Rheological and Microstructure Characterization of Composite Dough with Wheat and Mesquite (Prosopis spp) Flours

Rheological behavior and microstructural characteristics of composite dough with wheat and mesquite flours (from Prosopis alba) were analyzed by response surface methodology. A central composite design was applied varying proportions of water (50 to 80 g each 100 g wheat flour) and mesquite flour (0 to 70 each 100 g wheat flour). Texture profile analysis showed that increasing the amount of mesquite flour and decreasing the amount of water led to less cohesive and more resilient doughs. Stress relaxation curves were fitted with a Maxwell model and relaxation times were obtained. These parameters resulted higher for those formulations low in mesquite content and high water levels. Composite dough showed a typical viscoelastic behavior with higher elastic moduli (G) when mesquite flour ratio in the mixture was increased. 1H-RMN T2 relaxation assays revealed higher mobility in samples with high amounts of water and minimum level of mesquite. A farinograph was adequate to obtain optimum water amounts and showed that addition of mesquite led to less stable dough respect to control wheat dough. By using confocal laser scanning microscopy with fluorescent probes rhodamine B and fluoresceine isothiocyanate, a poor gluten network development or protein aggregation was observed when water contents were far from optimum.Fil: Bigne, Facundo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Puppo, Maria Cecilia. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Ferrero, Cristina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin

Magnetic Field Effects on Molecular Emissivity in Solutions

Control over dynamics of excited states of molecules is fundamental to utilization of these states in all areas of technologies, including optical microscopy and tomography. We explored the possibility of magnetically controlling molecular emissivity by influencing spin dynamics in radical pairs (RPs) and triplet-triplet pair. We envisioned that by including RPs into a pathway leading to the formation (or decay) of an emissive triplet state, magnetic influence on phosphorescence could be realized via modulation of the RP\u27s spin dynamics. RPs can initially be produced in their singlet or triplet spin state. These two cases were explored in the studies of electron and energy dynamics in series of donor-acceptor systems, comprising phosphorescent platinum (II) porphyrins (PtP) and rhodamine B (RhB+) derivatives. In one series, the phosphorescent triplet state of PtP is generated by way of photo-excitation of RhB+, followed by photoinduced electron transfer with formation of a singlet-born RP, RP intersystem crossing, and subsequent recombination of the triplet RP. Similarly, singlet-born RPs were included into a pathway leading to PtP triplet state in a triad system comprising PtP, anthracene, and boron dipyrromethene. Using another series, we have demonstrated that visible room-temperature phosphorescence can be modulated by weak magnetic fields (\u3c1T). In this case, the RP is initially born in its triplet state upon direct excitation of PtP, followed by electron transfer originating in the PtP triplet state. External magnetic field modulates spin dynamics in the RP, affecting contribution of the singlet charge recombination channel and thereby influencing the phosphorescence. Spin dynamics of triplet-triplet pair is also susceptible to magnetic field. Triplet-triplet pair can undergo triplet-triplet annihilation (TTA) process leading to photon upconversion, which is typically observed as p-type delayed fluorescence. We have demonstrated TTA-sensitized delayed fluorescence and delayed phosphorescence, mediated by near-infrared absorbing metalloporhyrins as sensitizers in solution at room temperature, can be magnetically modulated. These studies present unusual and interesting examples of magnetic field effects on molecular emission and set the stage for rational design of optical imaging probes with magnetically controlled emissivity

Comparación entre harinas de dos especies de algarrobo (<i>Prosopis</i> sp.) del norte argentino

