Role of sulfites and 4-hexylresorcinol in microbial growth and melanosis prevention of deepwater pink shrimp (Parapenaeus longirostris) using a controlled atmosphere

A controlled atmosphere containing 48% CO2 and 7% O2 was used in association with refrigeration for storage of deepwater pink shrimp (Parapenaeus longirostris). Shrimp were treated with two different concentrations of sodium metabisulfite or 4-hexylresorcinol and subjected to the controlled atmosphere immediately after capture onboard ship or on arrival in port. Total volatile basic nitrogen, total viable counts, enterobacteria, lactic acid bacteria, and luminescent bacteria were determined, and black spot progression was evaluated. The combined effect of controlled atmosphere and melanosis inhibitors was used to delay black spot development as compared to the shrimp stored in ice alone. Storage under the controlled atmosphere without ice limited microbiological quality, namely, total viable counts, but enterobacterial growth was lower.Peer Reviewe

La construcción mediática de la comunidad política: la prensa en la transición española a la democracia

El artículo analiza el comportamiento y las actitudes adoptadas por la prensa española durante el primer periodo de la transición a la democracia (noviembre de 1975-diciembre de 1978), momento en el que se realizaron los cambios políticos e institucionales más relevantes del proceso. Desde diversas perspectivas se explica el papel que jugaron los principales periódicos, así como las razones que les llevaron al consenso en los temas fundamentales de discusión pública. De esta forma, se constata cómo los medios de comunicación colaboraron de forma decisiva en la construcción de una nueva comunidad política democrática. A través de varios ejemplos de diarios, tomados uno por uno y en conjunto, se explican las especiales características de este interesante caso de colaboración entre poder político y periodismo, incluyendo algunas excepciones como la prensa de extrema derecha y los sectores nacionalistas vascos

El problema termoelástico de conducción de calor entre sólidos en contacto mediante ecuaciones integrales de contorno

Se presenta una formulación basada en integrales de contorno para el análisis de problemas de contacto sin fricción en termoelasticidad bidimensional. Como modelo de resistencia térmica en la zona de contacto se consideran funciones decrecientes con la presión de contacto. Las ecuaciones del problema de conducción estacionaria de calor y las ecuaciones elásticas, que están acopladas a través de la resistencia térmica, se resuelven independientemente dentro de un proceso iterativo. La convergencia se alcanza cuando se obtiene una solución del problema elástico con deformaciones térmicas sin tracciones en la zona de contacto y con una ley de compresiones que implique valores de la resistencia concordantes con los supuestos en las ecuaciones térmicas, las cuales se resuelven en primer lugar. La formulación numérica propuesta permite detectar la posible separación de los cuerpos cuando el flujo de calor circula hacia el sólido de mayor distorsionabilidad termoelástica. El artículo incluye dos ejemplos que ilustran la aplicabilidad del procedimiento expuesto.A boundary integral formulation for two dimensional thermoelastic contact problems without friction is presented. The local thermal resistance at the contact zone is modelied as a given decreasing function of the contact pressure. The stationary heat conduction equations and the elastic equations, which are coupled through the thermal resistance, are solved independently in the scope of an iterative process. The elastic problem involving thermal loading is solved, and convergence is reached when the obtained contact pressure leads to a thermal resistance in agreement with the one assumed in the thermal problem, which was formerly solved. The present formulation also accounts for the possibility of separation in the initial contact zone when the heat flows towards the body of greatest distorsivity. The paper includes two examples illustrating the reliability of the method.Peer Reviewe

Melanosis inhibition and SO2 residual levels in shrimps (Parapenaeus longirostris) after different sulfite-based treatments

The effectiveness of different sulfite-based treatments to prevent melanosis in fresh deepwater pink shrimp (Parapenaeus longirostris) was evaluated. Increasing the concentration of sulfites, different methods of application (immersion and dust) and synergy with other compounds, such as citric acid and chelants, were investigated. The level of SO2 residues in the muscle was determined in a selection of the most effective treatments. One-hour dip treatment with 50 g kg-1 sulfite, together with citric acid and chelants, was effective for melanosis prevention for at least one week. With this treatment, the statutory limit of 0.3 g kg -1 SO2 in edible part was not exceeded by the majority of samples analysed. © 2005 Society of Chemical Industry.Peer Reviewe

The Wear Responses of the Welded Joints of ASTM A335 Gr. P11 Steels Affected by Accelerated Flow Corrosion

[Abstract] This study shows the efects of wear on welded joints of ASTM A355 Gr. P11 “Seamless Ferritic Alloy-Steel Pipe for High Temperature Service” steels subjected to the welding procedures established by codes B31.1 and ASME III. The standard welding procedure establishes the following steps: a preheating process, welding and post-weld heat treatment. This generates a wear behavior that depends on the thermal cycles to which the diferent areas of the joint are subjected. The objective of this article was the study of the behavior against the flow-accelerated corrosion of the welded joints of a low alloy steel. There is the possibility of establishing welding procedures other than those established, while maintaining the safety ranges, depending on the field of application for the steel

Functional and bioactive properties of collagen and gelatin from alternative sources: A review

