La química en contexto agropecuario: un desafío

La Química en Contexto pretende establecer principios químicos en la necesidad de los saberes básicos dentro de un contexto en el marco de temas sociales, políticos, económicos y éticos. La química en contexto permite que estudiantes de áreas no estrictamente relacionadas con las ciencias químicas, como lo pueden ser la agropecuaria y forestal, puedan adquirir los conocimientos químicos básicos y las competencias para evaluar mejor los riesgos y beneficios y adquirir destrezas para contar con mayor información a la hora de tomar decisiones ante problemáticas tecnológicas. La palabra “contexto” deriva del latín contextus, que significa entrelazar, entramar; es decir, a partir de un hecho o situación se llega al núcleo temático central. Por ejemplo, tratando en forma previa la problemática de la lluvia ácida y la contaminación ambiental, se puede llegar a conceptos básicos de química como el de ácidos, bases, neutralización, pH, reacciones químicas de corrosión, entre otros. Resulta así un desafío, para alumnos del curso de Química General e Inorgánica que recién comienzan el trayecto universitario, lograr contextualizarles los diferentes conceptos químicos a fin de que puedan establecer un nexo amigable con esta disciplina denominada Química.Eje temático 2: Los cambios e innovaciones en los procesos de formación a - Alternativas didácticas y experiencias de renovación de la enseñanzaFacultad de Ciencias Agrarias y Forestale

Rheological study of dispersions prepared with modified soybean protein isolates

Structural modifications of modified soy protein isolates (SPI) were distinguished by rheological behavior. SPI were prepared by acidic (pH 2.5) and thermal-acidic treatment without (pH 1.6) and with neutralization (pH 8.0). Dynamic properties of dispersions were determined through the variation of storage and loss moduli with frequency, and loss tangent behavior was analyzed. Changes in viscoelastic parameters with protein concentration (10–12% wt/vol) and time of heating (15–60 min) were also determined. Flow properties of dispersions were estimated through apparent viscosity and flow and consistency index measurements. Rheological behavior of dispersions was compared with those found by experiment with commercial mayonnaise, mustard, and salad dressing. The analysis of rheological parameters showed that thermally treated isolates formed dispersions with high elastic modulus and consistency index with a structure mainly stabilized by hydrophobic interactions, although no gelation process after cooling was observed. From the rheological point of view, it was deduced that thermally treated isolates could be used as ingredients in the formulation of salad dressings. The alkaline sample would be more versatile because, depending on protein concentration and thermal treatment, the consistency of its dispersions was like that in salad dressing, or similar to those of mustard and mayonnaise.Centro de Investigación y Desarrollo en Criotecnología de Alimento

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

Influence of protein concentration on the properties of crayfish protein isolated gels

Crayfish protein, present in the wastes from crayfish processing, has been investigated as an ingredient of surimi-like gel products, which may be regarded as a renewable, available, and low-cost raw material. The aim of this study was to evaluate the influence of protein concentration on the gelation behaviour and gel properties of crayfish protein isolate-based systems. Gelation was performed by heating crayfish protein isolate dispersions at 90°C for 30 min. Then, gels were cooled at 4°C and the evolution of linear viscoelastic properties upon setting was analysed for 24 h. An increase in both linear viscoelasticity and water holding capacity was found as protein concentration increased, although an asymptotic evolution was found at the highest CFPI concentrations. Scanning electron microscopy revealed occurrence of an extended cross-linked network for crayfish protein isolate gels. These results suggest that crayfish protein can be properly used as a valuable ingredient in food gels, where protein concentration may be modulated to enhance gel strength.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Pedro tiene Química en/con Agronomía : ¿Tenemos que estudiar Química en Agronomía?

Pedro tiene Química con/en Agronomía es un texto de lectura fácil y amena, que permite articular el secundario con la universidad. Su estructura tiene en cuenta las dificultades de aprendizaje mencionadas, ya que el inicio de cada capítulo contempla el aspecto de la motivación mediante una ambientación cotidiana-agronómica que tiene a Pedro como protagonista, y en la que se plantea una inquietud. Luego el desarrollo formal de un conjunto clave de conceptos es el preludio para el cierre del capítulo, en el que la inquietud se ve resuelta, y el panorama se ve ampliado a concepciones específicas del ámbito agronómico. Luego, los ejercicios y problemas de final de capítulo, en su mayoría, también están adecuados al contexto académico futuro de Pedro. El desarrollo conceptual se nutre de explicaciones fundadas en imágenes que presentan los aspectos macroscópicos, y simpáticas ilustraciones y esquemas que facilitan el proceso de abstracción de los aspectos sub-microscópicos.Facultad de Ciencias Agrarias y Forestale

High β-Glucans Oats for Healthy Wheat Breads: Physicochemical Properties of Dough and Breads

