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The influence of casein hydrolysates (CHs) and yeast on the viscoelasticity of wheat dough at 25 °C were analysed. Three wheat doughs were studied: the unyeasted dough (UYD), the unyeasted dough with CHs (UYD-C) and the yeasted dough (YD). The characteristic parameters in the linear viscoelastic range (LVER) were analysed by stress sweep at 6.3 rad/s: UYD-C dough exhibited higher values of stress (σmax) and strain (γmax) amplitudes, and softer gel network (lower complex modulus, G*) comparing with UYD dough. The oscillatory data suggest that CHs would work as (energy and time) stabilising-agents based on the greatest reticular energy (E parameter) and the lowest frequency dependence of phase angle (δ) at the low frequency range. The rotatory tests show that CHs may act as shear thinning agents in the gluten-starch network, facilitating the solid-fluid transition at the yield point (UYD-C dough). The yeasted dough (YD) exhibited a more shear sensitive structure, evidenced in the highest influence of frequency on the elastic (G′) and viscous (G″) parameters, and gel to sol transition at 0.23 rad/s was observed.

Dactylopius coccus es un insecto de importancia comercial como fuente de un colorante natural denominado ácido carmínico. Para su producción comercial en cautiverio, se ha promovido la cría en cladodios suspendidos a diferentes alturas, en un sistema denominado “nopaloteca”. Sin embargo, se desconoce si su calidad y rendimiento es uniforme en los diferentes niveles. El objetivo de este estudio fue determinar la influencia de la altura del nivel en una “nopaloteca” y el índice de cosecha en la concentración de ácido carmínico (CAC, %) y peso fresco (PF, g) de D. coccus. La crianza del insecto se realizó en una “nopaloteca” de madera (3x3 m), con cuatro niveles de altura (0.5, 1.0, 1.50 y 2 m). Durante el ciclo de cultivo se registró cada día la temperatura, la humedad relativa y la intensidad luminosa. Las hembras adultas se recolectaron en dos etapas del desarrollo: pre y postoviposición. La CAC más alta (19.2%) se obtuvo en 1.0 m de altura, aunque este nivel registró el PF más bajo con 3.5 g por cladodio, que expresa una correlación negativa entre la CAC y el PF. La recolecta en postoviposición generó una CAC superior (18.8%), aunque el PF se redujo. Tanto la humedad relativa (HR) como la iluminación total, pero principalmente la temperatura que incidió en cada nivel, influyeron en la calidad y el rendimiento de D. coccus, aunque de manera diferencial sobre ambos factores, lo cual indica la presencia de límites óptimos de desarrollo. Bajo las condiciones del estudio, el sistema de cría en “nopaloteca” produjo en promedio 4.5 g de cochinilla por cladodio y una CAC de 17.5%. Los niveles evaluados causaron diferencias en rendimiento y calidad, pero sus valores más altos se registraron en los niveles intermedios (1.0 y 1.5 m). El índice de cosecha recomendado para obtener mayor CAC fue la etapa de postoviposición.

In the studied commercial pea protein isolate (PPI) some physicochemical modifications are induced in the protein structure during its processing. That fact would result into a reduction of proteins techno-functional properties. It has been evidenced by Differential Scanning Calorimetry the protein denaturation what gives as a result poor gelling ability. Microbial transglutaminase (MTGase) was added at different concentrations to improve the gelation process at two different settings/thermal treatments to make suitable texture PPI gels as a base for various meat and/or seafood analogues. SDS-PAGE analysis indicated that MTGase activity was focused on the polymerization of vicilins and legumins resulting in the promotion of new intermolecular protein complexes (increase in β-sheet aggregates). Rheological data showed that at 23% PPI with 5 and 7 U/g protein of MTGase the gel strength increased in terms of breaking force and complex modulus. It also improved the conformational stability and flexibility of their gel networks. The results suggest that appropriate gels with 23% PPI could be obtained adding 5 U/g MTGase able to be used as meat and/or seafood analogues., This work was supported by the Spanish Ministry of Economy and Competitiveness (RTA2015-00003-CO2-02).

Gelling ability of a bean protein isolate (BPI) obtained from a naturally low-lectin variety (Phaseolus vulgaris var. Almonga) was analysed. For that purpose differences on gels processing: concentration (14% and 17%), salt addition (0 and 2%), and pH (6.5 –lot A- and 7 –lot B), were studied to obtain suitable colour, mechanical and viscoelastic properties for making appropriate meat and seafood analogues. Gelation at pH 7 at both 14 and 17% BPI concentrations, produced less rigid, more flexible, time-stable and cohesive gel networks. Colour of the resulting gels was white enough to be considered as an adequate base for making plant-based analogues. The content of total galactoside, inositol phosphates and trypsin inhibitors (bioactive compounds) present in one serving (100 g) of these BPI gels were up to 0.80 mg/g, 8.06 mg/g and 239 TIUs, respectively., This work was supported by the Spanish Ministry of Economy and Competitiveness (RTA2015-00003-CO2)., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.

