Improvement of dough rheology, bread quality and bread shelf-life by enzymes combination

12 pages, 2 figures, 6 tables.-- Published online 28 November 2006.Present work seeks to systematically analyse the individual and synergistic effects of some gluten-crosslinking enzymes (transglutaminase, glucose oxidase and laccase), along with polysaccharide and gluten degrading enzymes (alpha-amylase, xylanase and protease), in breadmaking systems. Except glucose oxidase (GO) and laccase (LAC), enzymes affected significantly to viscoelastic properties of dough. Results confirmed the strengthening effect exerted by transglutaminase (TG). However, alpha-amylase (AMYL), xylanase (XYL) and protease (PROT) promoted a similar decrease in all dynamic moduli analysed, particularly after 180 min of incubation. Addition of XYL to TG containing samples showed to be an interesting alternative to prevent excessive dough strengthening. Bread quality parameters were significantly affected by individual enzyme addition, except when LAC was used. TG diminished loaf specific volume and provided a finer crumb structure. Polysaccharide degrading enzymes and PROT led to better shape, greater specific volume and void fraction of loaves. Significant interactions between TG and all the other enzymes except GO, were proved. According to crumb texture evolution during storage, bread staling increased with TG addition, whilst AMYL, XYL and PROT exhibited a significant antistaling effect.This work was financially supported by Comisión Interministerial de Ciencia y Tecnología Projects (MCYT, AGL2002-04093-C03ALI and AGL2005-05192-C04), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Valladolid, Spain.Peer reviewe

Acquiring the notion of learning hypotheses in mathematics teacher education

The notion of hypothetical learning trajectory has generated much interest among experts in mathematics education. It is proposed that this notion is a useful tool in teachers’ teaching practice and that it is necessary to prepare teachers in their capacity to formulate hypothetical learning trajectories about specific mathematics school topics. It is therefore also necessary to explore the learning processes that teachers undergo when learning this notion in their education. In this article, we introduce the notion of learning hypotheses as an adaptation of the idea of hypothetical learning trajectory (SIMON, 1995). We describe how the groups of secondary-school mathematics teachers that participated in a teacher education program understood and used this notion in order to determine the contribution of a set of tasks to a learning goal previously established. We found that the groups developed their knowledge of the notion of learning hypotheses and used it in a heterogeneous way, and that the education program was partly successful in its goal to make the groups of teachers learn and perceive the notion’s utility

Aprendizaje basado en juegos

Gracias al incremento de potencia de los ordenadores, gran cantidad de personas dedican horas y horas a aprovechar su aspecto más lúdico, los videojuegos. Por otro lado, existen programas educativos que aprovechan la infinita paciencia de los ordenadores que les hacen capaces de explicar conceptos una y otra vez hasta que los alumnos lo entiendan. En este artículo mostramos qué cosas pueden aportar las aplicaciones de enseñanza a los videojuegos y viceversa. Terminamos describiendo JV2M, como un ejemplo de sistema de aprendizaje basado en juegos

Development of expression vectors based on pepino mosaic virus

<p>Abstract</p> <p>Background</p> <p>Plant viruses are useful expression vectors because they can mount systemic infections allowing large amounts of recombinant protein to be produced rapidly in differentiated plant tissues. Pepino mosaic virus (PepMV) (genus <it>Potexvirus</it>, family <it>Flexiviridae</it>), a widespread plant virus, is a promising candidate expression vector for plants because of its high level of accumulation in its hosts and the absence of severe infection symptoms. We report here the construction of a stable and efficient expression vector for plants based on PepMV.</p> <p>Results</p> <p>Agroinfectious clones were produced from two different PepMV genotypes (European and Chilean), and these were able to initiate typical PepMV infections. We explored several strategies for vector development including coat protein (CP) replacement, duplication of the CP subgenomic promoter (SGP) and the creation of a fusion protein using the foot-and-mouth disease virus (FMDV) 2A catalytic peptide. We found that CP replacement vectors were unable to move systemically and that vectors with duplicated SGPs (even heterologous SGPs) suffered from significant transgene instability. The fusion protein incorporating the FMDV 2A catalytic peptide gave by far the best results, maintaining stability through serial passages and allowing the accumulation of GFP to 0.2-0.4 g per kg of leaf tissue. The possible use of PepMV as a virus-induced gene silencing vector to study gene function was also demonstrated. Protocols for the use of this vector are described.</p> <p>Conclusions</p> <p>A stable PepMV vector was generated by expressing the transgene as a CP fusion using the sequence encoding the foot-and-mouth disease virus (FMDV) 2A catalytic peptide to separate them. We have generated a novel tool for the expression of recombinant proteins in plants and for the functional analysis of virus and plant genes. Our experiments have also highlighted virus requirements for replication in single cells as well as intercellular and long-distance movement.</p

REFLEXIÓN SOBRE LA VIVIENDA DE INTERÉS SOCIAL PARA LA COMUNIDAD WAYÚU

En este artículo se hace una reflexión sobre la solución de vivienda para la comunidad Wayuu, población de bajos recursos asentada en la Guajira colombiana. Así, se ha identificado un problema que tiene implicaciones más profundas que el simple hecho de proponer proyectos urbanos y arquitectónicos, pues las diferentes alternativas técnicas y económicas que tienden a bajar costos van en detrimento de la calidad física, de las condiciones de habitabilidad e incluso del ser social, sin dejar a un lado la dependencia de los largos y costosos créditos. Sin duda una situación crítica que podría contrastarse si se trabaja para propiciar el desarrollo de las comunidades, a través de una explotación positiva y sostenible de la riqueza territorial del país, mediante trabajos estables y salarios dignos que generen una autonomía social para la solución de sus problemas. Seguidamente, se incluyen además las propuestas de diseño de tres grupos de estudiantes de la Facultad de Arquitectura de la Universidad Santo Tomás de Bucaramanga, presentadas en el concurso Internacional CONVIVE VI, convocado por la revista ESCALA con motivo de su versión dedicada al territorio de la comunidad Wayuu, y de las cuales una mereció la primera mención por parte del jurado.ABSTRACTThis article reflects on the housing solution for the Wayuu community, low income population settled in the Colombian Guajira, up north the country. Thus, it is identified a problem that has deeper implications than a simple proposal of urban and architectural projects, since the different technical and economic alternatives that tend to reduce costs drive against the physical quality of living conditions and even of social being, as well as the dependence on the long and overpriced loans. Certainly, a critical situation that could be contrasted by promoting effectively the development of communities, across a positive and sustainable exploitation of the territorial wealth of the country, supported with stable jobs and decent wages that generate social autonomy to solve their problems. Then, the article also include the projects of three students groups from the Faculty of Architecture at the University of Santo Tomas de Bucaramanga, presented at the International Competition CONVIVE VI which was organized by the magazine ESCALA on his version dedicated to the territory of the Wayuu people. One of these proposals won the Jury’s First Mention

Rasgos sedimentarios indicadores de inestabilidad causada por actividad tectónica sismogenética : las cuencas neógenas de las Minas de Hellín y Cenajo (Prebético externo, SE de España)

Resum