The rising interest in the valorisation of industrial by-products is one of the main reasons why exploring different species and optimizing the extracting conditions of collagen and gelatin has attracted the attention of researchers in the last decade. The most abundant sources of gelatin are pig skin, bovine hide and, pork and cattle bones, however, the industrial use of collagen or gelatin obtained from non-mammalian species is growing in importance. The classical food, photographic, cosmetic and pharmaceutical application of gelatin is based mainly on its gel-forming properties. Recently, and especially in the food industry, an increasing number of new applications have been found for gelatin in products such as emulsifiers, foaming agents, colloid stabilizers, biodegradable film-forming materials and micro-encapsulating agents, in line with the growing trend to replace synthetic agents with more natural ones. In the last decade, a large number of studies have dealt with the enzymatic hydrolysis of collagen or gelatin for the production of bioactive peptides. Besides exploring diverse types of bioactivities, of an antimicrobial, antioxidant or antihypertensive nature, studies have also focused on the effect of oral intake in both animal and human models, revealing the excellent absorption and metabolism of Hyp-containing peptides. The present work is a compilation of recent information on collagen and gelatin extraction from new sources, as well as new processing conditions and potential novel or improved applications, many of which are largely based on induced cross-linking, blending with other biopolymers or enzymatic hydrolysis. © 2011 Elsevier Ltd.Peer Reviewe

Effects of gelatin origin, bovine-hide and tuna-skin, on the properties of compound gelatin-chitosan films

With the purpose to improve the physico-chemical performance of plain gelatin and chitosan films, compound gelatin-chitosan films were prepared. The effect of the gelatin origin (commercial bovine-hide gelatin and laboratory-made tuna-skin gelatin) on the physico-chemical properties of films was studied. The dynamic viscoelastic properties (elastic modulus G', viscous modulus, G″ and phase angle) of the film-forming solutions upon cooling and subsequent heating revealed that the interactions between gelatin and chitosan were stronger in the blends made with tuna-skin gelatin than in the blends made with bovine-hide gelatin. As a result, the fish gelatin-chitosan films were more water resistant (∼18% water solubility for tuna vs 30% for bovine) and more deformable (∼68% breaking deformation for tuna vs 11% for bovine) than the bovine gelatin-chitosan films. The breaking strength of gelatin-chitosan films, whatever the gelatin origin, was higher than that of plain gelatin films. Bovine gelatin-chitosan films showed a significant lower water vapour permeability (WVP) than the corresponding plain films, whereas tuna gelatin-chitosan ones were only significantly less permeable than plain chitosan film. Complex gelatin-chitosan films behaved at room temperature as rubbery semicrystalline materials. In spite of gelatin-chitosan interactions, all the chitosan-containing films exhibited antimicrobial activity against Staphylococcus aureus, a relevant food poisoning. Mixing gelatin and chitosan may be a means to improve the physico-chemical performance of gelatin and chitosan plain films, especially when using fish gelatin, without altering the antimicrobial properties. © 2011 Elsevier Ltd.Peer Reviewe

Functional and bioactive properties of collagen and gelatin from alternative sources: A review

The rising interest in the valorisation of industrial by-products is one of the main reasons why exploring different species and optimizing the extracting conditions of collagen and gelatin has attracted the attention of researchers in the last decade. The most abundant sources of gelatin are pig skin, bovine hide and, pork and cattle bones, however, the industrial use of collagen or gelatin obtained from non-mammalian species is growing in importance. The classical food, photographic, cosmetic and pharmaceutical application of gelatin is based mainly on its gel-forming properties. Recently, and especially in the food industry, an increasing number of new applications have been found for gelatin in products such as emulsifiers, foaming agents, colloid stabilizers, biodegradable film-forming materials and micro-encapsulating agents, in line with the growing trend to replace synthetic agents with more natural ones. In the last decade, a large number of studies have dealt with the enzymatic hydrolysis of collagen or gelatin for the production of bioactive peptides. Besides exploring diverse types of bioactivities, of an antimicrobial, antioxidant or antihypertensive nature, studies have also focused on the effect of oral intake in both animal and human models, revealing the excellent absorption and metabolism of Hyp-containing peptides. The present work is a compilation of recent information on collagen and gelatin extraction from new sources, as well as new processing conditions and potential novel or improved applications, many of which are largely based on induced cross-linking, blending with other biopolymers or enzymatic hydrolysis. © 2011 Elsevier Ltd.Peer Reviewe

Quality of thawed deepwater pink shrimp (Parapenaeus longirostris) treated with melanosis-inhibiting formulations during chilled storage

This work investigates how the treatment of thawed deepwater pink shrimp (Parapenaeus longirostris) with several melanosis-inhibiting formulations, affects the quality of the shrimp during chilled storage. Formulations were as follows: a formulation containing 4-hexylresorcinol (0.1 and 0.05%), in combination with organic acids and chelating agents, a commercial formula based on sulphites, and a mixture of gluconic acid and commercial sulphites. No noticeable differences were observed for both trimethylamine and total volatile bases during chilled storage. pH evolution was irrespective of the treatment condition. Microbial load enlarged after the sixth day of chilled storage. Higher total bacteria counts were associated with the control and sulphite treatment conditions, while lactic acid bacteria growth seemed to be favoured under formulations based on 4-hexylresorcinol. The appearance of melanosis occurred more rapidly in control shrimp or in shrimp treated with commercial sulphites. 4-hexylresorcinol formulations preserved the quality of thawed shrimp and could replace traditional sulphites. © 2007 The Authors. Journal compilation 2007 Institute of Food Science and Technology Trust Fund.Peer Reviewe