The functional properties α-LA nanotubes and the gels formed during their synthesis were studied to evaluate their potential applications. The bioactivity of α-LA was improved by the synthesis of nanotubes, with significantly (p < 0.05) higher ACE-inhibitory (IACE) and antioxidant activity (μmol TE/mg protein). The IC50 (protein concentration to inhibit 50% of ACE activity) of α-LA nanotubes was 281 ± 21 μg mL−1 and the antioxidant activity 1.28 ± 0.01 μmol TE mg−1 protein. Besides, the IACE-value was significantly higher (p < 0.05) when the α-LA fragments incorporated into the nanotube’ structure were considered, and not only the low MW peptides formed during the nanotube synthesis (not incorporated into the nanotube’ structure).This study also analysed how different ion ratios in the synthesis of α-LA nanotubes changed their functionality. Thus, gels formed by long and regular α-LA nanotubes (2 mol of Mn2+/mol of α-LA) showed fluid−gel characteristics, with some time-dependent shear-thinning flow (thixotropy). At fixed recovery time, a less thixotropic behaviour was found in these fluid gels (high percentage −71.6 ± 7.4%− of structural regeneration). Additionally, they stayed in gel form at high temperatures and even increased their stiffness up to 65 °C. The increase in the ion ratio (3 mol of Mn2+/mol of α-LA) during nanotube synthesis modified the α-LA nanotubes' microstructure nanotubes resulting in short and branched nanotubes. These gels showed a higher level of pseudo-plasticity, higher consistency and thixotropy. These are characteristics of a more complex and dense network with greater time dependence and lower structural regeneration (18.6 ± 2.0%) Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Xunta de Galicia | Ref. ED431E 2018/07

Recently, legume protein isolates are increasingly of interest as ingredients for the food industry; however, in spite of their health benefits, there is a limited information about the presence of bioactive compounds in the protein isolates. The objective of this study was to establish the phytochemical composition and selected techno-functional properties of pea and bean flours and their protein isolates obtained applying different drying methods. Regarding proximate composition, bean flour contained higher amounts of total protein (23%) and fat (44%) than pea flour; bean protein isolate (BPI) contained higher total and soluble protein, fat and starch than the pea protein isolate (PPI). Both protein isolates showed a similar emulsifying capacity (around 27%). Emulsion stability and foaming capacity were higher in the PPI (around 36%). Bean flour contained lower amounts of α-galactosides (31.64 mg/g) but a higher trypsin inhibitors content (21.95 TIU/mg) than pea flour. The preparation procedure of the protein isolates affected the bioactive compound content. The PPI showed a reduction of inositol phosphates (13%), galactosides (76%), trypsin inhibitors (90%) and total phenolic compounds (35%) compared to its whole flour. The BPI contained higher amounts of inositol phosphates (137%) and total phenolic compounds (135%) than its flour, while it showed a lower content of galactosides (54%) and a similar amount of trypsin inhibitors. Thus, the bioactive compound content and the functional properties studied indicate that protein isolates can be used as ingredients with added-value in the development of new formulated food products, allowing their increasing use in the food industry., The Spanish Ministry of Economy and Competitiveness funded this work (RTA2015-00003-C02).

[ES] Se han establecido grupos de trabajo multidisciplina-res para desarrollar videojuegos que han implicado a dos asignaturas de la Facultad de BB.AA. y a otras dos de la Escuela de Ingeniería Informática. Los equipos han seguido la misma metodología que se sigue en las empresas de desarrollo de videojuegos. Han utilizado aplicaciones en línea para editar los documentos de diseño de forma colaborativa, compartido código y otros documentos mediante GitHub, se han coordinado empleando redes sociales, han empleado herramientas de autor y de programación de última generación, junto con entornos profesionales de desarrollo de videojuegos. Se han empleado metodologías ágiles para el desarrollo de videojuegos y se han mantenido reuniones de control del progreso a lo largo de todo el cuatrimestre. A pesar de que muchos alumnos no habían recibido docencia previa en videojuegos ni en la herramienta empleada en la asignatura, los resultados han sido muy satisfactorios. La nota media de cada especialidad ha estado cercana a los 8 puntos. Los alumnos han valorado positivamente el ritmo seguido y las sesiones de seguimiento, la metodología empleada, la libertad de elección de temas, el poder trabajar con alumnos de otras disciplinas y la calidad de los resultados., [EN] Multidisciplinary work groups have been established to develop video games involving two courses in the Faculty of Fine Arts and two courses in the Computer Science School. The teams have followed the same methodology used in the video game development industry. They have used online applications to edit design documents collaboratively. They have shared code and other documents using GitHub. They have been collaborating using social networks. They have used the latest authoring and programming tools together with professional video game development environments. Agile methodologies have been used for the development of the projects. Progress monitoring meetings have been held throughout the four-month period. Although many students had no previous experience developing video games nor using the engine studied in the course, the results have been very satisfactory. The average mark in each group has been close to 8 points. Students have positively assessed the pace followed and the follow-up sessions, the methodology used, the freedom to choose topics, working with students from other disciplines and the quality of the results.