Se conoce como algarrobo a un grupo de 44 especies de plantas alrededor del mundo de las cuales 24 son endémicas del territorio argentino. El algarrobo blanco (Prosopis alba) y el algarrobo negro (Prosopis nigra) son dos de las especies de mayor importancia para los habitantes del Noroeste argentino. El conocimiento de la composición química y nutricional del fruto del algarrobo y de las harinas derivadas del mismo contribuye al agregado de valor de los diferentes productos alimenticios elaborados con harina de algarrobo. Para obtener las harinas se secaron las vainas en estufa de convección durante 4hs a 80°C, luego se utilizó un molino domestico para molerlas y se las paso a través de un tamiz de 1000 μm; a las fracciones se les determinó: humedad (AOAC 925.45), proteínas utilizando como factor 6,25 (AOAC 920.142), lípidos (AOAC 963.15), fibra total (AOAC 991.43), ceniza (AOAC 923.03), minerales por espectrofotometría de absorción atómica (Na, K, Ca, Fe, Mg, Mn, Zn), azúcares mediante HPLC con columna amino y detector de índice de refracción, polifenoles utilizando la técnica de Folin Ciocalteu (g ácido gálico/100g de harina b.s.) y capacidad antioxidante por método ABTS (moles Trolox equivalente/100g de de harina b.s.). Se utilizaron duplicados de muestra y todos los resultados se expresaron en base seca. Los resultados se analizaron mediante análisis de la varianza y los valores medios se compararon con el test de Fisher (p<0,05). Los resultados obtenidos demostraron que no se encontraron diferencias significativas entre harinas en el porcentaje de proteínas de un 7,8%; ceniza 3,2%; Na 700 ppm; Zn 18 ppm; sacarosa 53%; fructosa 2,5%, siendo estos valores promedios de las dos harinas. Sin embargo se encontraron diferencias significativas entre P. alba y P. nigra para lípidos 0,68% y 6,59%; fibra total 20% y 23%; K 9030 y 10600 ppm; Ca 1860 ppm y 1610 ppm; Mg 560 ppm y 690 ppm; Fe 49 ppm y 26 ppm, Mn 4,7 ppm y 7,7 ppm; polifenoles 0,621% y 1,081%, respectivamente. La capacidad antioxidante también resultó significativamente diferente: 5450 y 9350 μmol/100g para P. alba y P. nigra, respectivamente. Se puede concluir en base a los resultados que las composiciones de las harinas son diferentes estadísticamente aunque guardan una relación en cuanto a la composición. Sin embargo, no se puede concluir fehacientemente que una harina destaca sobre la otra, ambas harinas se obtienen a partir de vainas que actualmente se encuentran sub-utilizadas, son fáciles de obtener, permitiendo contar con un nuevo ingrediente para alimentos, especialmente productos horneados.Centro de Investigación y Desarrollo en Criotecnología de AlimentosLaboratorio de Investigación en Productos Agroindustriale

Effect of different hydrocolloids on thermal transitions and molecular mobility in wheat flour dough

