did not affect the compression parameters.     

Impact of Commercial Precooking of Common Bean (Phaseolus vulgaris) on the Generation of Peptides,After Pepsin–Pancreatin Hydrolysis,Capable to Inhibit Dipeptidyl Peptidase‐IV

The objective of this research was to determine the bioactive properties of the released peptides from commercially available precook common beans (Phaseolus vulgaris). Bioactive properties and peptide profiles were evaluated in protein hydrolysates of raw and commercially precooked common beans. Five varieties (Black, Pinto, Red, Navy, and Great Northern) were selected for protein extraction, protein and peptide molecular mass profiles, and peptide sequences. Potential bioactivities of hydrolysates, including antioxidant capacity and inhibition of α‐amylase, α‐glucosidase, dipeptidyl peptidase‐IV (DPP‐IV), and angiotensin converting enzyme I (ACE) were analyzed after digestion with pepsin/pancreatin. Hydrolysates from Navy beans were the most potent inhibitors of DPP‐IV with no statistical differences between precooked and raw (IC₅₀ = 0.093 and 0.095 mg protein/mL, respectively). α‐Amylase inhibition was higher for raw Red, Navy and Great Northern beans (36%, 31%, 27% relative to acarbose (rel ac)/mg protein, respectively). α‐Glucosidase inhibition among all bean hydrolysates did not show significant differences; however, inhibition values were above 40% rel ac/mg protein. IC₅₀ values for ACE were not significantly different among all bean hydrolysates (range 0.20 to 0.34 mg protein/mL), except for Red bean that presented higher IC₅₀ values. Peptide molecular mass profile ranged from 500 to 3000 Da. A total of 11 and 17 biologically active peptide sequences were identified in raw and precooked beans, respectively. Peptide sequences YAGGS and YAAGS from raw Great Northern and precooked Pinto showed similar amino acid sequences and same potential ACE inhibition activity. Processing did not affect the bioactive properties of released peptides from precooked beans. Commercially precooked beans could contribute to the intake of bioactive peptides and promote health.