A colorimetric assay using tetrazolium salts with an electron mediator to evaluate yeast growth in opaque dispersed systems

Background: traditional microbiological enumeration techniques such as colony count are time consuming. Visual evaluation of turbidity growth lacks objectivity and precision. On the other hand, the accuracy of the spectrophotometric readings can be limited by media opacity and/or additives. In this context, colorimetric methods based on tetrazolium salts are an alternative to traditional methods due to their ability to generate endpoints based on color change. The objective of this study was to develop a colorimetric assay based on two different tetrazolium salts and an electron mediator in order to replace the conventional method of viable plate count or absorbance for microbial growth detection in opaque dispersed systems. Methods: a colorimetric method to evaluate yeast growth in broth and opaque dispersed systems using two tetrazolium salts, 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), 2-(4-Iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT) and an electron mediator, 2-methoxy-1,4-Naphthoquinone (MNQ) was developed. In addition, the minimum inhibitory concentrations against Zygosaccharomyces bailii for natamycin and lemongrass essential oil were determined by the proposed method and compared with those obtained using the conventional broth microdilution and plate count methods.Results: showed that the mixture of INT/MNQ, was more effective than TTC/MNQ. In opaque structure systems, the later showed to be more sensitive than absorbance However, in broth it was as sensitivity as absorbance to detect yeast growth. Besides, the INT/MNQ reagent functioned adequately to determine the minimum inhibitory concentrations of antimicrobials in opaque structured systems. Conclusions: These results demonstrated that the proposed method functioned adequately to determine the minimum inhibitory concentrations of antimicrobials in opaque structured systems showing an excellent agreement with the plate count method and the proposed technique allowed the evaluation of yeast growth with lower population levels than the ones required through absorbance readings. Moreover, this colorimetric method is easy to perform and less time consuming.Fil: Zalazar, Aldana Lourdes. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: González, Malena Mariana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gliemmo, María Fernanda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campos, Carmen Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentin

Microbiological and sensory optimization of the use of essential oils in the formulation of a yacon juice

La acción antimicrobiana de los aceites esenciales (AEs) y su combinación con otros factores de estrés microbiano permiten su uso en la formulación de jugos con el fin de extender su vida útil y de responder a la demanda actual de alimentos seguros y naturales. La principal causa de deterioro de jugos ácidos es la inestabilidad microbiológica debido a la acción de levaduras resistentes, como Zygosaccharomyces bailii. En este trabajo se seleccionaron varios AEs por su acción inhibitoria frente a Z. bailii, se optimizó la elaboración de nanoemulsiones de los aceites seleccionados, se estudió su estabilidad, se adicionaron a la formulación de un jugo de yacón y se estudió su interacción con otros aditivos como ácido cítrico y xilitol. Se comenzó con el estudio del efecto de ácidos orgánicos y del xilitol sobre el desarrollo de la levadura y se observó que el ácido cítrico fue el más efectivo y que el descenso del pH a 4,00 redujo el crecimiento independientemente de la presencia de xilitol. El AE de corteza de canela (CC) mostró mayor actividad inhibitoria seguido por los AE de hojas de canela (CH), lemongrass (LG) y menta (M). Se obtuvo una nanoemulsion estable de CH con un homogeneizador de alta velocidad, mientras que nanoemulsiones estables de CC, LG y M fueron obtenidas por ultasonido. El tamaño de gota de las nanoemulsiones disminuyó con el incremento del nivel de Tween®80. Todas las nanoemulsiones mostraron acción antimicrobiana frente a Z. bailii a pH 4,00, obteniéndose mínimas concentraciones inhibitorias (MCI) entre 156,3 y 1250,0 ppm, dependiendo del AE. El aumento del tiempo de ultrasonicación no afectó el tamaño de la gota, la estabilidad física y la MCI de las nanoemulsiones, pero el crecimiento de la levadura se incrementó ligeramente debido a la ultrasonicación. El uso conjunto de las nanoemulsiones de LG y CC mostró una interacción aditiva frente al crecimiento de Z. bailii. Se optimizó la obtención de jugo de yacón, seleccionando un tratamiento de 60 seg-90°C para minimizar el desarrollo de pardeamiento y reducir la flora nativa. En el jugo, la nanoemulsion de LG presentó mayor acción inhibitoria frente a Z. bailii, fue más estable al tratamiento térmico y sensorialmente más aceptable que la de CC. En base a ello, se formuló un jugo de yacón de pH 4,00, conteniendo 20,0% xilitol y 937,5 ppm de nanoemulsion de LG, el cual fue microbiológicamente estable a 5°C por 28 días. Una dilución 1/4 de este jugo permitió obtener una bebida aceptable por consumidores. La optimización microbiológica y sensorial del uso de AEs en la formulación de jugo de yacón aporta compuestos naturales con acción antimicrobiana y mejora la calidad de estos alimentos.The antimicrobial action of essential oils (EOs) and their combination with other microbial stress factors allow their use in the formulation of juices in order to extend their shelf life and respond to the current demand for safe and natural foods. The main cause of deterioration of acidic juices is the microbiological instability due to the action of resistant yeasts, such as Zygosaccharomyces bailii. In this work, several EOs were selected for their inhibitory action against Z. bailii, the production of nanoemulsions of the selected oils was optimized, their stability was studied, they were added to the formulation of a yacon juice and their interaction with others additives was studied like citric acid and xylitol. It started with the study of the effect of organic acids and xylitol on yeast development and it was observed that citric acid was the most effective and that lowering the pH to 4,00 reduced growth independently of the presence of xylitol. The cinnamon bark EO (CB) showed greater inhibitory activity followed by the EO of cinnamon leaves (CL), lemongrass (LG) and mint (M). Stable CC nanoemulsion was obtained with a high speed homogenizer, while stable CL, LG and M nanoemulsions were obtained by ultasound. Nanoemulsions droplet size decreased with increasing Tween®80 level. All nanoemulsions showed antimicrobial action against Z. bailii at pH 4,00, obtaining minimal inhibitory concentrations (MIC) between 156,3 and 1250,0 ppm, depending on the EO. Increasing ultrasonication time did not affect the droplet size, physical stability, and MIC of the nanoemulsions, but yeast growth was slightly increased due to ultrasonication. The combined use of the LG and CB nanoemulsions showed an additive interaction against the growth of Z. bailii. Obtaining yacon juice was optimized, selecting a treatment of 60 sec-90°C to minimize the development of browning and reduce the native flora. In the juice, the LG nanoemulsion showed a greater inhibitory action against Z. bailii, it was more stable to heat treatment and sensorially more acceptable than that of CB. Based on this, a yacon juice of pH 4,00 was formulated, containing 20,0% xylitol and 937,5 ppm of LG nanoemulsion, which was microbiologically stable at 5°C for 28 days. A 1/4 dilution of this juice allowed obtaining a drink acceptable to consumers. The microbiological and sensorial optimization of the use of EOs in the formulation of yacon juice provides natural compounds with antimicrobial action and improves the quality of these foods.Fil: González, Malena Mariana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Lemongrass and cinnamon oil nanoemulsions: Formulation and study of their physical stability and activity against Zygosaccharomyces bailii

