Quality Enhancement of Chilled Lean Fish by Previous Active Dipping in <Emphasis Type="Italic">Bifurcaria bifurcata</Emphasis> Alga Extract

The present study addressed the quality enhancement of chilled fish by applying a preliminary dipping treatment containing a bioactive extract of the alga Bifurcaria bifurcata. Megrim (Lepidorhombus whiffiagonis) specimens were dipped in ethanolic–aqueous solutions containing two different concentrations of the alga extract (high: HAC batch and low: LAC batch). Two types of control batch were considered (ethanol–water dipping and no dipping). Microbial, chemical and sensory qualities were monitored in fish throughout a 13-day storage period. An inhibitory effect (p?<?0.05) of the dipping treatment (washing and the presence of alga extract) on microbial activity was observed, as determined by microbial (Enterobacteriaceae, lipolytic bacteria and psychrotrophs) and chemical (trimethylamine and free fatty acid formation) analyses. In most cases, this effect was found to be more intense for prolonged storage times and in fish specimens corresponding to the HAC batch. However, the combined effect of washing and the inclusion of alga extract in the dipping medium did not affect (p?>?0.05) the rate of lipid oxidation events during storage. Interestingly, average scores revealed increased sensory quality in megrim corresponding to the HAC batch for prolonged storage (9–13 days). Consequently, the use of a bioactive extract of B. bifurcata alga as a preliminary dipping treatment can be considered of interest for further fish storage due to both its simplicity and beneficial effects on fish quality enhancement.     

Foaming characteristics of β-lactoglobulin as affected by enzymatic hydrolysis and polysaccharide addition: Relationships with the bulk and interfacial properties

The objective of this work was to study the effect of enzymatic hydrolysis and polysaccharide addition on the foaming characteristics of β-lactoglobulin (β-LG). Enzymatic treatment was performed in the hydrolysis degree (HD) range of 0.0–5.0% using bovine α-chymotrypsin II immobilized on agarose microbeads. Anionic non-surface active polysaccharides (PS), sodium alginate (SA) and λ-carrageenan (λ-C) were studied in the concentration range of 0.0–0.5 wt.%. Foaming characteristics were determined by conductimetric and optical methods and were linked to protein diffusion kinetics, film mechanical properties and biopolymer molecular dynamics in solution. Experiments were performed at constant temperature (20 °C), pH 7 and ionic strength 0.05 M. Limited hydrolysis improved the formation and stability of β-LG foam possibly due to an increased protein diffusion rate and film dilatational elasticity. Furthermore, PS addition caused different effects on β-LG foaming characteristics depending on the PS type, their relative concentration and extent of enzymatic treatment (HD). Diffusion rate and interfacial rheological behavior of mixed systems could exert a decisive role in foaming characteristics of β-LG and its hydrolysates in close connection with biopolymer interactions in solution, e.g., macromolecule repulsion, protein segregation/aggregation and soluble complexes formation.     

Dry gas operation of proton exchange membrane fuel cells with parallel channels: Non-porous versus porous plates

We present a study of proton exchange membrane (PEM) fuel cells with parallel channel flow fields for the cathode, dry inlet gases, and ambient pressure at the outlets. The study compares the performance of two designs: a standard, non-porous graphite cathode plate design and a porous hydrophilic carbon plate version. The experimental study of the non-porous plate is a control case and highlights the significant challenges of operation with dry gases and non-porous, parallel channel cathodes. These challenges include significant transients in power density and severe performance loss due to flooding and electrolyte dry-out. Our experimental study shows that the porous plate yields significant improvements in performance and robustness of operation. We hypothesize that the porous plate distributes water throughout the cell area by capillary action; including pumping water upstream to normally dry inlet regions. The porous plate reduces membrane resistance and air pressure drop. Further, IR-free polarization curves confirm operation free of flooding. With an air stoichiometric ratio of 1.3, we obtain a maximum power density of 0.40 W cm⁻², which is 3.5 times greater than that achieved with the non-porous plate at the same operating condition.     

Physicochemical profile and determination of volatile compounds in cachaça stored in new oak (Quercus sp.), amburana (Amburana cearensis), jatoba (Hymenaeae carbouril), balsam (Myroxylon peruiferum) and peroba (Paratecoma peroba) casks by SPME‐GC–MS

Aging has become common practice among producers seeking to increase the value of their products. The objective of this work was to conduct periodic monitoring by solid‐phase microextraction–gas chromatography–mass spectrometry of the physical and chemical quality of aging cachaça in terms of the alcohol content, volatile acidity, esters, aldehydes, higher alcohols, furfural, methanol, dry extract, copper and volatile compounds in the production process (distilled fractions) and during storage in casks newly made from oak (Quercus sp.), amburana (Amburana cearensis), jatoba (Hymenaeae carbouril), balsam (Myroxylon peruiferum) and peroba (Paratecoma peroba). The barrels were made in a specialized cooperage, and cachaça was obtained from a production unit in the southern region of Minas Gerais. Distinct physicochemical values were obtained for the distilled fractions; head and tail fractions had inappropriate concentrations of alcohol, aldehydes and butan‐1‐ol. Values within the limits established by law were obtained for the heart fraction, both in the distillation process and during aging, and it is, therefore, suitable for consumption. Several important compounds responsible for the aroma and flavour of the cachaças were observed, and alcohols, acids, esters and sesquiterpenes were found to compose the main groups. Through variance and main component analysis, important chemical changes were observed in the beverages. Copyright © 2016 The Institute of Brewing & Distilling     