Thermoviscoelastic and biochemical properties of Afuega'l Pitu cheese blancu (B) and roxu (R), a Spanish acid-curd cheese made from cow’s milk, were determined at 3, 15, 30 and 60 days of ripening. The contents of fat (>45 g/100 g total solids, TS) and NaCl ( viscous modulus, G''), irrespective of temperature. The best gel properties (low values of loss factor, tanδ = G''/G', and minor frequency dependence, i.e., low n', n'' exponents), were observed at 20 °C for B30 and R30. The viscoelastic parameters ( G 0 ' and G 0 ' ' ) increased with ripening time, irrespective of the temperature, and for a fixed ripening time they were lower at higher temperature. At 75 °C, all samples exhibited notable frequency dependence (n'' ≫ n'), resulting in shear-induced gelation at low frequencies (high oscillation times) which was consistent with data in thermal profiles from 70 °C to 90 °C.

Four lots of glucomannan (GM) gels (5 g/100 mL w/v): two lots of native GM gels (pH = 6.6; lot N) and two lots of deacetylated GM gels (pH = 11; lot D) were subjected to high hydrostatic pressure (HHP) at 0 (N0 and D0 respectively), and 400 MPa (N400 and D400 respectively). All samples were frozen and stored at −20 °C for two years to analyse the effect of long-term frozen storage on the viscoelastic parameters of pressurized samples according to pH (FN400, FD400) vs unpressurized samples (FN0, FD0), all in comparison with the respective unfrozen unpressurized controls (N0, D0). HHP improved the gel properties of frozen native gels as evidenced by significantly higher stress (σ) and strain (γ) amplitudes in FN400 vs FN0, albeit the effect was attenuated when GM was deacetylated (FD400 vs FD0). From T > 65 °C, HHP produced rubber-like elasticity in native GM gel (N400), and this thermal response was maintained in frozen native gel (FN400). Thermal profiles of deacetylated GM gels suggest that HHP reduced vitrification of physical networks in FD400 vs FD0., Authors wish to thank the Spanish Ministry of Economy and Competitiveness for financial support (AGL2011-24693) and Xunta de Galicia for its financial support under the consolidation and restructuring program of competitive research units.

Several weakly deacetylated glucomannan gels (pH = 9.1), at a concentration of 5 g/100 mL, were subjected to high hydrostatic pressure (HHP) at 0, 100, 200, 400 and 600 MPa. They were frozen and stored at −20 °C for two years to study the influence of long-term frozen storage on the rheological properties of pressurized samples (FP100, FP200, FP400, FP600) compared with a frozen unpressurized control (FP0) and an unfrozen unpressurized control (P0). In unpressurized gels, frozen storage reduced stress (σ) and strain (γ) amplitudes while forming a more solid-like network (FP0 vs P0). Gel FP0 maintained the rubber-like response from temperature (T) > 70 °C as in P0. HHP reduced loss of conformational stability and enhanced cohesiveness in FP100−FP600 vs FP0. Particularly, 400 MPa improved the degree of connectivity in the glucomannan (GM) network producing a better thermoset response at T > 70 °C (FP400)., Authors wish to thank the Spanish Ministry of Economy and Competitiveness for financial support (AGL2011-24693) and Xunta de Galicia for its financial support under the consolidation and restructuring program of competitive research units.

The gelling of two commercial pea protein isolates (PPI) at 20% and 23% PPI concentration, and the effect of microbial transglutaminase (-0- and -5- U/g protein), were analysed. The final aim was to get PPI gels with textural properties enough to make meat and seafood analogues. The first PPI (-A-), was made by alkaline solubilization and isoelectric precipitation from pea flour. The second one (-B-), was obtained by aqueous dispersion of the pea flour and concentration of the soluble protein. The water and oil holding capacities of PPI-A suggested a higher degree of protein denaturation which was assessed by Dynamic thermo mechanical analysis (DMTA) and Fourier transform infrared spectroscopy (FTIR). FTIR data showed lower intermolecular β-sheet aggregates in PPI-B gels than in PPI-A. This result was consistent with the reticulated and well-interconnected network from scanning electron microscopy (SEM) of PPI-B gels in line with the higher strain amplitude (γmax), and the lower loss factor (tanδ) in PPI-B gels vs PPI-A gels. The MTGase enzyme significantly improved the structural quality of the PPI-B gels (high Q-factor) at 20% and 23% PPI. For all these reasons PPI B is more suitable for achieving consistent gels as bases for meat and seafood analogues., This work was supported by the Spanish Ministry of Economy and Competitiveness (RTA2015-00003-C02).

Mixed surimi gels with 8%, 10% and 15% of pea protein isolate (PPI) were made in order to replace part of the myofibrillar proteins with PPI. Phytochemical, mechanical, viscoelastic and structural properties of heat-induced gels were analysed. Resulting gels contained low amounts of galactosides, inositol phosphates, protease inhibitors and phenolic compounds with potential specific health roles. A coupled PPI-myofibrillar matrix was produced on a basis of water binding capacity, electrophoresis profile, reticular flexibility and homogeneous microstructure. Mixed gels were less rigid (lower complex modulus -G*-) and exhibited slightly greater water binding ability than control gel. Addition of 8% and 10% PPI improved conformational flexibility, energy stability and elastic character. In mixed gels with 15% PPI the continuity of the mixed-protein matrix was disrupted and the mechanical and viscoelastic parameters deteriorated. Mixed surimi gels with 8% or 10% were thus more sustainable and healthy for use in meat or seafood analogue processing., This work was supported by the Spanish Ministry of Economy and Competitiveness (RTA2015-00003-CO2).