The optimal conditions for elaborating oil/water nanoemulsions of lemongrass (LG), cinnamon bark (CB) and cinnamon leaves (CL) essential oils and their antimicrobial activity against Zygosaccharomyces bailii at pH 4.00 were studied. The effect of the emulsification methodology on the physical stability and antimicrobial activity of the nanoemulsions were also evaluated. Furthermore, the sensory impact of nanoemulsions added to an apple juice was tested. LG and CL nanoemulsions were elaborated by ultrasonication and CB nanoemulsion, by high-speed homogenization. They were stable for at least 120 days at 25 °C. They exhibited antimicrobial activity against Z. bailii being CB the most effective since it showed the smallest MIC value (156.3 mg/l), followed by LG (468.8 mg/l) and CL (1250.0 mg/l). A slight increase in growth rate was observed due to ultrasonication. An additive interaction in relation to the inhibitory effect between LG and CB nanoemulsions against Z. bailii was observed. While nanoemulsions obtained would be used as natural antimicrobial agents in food and beverage products, only LG nanoemulsion at MIC concentration diluted was acceptable in juice showing the sensory impact of essential oils on foods.Fil: González, Malena Mariana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; ArgentinaFil: Zalazar, Aldana Lourdes. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; ArgentinaFil: Pedreira, Julieta Denise. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Campos, Carmen Adriana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Quimicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Quimicos.; ArgentinaFil: Gliemmo, María Fernanda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Quimicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Quimicos.; Argentin

Effect of xantham gum, steviosides, clove, and cinnamon essential oils on the sensory and microbiological quality of a low sugar tomato jam

The partial or total decrease of sugar content in the formulation of jams affects their physical, chemical and microbiological stability. In order to minimize these technological problems, we studied the effect of xanthan gum (XG), steviosides, cinnamon (CO), and clove (CLO) essential oils on the sensory and microbiological quality of a low sugar tomato jam. Levels of 0.250 g/100 g steviosides and 0.450 g/100 g XG showed maximum score of overall acceptability of jam. The combination of essential oils produced synergistic and additive effects in vitro on growth of Z. bailii and Z. rouxii, respectively. However, in the jam, CO was more effective and CLO did not modify the CO action. Cell surface was one of the sites of action of CO since a decrease in yeast cell surface hydrophobicity was observed. From the microbiological and sensory points of view, 0.0060 g/100 g CO showed the maximum score of jam overall acceptability and did not cause yeast inactivation but it could be useful as an additional stress factor against yeast post – process contamination. The adequate levels of XG, steviosides, and CO can improve the quality of a low sugar jam formulation.Fil: Gliemmo, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Montagnani, María A.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; ArgentinaFil: Schelegueda, Laura Inés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González, Malena Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Campos, Carmen Adriana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Comunicación política y nuevos territorios digitales