Bread is a highly consumed food whose nutritional value can be improved by adding an oat flour (Avena sativa L.-variety Bonaerense INTA Calen-Argentina) to a high-industrial quality wheat flour (Triticum aestivum L.). This cultivar of oat contains high amounts of β-glucans, which act as a prebiotic fiber. Wheat flour was complemented with different amounts of oat flour (5, 15, and 25%). A contribution of hydrophilic components from oat flour was evident in the oat–wheat mixtures. At the same time, the high content of total dietary fiber led to changes in the rheological properties of the dough. Mixtures with a higher proportion of oats showed an increase in alveographic tenacity (stiffer dough), higher stability, and a lower softening degree in farinographic assays. The dough showed significant increases in hardness and gumminess, without significant changes in cohesiveness, i.e., no disruption to the gluten network was observed. Relaxation tests showed that the blends with a higher oat content yielded 10 times higher stress values compared to wheat dough. Analysis of the oat–wheat breads showed improvements in nutritional parameters, with slight decreases in the volume and crust color. The crumb showed significant increases in firmness and chewing strength as the amount of oats added increased. Nutritional parameters showed that lipids, dietary fiber, and β-glucans were significantly increased by the addition of oats. Sensory analysis achieved high response rates with good-to-very good ratings on the hedonic scale set. Thus, the addition of oats did not generate rejection by the consumer and could be accepted by them. Breads with wheat and oats showed nutritional improvements with respect to wheat bread, since they have higher dietary fiber content, especially in β-glucans, so they could be considered functional breads.EEA Cesáreo NaredoFil: Astiz, Valentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cesareo Naredo; ArgentinaFil: Guardianelli, Luciano Martín. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Guardianelli, Luciano Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Salinas, María Victoria. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Salinas, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Brites, Carla. Instituto Nacional de Investigação Agrária e Veterinária; PortugalFil: Puppo, María Cecilia. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Puppo, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin

White lupine (Lupinus albus L.) flours for healthy wheat breads: rheological properties of dough and the bread quality

Protein-based foods based on sweet lupine are gaining the attention of industry and consumers on account of their being one of the legumes with the highest content of proteins (28–48%). Our objective was to study the thermal properties of two lupine flours (Misak and Rumbo) and the influence of different amounts of lupine flour (0, 10, 20 and 30%) incorporations on the hydration and rheological properties of dough and bread quality. The thermograms of both lupine flours showed three peaks at 77–78 ◦C, 88–89 ◦C and 104–105 ◦C, corresponding to 2S, 7S and 11S globulins, respectively. For Misak flour, higher energy was needed to denature proteins in contrast to Rumbo flour, which may be due to its higher protein amount (50.7% vs. 34.2%). The water absorption of dough with 10% lupine flour was lower than the control, while higher values were obtained for dough with 20% and 30% lupine flour. In contrast, the hardness and adhesiveness of the dough were higher with 10 and 20% lupine flour, but for 30%, these values were lower than the control. However, no differences were observed for G0 , G00 and tan parameters between dough. In breads, the protein content increased ~46% with the maximum level of lupine flour, from 7.27% in wheat bread to 13.55% in bread with 30% Rumbo flour. Analyzing texture parameters, the chewiness and firmness increased with incorporations of lupine flour with respect to the control sample while the elasticity decreased, and no differences were observed for specific volume. It can be concluded that breads of good technological quality and high protein content could be obtained by the inclusion of lupine flours in wheat flour. Therefore, our study highlights the great technological aptitude and the high nutritional value of lupine flours as ingredients for the breadmaking food industry.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Propiedades fisicoquímicas de harinas de trigo y avena de alta calidad panadera = Physicochemical properties of wheat and oat flours of high technological quality