Afuega’l Pitu atroncau cheese, Blancu (B) and Roxu (R) varieties, were collected at 30 days of ripening from 9 farms (B1−B9 and R1−R9) to determine the biochemical and linear viscoelastic parameters, as well as the microstructure. B and R samples exhibited fused casein particles in the protein matrix with a high packing effect and different fat distribution. The lowest total solids content led to the lowest stress amplitude (σmax) and gel strength (G*). B samples exhibited higher values of strain amplitude (γmax) and σmax than R, but with a similar solid-like character (tanδ).

The objective of this study was to know the thermo-rheological behaviour of eight batches of Afuega’l Pitu cheese (F1−F8), 30 days ripened, based on its biochemical composition. Negative correlations between the moisture-to-protein ratio and the viscoelastic moduli (G′ and G′′) from dynamic thermo-mechanical analysis (20 °C−90 °C) were determined. F1–F8 had similar thermal profiles maintaining the solid-like character in the protein matrices up to 90 °C.

Most of the studies related to the susceptibility of the main bovine whey proteins to the action of cardosins of Cynara cardunculus have underestimated the potential of these proteases to hydrolyse β-Lactoglobulin (β-Lg). These works used the one-factor-at-a-time methodology, which ignores the interactions and can lead to misleading conclusions. In this work, the hydrolysis of bovine whey protein, exploiting the joint action of cardosins A and B of C. cardunculus, was optimised. For that purpose, a second-order rotatable design (with two variables at five levels) was used to study the combined effect of pH and temperature on the degree of hydrolysis (DH), the number of peptides generated and the angiotensin I-converting enzyme (ACE)-inhibitory activity. The complete hydrolysis of α-Lactalbumin (α-La) was achieved at pH 6.99/35.86 °C and pH 5.01/64.14 °C, and contrary to the previous studies, cardosins were able to hydrolyse β-Lg (up to ~40%) at pH 6.29/50 °C. In addition, the statistical analysis revealed that the same pH and temperature values that led to a minimum DH for α-La also provide a maximum DH for β-Lg. At pH 5.3 and 60 °C, we have obtained abundant peptides with high angiotensin I-converting enzyme (ACE)-inhibitory activity, but also a non-hydrolysed β-Lg. So, the purification and identification of the bioactive peptides, produced under these hydrolysis conditions, was performed. Moreover, the biotechnological potential of the β-Lg obtained was successfully proved for 3 promising applications: heat-induced gels, nanofibrils (self-assembly) and microparticles (spray-dryer).

The objective of this study was to know the relationship between biochemical parameters and viscoelastic properties at constant temperature of atroncau roxu Afuega'l Pitu cheese. Samples from the eight (R1–R8) cheese factories belonging to the PDO were submitted to analysis. The gross composition, mineral content, physicochemical parameters, and lipolysis (fat acidity) were studied. Stress sweeps (20 °C) showed that stress amplitude (σmax) ranged from 177 ± 18 Pa (R8) to 885 ± 89 Pa (R5) and complex modulus (G*) from 51 ± 3 kPa (R8) to 326 ± 43 kPa (R5). These data were influenced by the moisture-to-protein ratio (MPR), which was lowest in R5 (1.52 ± 0.02) and highest in R8 (2.61 ± 0.08). The temperature dependence of the mechanical spectra was also analysed at 20 °C, 50 °C and 75 °C. The storage (G′) and loss (G″) moduli were lowest in R8 and highest in R5, irrespective of temperature. At 50 °C, all samples exhibited an increase in loss factor (tanδ) values in the complete frequency range, whereas at 75 °C a notable solid-like reinforcement (lowest tanδ) was observed at low frequencies, indicating shear-induced gelation.

Conference proceedings of the Iberian meeting on Rheology (IBEREO), celebrado del 4 al 6 de septiembre de 2019 en Oporto (Portugal), Chitosan (Ch) is a biodegradable cationic polymer, with industrial interest. The purpose of this study was to analyse the effect of Ch concentration (1–3%), on the rheological properties of acetic (A1–A3) and lactic (L1–L3) acid solutions. Flow curves (up-down) at 20 °C, provided the consistency (κ) and the flow index (n). In all solutions, κ increased and n decreased with Ch concentration. For L3, greater κ value and lower n exponent indicate stronger shear thinning response. The structural-breaking rate (vup), and the regeneration rate (vdown) were proposed as a measurement of the time dimension in the shear thinning response., This work has been financed by the Spanish MINECO under Project AGL2017-84161 co-funded with EU-Regional Development Fund.