En el presente trabajo se analizó la influencia de hidrocoloides sobre la gelatinización de almidón, y la cantidad de agua congelable a través de calorimetría diferencial de barrido. Se estudió también la movilidad molecular del sistema a través de ensayos de tiempo de relajación, λ, por resonancia magnética nuclear (1H spin-spin RMN). Se utilizaron como sistemas modelo masas frescas y liofilizadas, preparadas a partir de harina de trigo comercial (tipo 000, CAA) con distintos hidrocoloides (1,5 g/100g harina): goma guar (GG), goma xántica (GX), goma garrofín (LBG), pectina de alto metoxilo (P) y la mezcla de garrofin y xántica 50:50 (LBG+GX) cuyos valores de absorción farinográfica (A) fueron 62,1%, 66,4%, 66%, 62%, 65,5%, respectivamente. Se evaluó la gelatinización del almidón obteniéndose temperatura inicial (Ti), de pico (Tp), final (Tf) y la entalpía del proceso. En las masas frescas elaboradas con agua farinográfica se observó una disminución de la Tf respecto al control con el agregado de LBG+GX, LBG y GX. Las masas liofilizadas y rehidratadas en relación sólido:agua 1:0,5, presentaron un corrimiento de ambos picos del termograma, cuyas Tp (TpI y TpII) se vieron incrementadas por el agregado de hidrocoloides en la mayoría de los casos. La Tf aumentó significativamente con LBG+GX, LBG, GX y GG. Las variaciones en las temperaturas observadas se pueden relacionar con la disminución de cantidad de agua disponible para la gelatinización cuando la muestra contiene hidrocoloide. El porcentaje de agua congelable de las masas frescas aumentó significativamente respecto al control cuando se agregó la mezcla LBG+GX. De los datos obtenidos por RMN se observó que en las masas la movilidad molecular aumentó en forma creciente respecto a la masa control con el agregado de LBG, GX y LBG+GX, no varió con el agregado de GG y disminuyó significativamente con P. Estos resultados sugieren que los hidrocoloides interactúan con los componentes de la masa en forma diferente según su estructura, generando en particular un cambio en la disponibilidad de agua para procesos como la gelatinización del almidón y la congelación y una alteración en la movilidad de los protones del sistema, probablemente relacionada con una reestructuración de la matriz. El estudio más detallado de estos cambios es relevante en la masa panaria dado el rol de las interacciones del agua con proteínas de gluten y almidón.In the present work, the influence of hydrocolloids on starch gelatinization and freezable water was evaluated by differential scanning calorimetry- The molecular mobility of the system was also studied by RMN relaxation assays (1H spin-spin RMN). Guar gum (GG), xanthan gum (XG), locust beam gum (LBG), high methoxyl pectin (P) and the mixture of locust beam gum and xanthan gum 50:50 (LBG+XG) were employed at a 1.5 g/100g flour level. Farinographic water absorption (A) values of blends were 62.1 %, 66.4 %, 66.0 %, 62.0 %, 65.5 %, respectively. A commercial wheat flour was used. The following starch gelatinization parameters were obtained: onset temperature (Ti), peak temperature (Tp), final temperature (Tf) and gelatinization enthalpy. In fresh doughs, obtained with the farinographic amount of water, a decrease in Tf, respect to control, was observed when LBG+GX, LBG and GX. were added. Lyophilized and rehydrated doughs (solids:water = 1:0.5) exhibited a shift of both peaks in thermograms, with the Tp (TpI y TpII) values increased in most cases because of hydrocolloid addition. Tf significantly increased by addition of LBG+GX, LBG, GX and GG. The variations in temperature can be related to the decrease in the quantity of water available for the gelatinization process when the sample contains hydrocolloids. The percentage of freezable water of fresh dough significantly increased respect to control with the addition of the mixture LBG+XG. By NMR assays, it could be observed that the molecular mobility increased with the addition of LBG, XG and LBG+XG. No differences in relaxation time were observed when GG was added but a significant decrease was observed when P was incorporated. From these results, it can be concluded that hydrocolloids can interact with the other dough components in different ways according to their structure, thus inducing a change in water availability for processes like starch gelatinization and freezing. A change in protons mobility was observed, probably related to restructuring of the system matrix. A more detailed study of these changes is relevant in bread dough taking into account the role of the interactions among water, gluten proteins and starch.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Addition of value to <i>Prosopis alba</i> fruit: study of chemical and nutritional properties for its application in sweet healthy snack formulations