Inactivation of Escherichia coli O157:H7 in fruit juices by combined treatments of citrus fruit essential oils and heat

This work approaches the possibility of combining mild heat treatments with citrus fruit essential oils (EOs) to improve the effectiveness of heat treatments and thus to reduce treatment intensity. Concentrations between 10 and 200μL/L of lemon, mandarin, or orange EO were tested at 54°C for 10min in laboratory media, determining that 200μL/L of each EO was necessary to achieve a 5 log(10) reduction of the initial Escherichia coli O157:H7 concentration. A relationship could be established between sublethally injured cells after the heat treatment and inactivated cells after the combined process. In apple juice, the synergism in the inactivation of E. coli O157:H7 when adding 200μL/L of lemon EO might suppose a reduction in the treatment temperature (of 4.5°C) or in the treatment time (by 5.7 times) within the range of temperature assayed (54-60°C). Addition of 75μL/L of lemon EO was determined to achieve the same synergistic effect of the combined treatment when the initial inoculum was reduced from 3×10(7) to 3×10(4)CFU/mL. Since the addition of lemon EO did not decrease the hedonic acceptability of apple juice, the proposed combined treatment could be further studied and optimized for the production of new minimally processed juices.     

Role of an autochthonous starter culture and the protease EPg222 on the sensory and safety properties of a traditional Iberian dry-fermented sausage "salchichón"

The effect of the addition of an autochthonous starter culture and the protease EPg222 on the physico-chemical and sensory characteristics of dry-fermented sausage ‘‘salchichon” was investigated. Sausages were prepared with purified EPg222 and Pediococcus acidilactici MS200 and Staphylococcus vitulus RS34 as starter culture (P200S34), separately and together, ripened for 90 days, and compared with a control batch. Dry-fermented sausages ripened with EPg222 and starter culture showed higher amounts of AN and volatile compounds derived from amino acid catabolism than the control, especially in samples in which was added the association of enzyme and starter culture (P200S34 + EPg222). There were clear differences shown by the texture analysis, with the P200S34 + EPg222 batch being less hard. Especially important was the result found in biogenic amines, since the association P200S34 + EPg222 reduced their accumulation compared to the EPg222 batch. The use of EPg222 may be of great interest to improve the sensory characteristics of dry-fermented sausages, but its association with the selected starter culture with low decarboxylase activity is necessary to guarantee healthiness and homogeneity.     

Toughening strategies of carbon nanotube/polycarbonate composites with electromagnetic interference shielding properties

The effect of different toughening strategies on the mechanical properties of multiwalled carbon nanotube/polycarbonate composite (PC/MWNT) for electromagnetic interference shielding was analyzed from the mechanical and fracture tests using linear elastic fracture mechanics. The effect of processing (injection and compression molding) and manufacturing (annealing) conditions in the mechanical properties and electrical conductivity has been studied. The classic electromagnetic theory predicts a shielding effectiveness around 40 dB for nanocomposites with 5 wt% of MWNT in the frequency range studied. These values make these compounds to be very interesting materials for potential applications as electronic housings. Therefore, a combination of cyclic form of polybutylene terephthalate addition and annealing strategies let to optimize flexural parameters and improve the flexural modulus of PC composites. The rheology results showed that the dynamic moduli and the viscosity grew with increasing MWNT content. A significant change in frequency dependence of the moduli was observed, with respect to pure PC, which indicates a transition from a liquid‐like to a solid‐like behavior. Finally, the morphological study proves that the composites display different toughening mechanisms as function of carbon nanotube quantity. This fact could explain the different fracture behaviors of materials. In summary, it has been proved that it is possible to obtain PC/MWNT nanocomposites with relatively high conductivity, minimizing the loss of mechanical properties, using processing techniques easily scalable at industrial level. POLYM. COMPOS., 34:1938–1949, 2013. © 2013 Society of Plastics Engineers     

Statistical parameters of the indicating surface of natural reflectance for biaxial transparent media

Abstract

The optical properties are an important characteristic of a mineral. These properties can be studied with a photometer microscope using the indicating surface of natural reflectance (ISRN). Transparent uniaxial media have been studied. Biaxial transparent media, in the same way as uniaxial media, can be analysed by knowing the statistical parameters of the ISRN. To analyse these media, we need the expressions that relate these parameters to the refractive index of the incident medium and to the principal indices of the medium under observation.     

Stress analysis in bone tissue around single implants with different diameters and veneering materials: A 3-D finite element study

The aim of this study was to evaluate the stress distribution on bone tissue with a single prosthesis supported by implants of large and conventional diameter and presenting different veneering materials using the 3-D finite element method. Sixteen models were fabricated to reproduce a bone block with implants, using two diameters (3.75 × 10 mm and 5.00 × 10 mm), four different veneering materials (composite resin, acrylic resin, porcelain, and NiCr crown), and two loads (axial (200 N) and oblique (100 N)). For data analysis, the maximum principal stress and von Mises criterion were used. For the axial load, the cortical bone in all models did not exhibit significant differences, and the trabecular bone presented higher tensile stress with reduced implant diameter. For the oblique load, the cortical bone presented a significant increase in tensile stress on the same side as the loading for smaller implant diameters. The trabecular bone showed a similar but more discreet trend. There was no difference in bone tissue with different veneering materials. The veneering material did not influence the stress distribution in the supporting tissues of single implant-supported prostheses. The large-diameter implants improved the transference of occlusal loads to bone tissue and decreased stress mainly under oblique loads. Oblique loading was more detrimental to distribution stresses than axial loading.