A β-Lactoglobulin fraction (r-βLg) was isolated from whey hydrolysates produced with cardosins from Cynara cardunculus. The impact of the hydrolysis process on the r-βLg structure and the rheological properties of heat-induced gels obtained thereafter were studied at different pH values. Differences were observed between r-βLg and commercial β-Lg used as control. Higher values for the fluorescence emission intensity and red shifts of the emission wavelength of r-βLg suggested changes in its tertiary structure and more solvent-exposed tryptophan residues. Circular dichroism spectra also supported these evidences indicating that hydrolysis yielded an intermediate (non-native) β-Lg state. The thermal history of r-βLg through the new adopted conformation improved the microstructure of the gels at acidic pH. So, a new microstructure with better rheological characteristics (higher conformational flexibility and lower rigidity) and greater water holding ability was founded for r-βLg gel. These results were reflected in the microstructural analysis by scanning electron microscopy. Fil: Estévez, Natalia. Universidad de Vigo; España Fil: Fuciños, Pablo. International Iberian Nanotechnology Laboratory; Portugal Fil: Bargiela, Verónica. Universidad de Vigo; España Fil: Picó, Guillermo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; Argentina Fil: Woitovich Valetti, Nadia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; Argentina Fil: Tovar, Clara Asunción. Universidad de Vigo; España Fil: Rúa, M. Luisa. Universidad de Vigo; España

This paper examines the physicochemical and rheological properties to determine the freezing and frozen stability of restructured fish prototypes made with glucomannan (GM) and fish mince lacking any protein functionality. The effect of adding salt and fish oil to the fish prototype formulae is also examined. Three prototype fish gels at 1.25% final GM concentration were made: control lot (C); oil lot (O): control gels with 5% added fish oil, and salt lot (S): control gels were made with 0.8% NaCl. The analyses were performed after 24h refrigerated storage (5°C) and 30, 90 and 150 days frozen storage at -20°C.Freezing produced hardening of gels due to partial dehydration caused by ice crystal formation, particularly in Lot S where the gels were more rigid with less water binding capacity (WBC) and more cooking loss (CL) after 30 days storage. Conversely, lot C exhibited some synergy between GM and protein molecules, giving time-stable networks with higher WBC after freezing. Lot O showed less CL and a more regular trend in mechanical and viscoelastic parameters between 90 and 150 days frozen storage, demonstrating the stabilizing effect of the >oil-protein-water> complex in a GM matrix. © 2014 Elsevier Ltd.

This paper focuses on the relationship between network structure and physicochemical and rheological properties of aqueous glucomannan dispersions (AGD) as a function of pH, to establish optimal conditions of glucomannan gelation for making restructured seafood products. Various lots of AGD were prepared from 3% (L1) and 5% (L2) konjac glucomannan adding different amounts (0.5–5%) of 0.6 N KOH to obtain samples with successively increasing degrees of alkalinity, from pH = 8.9 to = 11.9 (samples L1.1–L1.6 for 3% AGD) and from pH = 7 to 11.4 (samples L2.1–L2.6 for 5% AGD). The spectra of the different AGDs were obtained by Fourier Transform Infrared spectroscopy (FT-IR) to quantify the deacetylation ratio, whose effect on the physicochemical, mechanical (puncture), viscoelastic (at both small and large time scales) and structural characteristics (scanning electron microscopy (SEM)) was analysed. A linear dependence was found between the relative area of acetyl bands of AGD and pH, showing a discontinuous region in the function or gap zone between pHs 9.3 (L1.2) and 9.8 (L1.3) for 3% AGD and between 9.2 (L2.3) and 10.7 (L2.4) for 5% AGD. Samples before the gap zone (L1.2 and L2.3) were gels of varying degrees of weakness, becoming strong gels thereafter. The gelation conditions were best at pH ∼ 10.7 for both 3 and 5% AGDs, corresponding to high and moderate deacetylation ratio, respectively. The resulting gels possessed elastic, cohesive and time-stable networks and thus formed basic structures able to contain several ingredients for making restructured seafood products. The SEM photographs corroborated the physicochemical and rheological characteristics.

© 2014, Springer Science+Business Media New York. High hydrostatic pressure (HHP) processing was used to determine its ability to induce protein gelation. Isolated hake myofibrils were processed by HHP at 0, 150, 250, and 500 MPa (10 ºC/10 min) and/or by heating (90 ºC/20 min). The results were analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), determination of sulfhydryl group contents, and dynamic rheometry measurements. FTIR data indicated that secondary protein structures exhibited a reduction in α-helix together with an increase in β-sheet as a result of protein denaturation caused by HHP. DSC showed that HHP induced a reduction in myosin denaturation temperature (Tpeak) indicating protein unfolding. Protein gelation after HHP is based on physical (non-covalent) interactions which make more sulfhydryl groups available, while after heating, it is based on the formation of covalent (disulfide) bonds as a consequence of protein denaturation reducing the sulfhydryl groups. The combination of HHP and heating, particularly the latter, improved network stabilization. These results were reflected in the rheological changes, in which heated gels showed more elastic, cohesive, and time-stable networks than pressurized (non-heated) gels. The HHP effect provided softer, more flexible networks. The gel at 500 MPa was the most elastic and time-stable and exhibited the highest level of connectivity., s The authors would like to thank the Spanish Ministry of Economy and Competitiveness and the Spanish National Research Council (CSIC) for supporting the project AGL2011-24693. The authors also wish to thank the Xunta de Galicia for its financial support under the consolidation and restructuring program of competitive research units: Strategic Research Partnerships (2009/060).