El objetivo de este trabajo fue estudiar la calidad química y nutricional de harinas de vaina y pulpa del fruto de algarrobo y su aplicación como agente aglutinante en la formulación de bocaditos dulces a base de semillas andinas (quinua, amaranto y chía). Se realizó un diseño de mezclas manteniendo constante la proporción de semillas y en el que se variaron los tres ingredientes considerados como aglutinantes y endulzantes: harina de algarroba, azúcar y miel. El diseño fue sometido a una restricción, que consistió en que no se formuló un bocadito con harina de algarroba sólo como aglutinante. Se evaluó en los bocaditos la masticabilidad por ensayos de perfil de textura y la aceptabilidad sensorial con un panel no entrenado que realizó un ordenamiento por preferencia con niveles de 1 a 5 (1: la que más me gusta a 5: la que me gusta menos) para las cinco muestras del diseño. La harina de vaina presentó bajo contenido de lípidos y proteína libre de prolaminas; pero alto contenido de azúcares solubles, principalmente sacarosa y de fibra dietaria insoluble. Esta harina presentó un alto contenido de calcio, potasio, magnesio y cinc, como también un nivel importante de polifenoles, tanto en pulpa como en semilla, que contribuyen a la capacidad antioxidante. Esta harina con propiedades nutricionales por su contenido de fibra, minerales y antioxidantes fenólicos, resultó apta para alimentos dulces destinados a personas celíacas. Asimismo, los bocaditos dulces elaborados con la harina de vaina resultaron sensorialmente aceptados por los consumidores.The objective of this work was to study chemical and nutritional aspects of Prosopis alba pods and pulp, and the application of these flours as agglutinant agents in sweet snacks formulated with Andean seeds (quinoa, amaranth, chia). Snacks were formulated with constant proportion of seeds and variable amounts of agglutinants (sugar, honey and carob flour) according to an experimental design for constrained mixtures. Texture profile analysis (chewiness) and sensory analysis by a non-trained panel (preferences test) were conducted on the snacks. In the preference test, with a scale from 1 to 5, the value 1 was assigned to the less liked sample, while the value 5 corresponded to the most liked one. Prosopis alba pod flour was prolamin-free, presented low lipid content and was rich in soluble sugars (mainly sucrose) and insoluble dietary fiber. This flour presented high level of calcium, potassium, magnesium and zinc; and was rich in phenolic antioxidants. This flour with good nutritional properties due to fiber, mineral and phenolic antioxidants is suitable for sweet foods destined to celiac people. In addition, sweet snacks elaborated with Prosopis alba pod flour were well accepted by consumers.Facultad de Ciencias Agrarias y Forestale

Addition of value to <i>Prosopis alba</i> fruit: study of chemical and nutritional properties for its application in sweet healthy snack formulations

El objetivo de este trabajo fue estudiar la calidad química y nutricional de harinas de vaina y pulpa del fruto de algarrobo y su aplicación como agente aglutinante en la formulación de bocaditos dulces a base de semillas andinas (quinua, amaranto y chía). Se realizó un diseño de mezclas manteniendo constante la proporción de semillas y en el que se variaron los tres ingredientes considerados como aglutinantes y endulzantes: harina de algarroba, azúcar y miel. El diseño fue sometido a una restricción, que consistió en que no se formuló un bocadito con harina de algarroba sólo como aglutinante. Se evaluó en los bocaditos la masticabilidad por ensayos de perfil de textura y la aceptabilidad sensorial con un panel no entrenado que realizó un ordenamiento por preferencia con niveles de 1 a 5 (1: la que más me gusta a 5: la que me gusta menos) para las cinco muestras del diseño. La harina de vaina presentó bajo contenido de lípidos y proteína libre de prolaminas; pero alto contenido de azúcares solubles, principalmente sacarosa y de fibra dietaria insoluble. Esta harina presentó un alto contenido de calcio, potasio, magnesio y cinc, como también un nivel importante de polifenoles, tanto en pulpa como en semilla, que contribuyen a la capacidad antioxidante. Esta harina con propiedades nutricionales por su contenido de fibra, minerales y antioxidantes fenólicos, resultó apta para alimentos dulces destinados a personas celíacas. Asimismo, los bocaditos dulces elaborados con la harina de vaina resultaron sensorialmente aceptados por los consumidores.The objective of this work was to study chemical and nutritional aspects of Prosopis alba pods and pulp, and the application of these flours as agglutinant agents in sweet snacks formulated with Andean seeds (quinoa, amaranth, chia). Snacks were formulated with constant proportion of seeds and variable amounts of agglutinants (sugar, honey and carob flour) according to an experimental design for constrained mixtures. Texture profile analysis (chewiness) and sensory analysis by a non-trained panel (preferences test) were conducted on the snacks. In the preference test, with a scale from 1 to 5, the value 1 was assigned to the less liked sample, while the value 5 corresponded to the most liked one. Prosopis alba pod flour was prolamin-free, presented low lipid content and was rich in soluble sugars (mainly sucrose) and insoluble dietary fiber. This flour presented high level of calcium, potassium, magnesium and zinc; and was rich in phenolic antioxidants. This flour with good nutritional properties due to fiber, mineral and phenolic antioxidants is suitable for sweet foods destined to celiac people. In addition, sweet snacks elaborated with Prosopis alba pod flour were well accepted by consumers.Facultad de Ciencias Agrarias y Forestale