El pan es un alimento de consumo masivo que puede mejorarse nutricionalmente mediante el agregado de distintos ingredientes. La harina de avena (Avena Sativa L.) con harina de trigo pan de buena calidad industrial se podrían combinar para obtener productos panificados con características aceptables para el consumidor y mejoras nutricionales. El objetivo de este trabajo fue analizar fisicoquímicamente las características de harinas de diferentes variedades de trigo y avena para ser utilizadas en panificación. Para esto se utilizaron tres variedades de trigo pan y nueve variedades de avena, dichos cultivares provistos por la Chacra Experimental INTA- Barrow. Se realizaron distintas pruebas de calidad industrial de granos y harinas y una caracterización nutricional/química de las mismas. Finalmente, se evaluó su vida útil. La calidad de grano del trigo pan, mostró que los tres materiales tuvieron buena performance. Dentro de las características de calidad industrial, B. Meteoro fue superior. Se logró ajustar un protocolo para el tratamiento térmico de los granos de avena y para la determinación de actividad la lipasa de las muestras. La calidad nutricional de las variedades de avena, dieron: valores de contenido de proteína elevados, los contenidos de contenido de ceniza, fibra y lípidos fueron similares a los observados en bibliografía. Los b-glucanos mostraron, en todas las variedades, valores superiores a los descriptos en la bibliografía. El análisis de vida útil de harinas, durante 10 meses de almacenamiento, no mostró evidencias de perdida de vida útil según los indicadores utilizados y los límites definidos por el Codex Alimentarius.Bread is a massive consumption food that can be nutritionally improved by adding different ingredients. Oat flour (Avena sativa L.) in combination with bread wheat (Triticum aestivum L.) flour of good industrial quality, bakery products with acceptable characteristics for the consumer, and nutritional improvements could be obtained. The objective of this work was to analyze the characteristics of flours from different varieties of wheat and oats to be used in baking. Three varieties of bread wheat and nine varieties of oats were used, these cultivars were provided by the INTA Barrow Experimental Field. Different industrial quality tests of grains and flours and a nutritional/chemical characterization were made. Finally, its useful life was evaluated. The grain quality of bread wheat showed that the three materials had a good performance. Within the characteristics of industrial quality, B. Meteoro was the best. It was possible to adjust a protocol for the heat treatment of the oat grains and the determination of the lipase activity of the samples. The oat varieties showed higher protein, ash, fiber, and lipid contents and were similar to those observed in the literature. In all the varieties, higher values of b-glucans were found. The analysis of the shelf life of flours during 10 months of storage did not change according to the indicators used and the limits defined by the Alimentarius Codex.EEA Cesáreo NaredoFil: Astiz, Valentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cesareo Naredo; ArgentinaFil: Salinas, María Victoria. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Salinas, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Puppo, María Cecilia. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Puppo, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Puppo, María Cecilia. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentin

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

Rheological properties of dough obtained from wheat flour with pistachio obtained as a by-product of the oil industry

El objetivo de este trabajo fue estudiar el efecto de la incorporación de harina de pistacho a harina de trigo sobre las propiedades reológicas de masa de trigo. Se utilizaron diferentes niveles de harina de pistacho (HP): 5, 15 y 15%. Una masa sin pistacho fue utilizada como control (C). Ensayos farinográficos y alveográficos, contenido de gluten, humedad (H), actividad acuosa (aw), potencial de hidrógeno (pH), análisis de perfil de textura y ensayos de relajación fueron estudiados sobre las masas. La absorción de agua (Abs), el tiempo de desarrollo (td) y la estabilidad obtenidos del farinograma disminuyeron con el incremento de HP, mientras que el aflojamiento aumentó. Además con el agregado de HP, la tenacidad (P), la extensibilidad (L) y el trabajo de deformación (W) disminuyeron. Los valores de gluten húmedo (GH) y gluten seco (GS) aumentaron con el nivel de pistacho, sin embargo la relación GH/GS disminuyó. La masa C presentó mayor H y pH que las masas con pistacho; ambos parámetros disminuyeron con el nivel de HP utilizado. Sin embargo, no hubo diferencias significativas en la aw entre las diferentes masas. La incorporación de 5% de HP, produjo una masa más blanda y menos consistente pero igualmente adhesiva y elástica que C. Sin embargo, al aumentar el nivel de HP la dureza y elasticidad de las masas aumentó. Los módulos elásticos E1 y E3 obtenidos del ensayo de relajación aumentaron mientras que los tiempos de relajación no se modificaron significativamente con HP. Estos cambios obtenidos en la reología de la masa debido a la presencia de harina de pistacho podrían tener diferentes consecuencias en la calidad del pan.The objective of this work was to study the effect of the incorporation of pistachio flour to wheat flour on the rheological properties of wheat dough. Pistachio flour (HP) levels used were: 5, 15 and 15%, and wheat flour dough was studied as a control sample. Dough were studied by farinographic and alveographic assays, gluten content, moisture (H), water activity (aw), potential of hydrogen (pH); texture profile analysis and relaxation assays were also performed on different dough. The farinographic water absorption (Abs), development time (td) and the stability decreased when pistachio flour was used, whereas degree of softening was increase. In addition, with the addition of HP, tenacity (P), extensibility (L) and deformation work (W) decreased. The values of wet gluten (GH) and dry gluten (GS) increased with the HP. However the GH / GS ratio decreased. Control dough had higher H and pH than dough with pistachio. Both parameters decreased with the level of HP. However, no significant differences in aw between different dough were obtained. The incorporation of 5% HP, produced a softer and less consistent dough but similar adhesiveness and elasticity than C. Nevertheless, with the increase in the level of HP, the dough hardness and elasticity increased. The elastic modules E1 and E3 obtained from the relaxation test also increased while the relaxation times were not significantly modified with HP. These changes obtained in rheology of dough due to the presence of pistachio flour could have different consequences on the bread quality.Centro de Investigación y Desarrollo en Criotecnología de Alimento