Structural (cryo-scanning electron microscopy), and viscoelastic changes (dynamic rheometry), with storage time in Afuega'l Pitu cheese Blancu (B) and Roxu (R) varieties were observed. Biochemical parameters were also measured. pH, fat, and protein content did not change during the storage time for B and R varieties. R micrographs showed large fused-fat particles within the protein matrix, as a consequence of a specific kneading step to mix the partially dehydrated curd with paprika and salt. B samples exhibited more homogeneous microstructures with small fat globules, improving viscoelastic parameters such as conformational stability (stress amplitude, σmax) and network flexibility (strain amplitude, γmax). The longer storage time, the higher total solids (TS) content (lower moisture to protein ratio-MPR) for B and R varieties, evolving into a less porous microstructure, which increased the thickening of the protein strands. These structural changes were shown in the enhanced rigidity (high complex modulus, G*), structural stability (high σmax) and more shear-sensitive or physically structured (lower γmax) cheese network.

Native glucomannan (Lot A; pH = 5.3) and weakly deacetylated glucomannan (Lot L; pH = 9.1) gels were subjected to high hydrostatic pressure (HHP): 100, 200, 400, and 600 MPa and studied the influence of HHP on the structural and rheological properties of glucomannan gels. HHP improved the conformational stability, reticular deformability and the energy stability of hydrogen bonds in junction zones of the glucomannan matrix for lot A gels. For lot L gels, 600 MPa was needed to increase the energy content of physical bonds enhancing the solid-like character of the glucomannan matrix. Thermal profiles of pressurized lot A gels exhibited thermophobic behaviour and increased the gel-like character up to 90°C as compared with its unpressurized control. For Lot L gels, the rubber-like response was also shown at T > 70°C for the unpressurized sample, and was maintained at 100, 200, and 600 MPa., This work was supported by the Consejo Superior de Investigaciones Científicas for Postdoctoral Scholarship JAEDOC-2011 [grant number AGL2011-24693]. The authors wish to thank the Xunta de Galicia for its financial support under the Consolidation and restructuring program of competitive research units: Strategic Research Partnerships [grant number 2009/060].

Four dispersions of 3% glucomannan in water, deacetylated with 5% 0.6N and 1N KOH (lots L1 and L2) and 0.6N and 1N NaOH (lots L3 and L4) as gelling agents, were evaluated for use in raw restructured seafood products. Several properties (pH, moisture content, water binding capacity, cooking loss and lightness) together with puncture data (breaking force and breaking deformation) were determined after 1 and 10 days of chilled storage at 5°C. All these data were analyzed together with different viscoelastic parameters obtained at small amplitude oscillatory strain (SAOS) after 1 day of chilled storage, showing that L1 and L4 samples were the most suitable gels for incorporation in raw restructured fish products. In both cases the highest stress (σmax) and strain (γmax) amplitude values were found in the linear viscoelastic (LVE) range; however, L1 showed both high strain amplitude and breaking deformation values. Moreover, creep and recovery (transient) data showed that L1 was the most time-stable gel with the highest elasticity and the lowest relaxation exponent (n). L4 gel showed strong rigidity, i.e. the highest values of breaking force and storage moduli (G') and the highest n value, making it less gel-like. Both L1 and L4 gels became significantly less gel-like over 10 days of chilled storage due to the loss of gel strength (S) and a noticeable increase of n. These chilled storage effects were more intense in L4 than in L1. © 2011 Elsevier Ltd.

The influence of the amount of egg albumen contained as a gelation agent in crab sticks made from Alaska Pollock or Pacific Whiting surimi on their viscoelastic properties was examined. Dynamic oscillatory and transient tests allowed a variety of parameters to be measured in order to establish the intensity of the interactions in the protein network which characterize the gel strength. This physical property is fundamental for the nominal quality texture and eating quality of surimi and surimi-based seafood analog products (surimi seafood). Three different egg albumen contents around the nominal value (2%) were studied, namely: 1.5, 2 and 2.5%. The viscoelastic gel strength (An) and gel strength (S) values obtained in the frequency sweep and creep tests, respectively, were quite consistent. Increasing the protein content of the surimi increased the gel strength of both types of crab sticks (p