1D selective confinement and diffusion of metal atoms on graphene

The role of moiré graphene superstructures in favoring confined adsorption of different metal atoms is an intriguing problem not yet completely solved. Graphene (G) grown on Ni(100) forms a striped moiré pattern of valleys, where G approaches the nickel substrate and interacts with it rather strongly, and ridges, where G stays far away from the substrate and acts almost free-standing. Combining density functional theory (DFT) calculations and scanning-tunneling microscopy (STM) measurements, we show that this peculiar moiré constitutes a regular nanostructured template on a 2D support, confining in 1D trails single metal atoms and few atoms clusters. DFT calculations show that the confinement is selective and highly dependent on the atomic species, with some species preferring to adsorb on ridges and the other showing preference for valleys. Co and Au adsorbates, for instance, have opposite behavior, as predicted by DFT and observed by STM. The origin of such disparate behavior is traced back to the electrostatic interaction between the charged adsorbate and the nickel surface. Moreover, the selectivity is not restricted to the adsorption process only, but persists as adsorbate starts its diffusion, resulting in unidirectional mass transport on a continuous 2D support. These findings hold great promise for exploiting tailored nanostructured templates in a wide range of potential applications involving mass transport along element-specific routes

Exceptionally Stable Cobalt Nanoclusters on Functionalized Graphene

To improve reactivity and achieve a higher material efficiency, catalysts are often used in the form of clusters with nanometer dimensions, down to single atoms. Since the corresponding properties are highly structure-dependent, a suitable support is thus required to ensure cluster stability during operating conditions. Herein, an efficient method to stabilize cobalt nanoclusters on graphene grown on nickel substrates, exploiting the anchoring effect of nickel atoms incorporated in the carbon network is presented. The anchored nanoclusters are studied by in situ variable temperature scanning tunneling microscopy at different temperatures and upon gas exposure. Cluster stability upon annealing up to 200 °C and upon CO exposure at least up to 1 × 10−6 mbar CO partial pressure is demonstrated. Moreover, the dimensions of the cobalt nanoclusters remain surprisingly small (<3 nm diameter) with a narrow size distribution. Density functional theory calculations demonstrate that the interplay between the low diffusion barrier on graphene on nickel and the strong anchoring effect of the nickel atoms leads to the increased stability and size selectivity of these clusters. This anchoring technique is expected to be applicable also to other cases, with clear advantages for transition metals that are usually difficult to stabilize

Rheological properties of emulsions containing modified soy protein isolates

The feasibility of replacing common emulsifiers with soy protein isolates (SPI) in low-calorie salad dressings was evaluated. Structural modifications of SPI were obtained by thermal-acidic treatment with or without neutralization (TH1.6N and TH1.6, respectively). Modification of flow properties of TH1.6 and TH1.6N emulsions by thermal treatment and different protein concentrations was evaluated through shear stress vs. shear rate measurements in a rotational viscometer. TH1.6N isolates generated emulsions with higher shear stress and apparent viscosity than those prepared with TH1.6. Heated TH1.6N emulsions at 10% protein gave the highest values of shear stress and plastic flow behavior. These emulsions had high consistency, viscosity, and elasticity. TH1.6N isolates had lower emulsifying capacity than TH1.6, probably due to the higher protein aggregation produced during neutralization, which prevented protein unfolding. These isolates would be suitable for the preparation of stable emulsions with adequate consistency and elasticity.Centro de Investigación y Desarrollo en Criotecnología de Alimento