Two new methods were designed for making surimi from giant squid (Dosidicus gigas) muscle. The first is based on protein precipitation at the isoelectric point (type A), and the second on washing with an acid solution (type B). Chemical analyses (e.g. protein solubility, electrophoretic profile), structural analyses (scanning electronic microscopy) and above all rheological analyses were carried out. Small amplitude oscillatory tests were performed to evaluate the influence of these two methods on the viscoelasticity and gel-forming ability of squid surimi. The results showed that method B preserves the functionality of the myofibrillar proteins better, thus making for a better gel structure than method A. Moreover, the addition of different cryoprotectants (sorbitol + sucrose, sorbitol + trehalose, trehalose alone), resulted in essential differences between the two kinds of surimi. In surimi A, trehalose favoured less initial protein aggregation and hence a thermorheologically stable structure, with a better gelation profile than sorbitol + sucrose or sorbitol + trehalose, in surimi, suwari-gels and definitive-gels alike. However, in B samples the influence of different cryoprotectants was not discernible. © 2009 Elsevier Ltd. All rights reserved., This work has been supported by the Spanish Ministerio de Ciencia e Innovación under Project AGL2005-04347

Changes in viscoelastic properties as a function of the wheat starch content of crab sticks from Alaska Pollock and Pacific Whiting surimi determined from transient and oscillatory measurements were studied. Based on the frequency dependence of the complex shear modulus (G∗), the two types of sticks were discriminated in terms of gel stiffness (An) and the difference (G0′ − G0″) as a function of starch content. Creep and recovery tests allowed gel strength, S, to be determined from the relation modulus, G(t). This body of parameters provides an interesting method for the industrial assessment of the nominal quality of surimi and its derivatives. Overall, the tests revealed that stiffness and hardness in the product increase with increasing starch contents. Specifically, the optimum starch content for Alaska Pollock sticks was found to be 11%, above which the product becomes unacceptably hard and brittle. By contrast, the optimum starch content for Pacific Whiting sticks was 11–15%, which reflects a decreased gelling capacity of this type of surimi.

A β-Lactoglobulin fraction (r-βLg) was isolated from milk whey hydrolysates produced with cardosins from Cynara cardunculus. The impact of the technological process on the r-βLg structure and how in turn this determined its heat-induced gelation was investigated. Results were analysed taking pure β-Lg (p-βLg) as control sample. The process induced changes in the r-βLg native conformation causing exposure of hydrophobic groups, lower thermal stability and also, shorter thermal treatments needed to give rise to non-native and aggregated species. At pH 3.2, r-βLg and p-βLg solutions exhibited two gelation steps, with the advantage that r-βLg protein may form stable gels at lower temperature than p-βLg. At pH 7.2, a specific thermo-viscoelastic stability to 73 °C was found, which corresponded to the gel point in both protein solutions. The difference was that while for p-βLg solution in sol state δ45° (solid-like), however for r-βLg solution δ45° (fluid-like).

Isobaric molar heat capacities, densities and speeds of sound were determined for the dimethyl carbonate + n -octane and n -nonane systems at atmospheric pressure covering the whole composition interval and in the temperature range (288.15–308.15 K). From these data, derived properties and excess magnitudes were obtained. A strongly temperature-dependent W-shaped curves against composition were observed for excess isobaric molar heat capacities in both system, showing the other excess magnitudes regular tendencies. From these results, a comparative analysis of the existing differences between the thermodynamic behaviour of the two systems was carried out.

Carboxymethylcellulose (CMC) samples with different degrees of substitution were obtained from Eucalyptus globulus pulps made in formic acid-peroxyformic acid medium (Milox delignification) and subjected to Totally Chlorine Free bleaching. In order to assess the rheological behaviour of the synthesized materials, their properties (rheological behaviour, solubility and molar mass) were determined and examined in relation to their total degree of substitution. Additional discussion on the structure and purity of pulps, alkali celluloses, and CMC is provided.

Controlled shear stress tests were used to monitor the changes of viscoelastic properties in industrial samples of Tetilla cheese with the ripening time. The linear viscoelastic range was determined from both stress sweep and creep-and-recovery tests conducted at 20ºC. One-week-old samples were found to be more rigid and elastic, and to exhibit broader linear ranges, than older samples. Mechanical spectra recorded at the same temperature confirmed this trend since viscoelastic moduli G’ and G" decreased markedly during the first week of ripening, indicating a loss of structure during this period. Besides, physico-chemical information (pH, water content, protein content, nitrogen fractions, and s1 and β casein fractions) was obtained by analytical methods. Quite good correlation between rheological and chemical results was found. For each ripening time, an additional study of mechanical spectra as a function of temperature was performed. A marked increase of the power law exponents as temperature is raised is observed after the second week. Crosslink breakdown and the resulting structural weakening of the micellar network through casein hydrolysis during ripening can explain this result. The whole study provided similar results to those found for other type of cheeses and, also, allowed the classification of samples into two groups of markedly different behaviour, namely, one-week-old samples and older samples. In conclusion more than one week of ripening is needed to reach the adequate texture standardisation of Tetilla cheese.

Changes in viscoelastic properties during the ripening of three different batches of Arzua-Ulloa cheese, a traditional Spanish variety, were studied. Proteolysis changes were determined in terms of the typical nitrogen fractions, these fractions were significantly correlated with the measured viscoelastic properties. Substantial changes in stress amplitude over the linear viscoelastic range were observed at 20C, as were significant differences in storage modulus (G′) and viscous modulus (G″) throughout the ripening period. Both moduli decreased markedly over the first two weeks, but exhibited an opposite trend from the third week. Mechanical spectra were recorded at 20, 25, 30 and 35C throughout the ripening period. The viscous component significantly increased compared to the elastic one as function of temperature and ripening time.

© 2015 Elsevier Ltd. This study examines the effect of high pressure processing on frozen low-grade surimi to improve its gelation properties. Flying fish surimi (FFS) was subjected to low-intensity pressures (0, 40, 80 and 200MPa/-15°C/10min) to reduce the processing cost. Physicochemical and rheological properties of gels (suwari gels -S-: 5°C/24h and definitive gels -G-: 40°C/30min+90°C/30min) made with this pressurized surimi were determined. Results indicated that regardless of the level of hydrostatic high pressure (HHP) processing, suwari gels exhibited more native protein structure (more α-helix and less β-structures) than control sample (without HHP) or the initial raw material. Breaking force (BF) and breaking deformation (BD) increased in suwari and definitive gels with the increase in pressure as compared with their control (non-pressurized) suwari gels (0S) and definitive gels (0G). Viscoelastic parameters confirmed that after HHP (except 80MPa) processing, suwari gels made from frozen surimi were more elastic and energy-stable, especially at 200MPa. The beneficial effect of HHP processing on mechanical properties was independent of the pressure applied in the heat-induced definitive gels; however, there was no improvement in viscoelasticity., The authors would like to thank the Spanish Ministry of Economy and Competitiveness and the Spanish National Research Council (CSIC) for supporting the project AGL2011-24693.

An experimental study of the behaviour of the second-order excess derivatives against composition and temperature for the 1,3-dichloropropane + n-dodecane system is presented. To this end, densities and speeds of sound were obtained in the interval 278.15-328.15 K with a step of 1 K. In addition, isobaric molar heat capacities were obtained in the temperature range 283.15-323.15 K. Measurements were performed over the whole composition range and at atmospheric pressure. Isentropic compressibilities were determined using the Laplace equation, and isobaric thermal expansivities were obtained in the interval 283.15-323.15 K from density data. Isothermal compressibilities and isochoric molar heat capacities within 283.15-323.15 K were derived from the above-mentioned properties via appropriate thermodynamic relations. The excess quantities for these properties were calculated using the ideality criterion first proposed by Benson and Kiyohara. Destruction of the 1,3-dichloropropane dipolar order during mixing appears to be the main effect to which the excess properties are sensitive.

Isobaric molar heat capacities at 288.15, 298.15, and 308.15 K and densities and speeds of sound at 288.15, 293.15, 298.15, and 308.15 K were determined for the dimethyl carbonate + benzene system over the whole composition range and at atmospheric pressure. In addition, speeds of sound at the same temperatures for the dimethyl carbonate + n-heptane system are reported. These experimental data were used to obtain molar volumes, isobaric thermal expansivities, isentropic and isothermal compressibilities, and isochoric molar heat capacities. Excess quantities of the above-mentioned properties were calculated using the Benson and Kiyohara criterion. The thermodynamic behaviour of the dimethyl carbonate + (n-heptane, cyclohexane, benzene, or toluene) systems is comparatively analyzed.Key words: binary mixtures, excess properties, dimethyl carbonate, benzene, hydrocarbon.

A simple association model for alcohol−alkane mixtures, based on the idea that only two energy states are accessible to alcohol molecules in the pure and in the solution states, predicts complex temperature and alcohol concentration dependences of the excess molar heat capacity, . These predictions are tested through the accurate measurement of pure component and solution heat capacities in the 278.15−338.15 K temperature interval. These measurements were performed at low, equimolar, and high alcohol concentrations for a linear alcohol (1-butanol) and a branched alcohol (3-methyl-3-pentanol) mixed with n-decane and with toluene. The qualitative predictions from the two-state model are corroborated by the data. According to this model, the very different behaviors found for the different systems arise simply through the change in hydrogen bonding Gibbs energy occurring on moving from the linear to the branched alcohol and in going from the inert n-decane to the aromatic toluene.

A methodology for the thermophysical characterization of liquids and liquid mixtures based on measurements of density, sound speed and isobaric heat capacity per unit volume at atmospheric pressure as a function of temperature is proposed. Density and sound speed data are used to determine the isentropic compressibility from the Laplace equation. The precision in density measurements allows one to obtain the isobaric thermal expansivity at different temperatures using an incremental procedure with quite acceptable accuracy and precision. The isothermal compressibility and isochoric molar heat capacity are both obtained from the previous properties, using well-known thermodynamic relations. The accuracy of the proposed methodology was checked by determining the above-mentioned properties for liquid n-hexane, n-heptane, n-octane, n-dodecane, n-hexadecane, cyclohexane, and toluene over the temperature range (288.15–333.15) K and comparing the results with selected reported data. The average absolute deviations from the latter showed data obtained with the proposed methodology to be reasonably accurate. The excess quantities for nine binary mixtures of the cyclohexane + n-dodecane system were also determined with a view to assessing precision, which was found to be quite good as regards the dependence on both composition and temperature.