Entrevistas en el Estudio es una serie audiovisual que convoca a referentes de diversos ámbitos de la vida político, social, económica y comunitaria, entre otros, para que compartan sus saberes y experiencias sobre temáticas variadas. La presente entrevista audiovisual denominada Comunicación política y nuevos territorios digitales cuenta con la participación de la docente y comunicadora María Fernanda Ruiz; quien a lo largo de 5 piezas audiovisuales aborda la dimensión política de la comunicación, resaltando la importancia de la territorialidad digital como un espacio de disputa simbólica, política, e ideológica; además de referirse a cuestiones como la soberanía tecnológica y la filosofía de la técnica. Estos contenidos comunicacionales están destinados a la comunidad y fueron coproducidos por la Secretaría Académica, la Cátedra de Gestión Popular de Medios Públicos y Comunitarios, la Tecnicatura en Comunicación Popular y la Agrupación Rodolfo Walsh de la FPyCS- UNLP.Para acceder a la lista de reproducción con todas las entrevistas, hacer clic en "Enlace externo".Facultad de Periodismo y Comunicación Socia

Informe ampliado: efectos socioeconómicos y culturales de la pandemia COVID-19 y del aislamiento social, preventivo y obligatorio en los Pueblos Indígenas en Argentina -Segunda etapa, junio 2020-

A partir de la pandemia generada por el COVID-19, con el consiguiente Aislamiento Social Preventivo y Obligatorio (ASPO) dispuesto a partir del 20/03/2020 y demás acciones implementadas desde el Estado nacional argentino, un conjunto de equipos, instituciones, investigadores, becaries y tesistas de diferentes ámbitos del país, nos agrupamos con el objetivo de elaborar un informe acerca de las consecuencias e impactos socioeconómicos y culturales que atraviesan los pueblos indígenas con los que trabajamos en las regiones Metropolitana, Pampeana, Noroeste, Noreste, Cuyo y Patagonia. En una primera instancia, más de 30 autores, participaron en la elaboración de un informe (1er etapa) presentado el 15 de abril de 20201 . En esta segunda etapa, con más de 100 integrantes de diferentes ámbitos académicos del país, se amplió lo abordado a partir de la actualización y profundización de las problemáticas y situaciones que experimentan un conjunto de diversas comunidades y pueblos originarios –qom, mbya, moqoit, mapuche, guaraní, tupí guaraní, avá guaraní, kolla, diaguita, diaguita-calchaquí, wichí, huarpe, quechua, aymara, nivaclé, tonokote, omaguaca, tastil, günün a küna, comechingón, comechingón-camiare, ocloya, iogys, chané, tapiete, chorote, chulupi, sanavirón, ranquel, wehnayek, atacama, lule, quilmes, mapuche-pehuenches, tehuelches, mapuche-tehuelches, selk‘nam, haush y selk‘nam-haush-.Valdata, Marcela. Universidad Nacional de Rosario. Facultad de Humanidades y Artes. Centro de Estudios Aplicados a Problemáticas Socioculturales. Rosario; Argentin

First large-scale study reveals important losses of managed honey bee and stingless bee colonies in Latin America

International audienceOver the last quarter century, increasing honey bee colony losses motivated standardized large-scale surveys of managed honey bees ( Apis mellifera ), particularly in Europe and the United States. Here we present the first large-scale standardized survey of colony losses of managed honey bees and stingless bees across Latin America. Overall, 1736 beekeepers and 165 meliponiculturists participated in the 2-year survey (2016–2017 and 2017–2018). On average, 30.4% of honey bee colonies and 39.6% of stingless bee colonies were lost per year across the region. Summer losses were higher than winter losses in stingless bees (30.9% and 22.2%, respectively) but not in honey bees (18.8% and 20.6%, respectively). Colony loss increased with operation size during the summer in both honey bees and stingless bees and decreased with operation size during the winter in stingless bees. Furthermore, losses differed significantly between countries and across years for both beekeepers and meliponiculturists. Overall, winter losses of honey bee colonies in Latin America (20.6%) position this region between Europe (12.5%) and the United States (40.4%). These results highlight the magnitude of bee colony losses occurring in the region and suggest difficulties in maintaining overall colony health and economic survival for beekeepers and meliponiculturists

Search for Scalar Diphoton Resonances in the Mass Range 65−60065-600 GeV with the ATLAS Detector in pppp Collision Data at s\sqrt{s} = 8 TeVTeV

A search for scalar particles decaying via narrow resonances into two photons in the mass range 65–600 GeV is performed using $20.3\text{}\text{}{\mathrm{fb}}^{-1}$ of $\sqrt{s}=8\text{}\text{}\mathrm{TeV}$ $pp$ collision data collected with the ATLAS detector at the Large Hadron Collider. The recently discovered Higgs boson is treated as a background. No significant evidence for an additional signal is observed. The results are presented as limits at the 95% confidence level on the production cross section of a scalar boson times branching ratio into two photons, in a fiducial volume where the reconstruction efficiency is approximately independent of the event topology. The upper limits set extend over a considerably wider mass range than previous searches

Search for Higgs and ZZ Boson Decays to J/ψγJ/\psi\gamma and Υ(nS)γ\Upsilon(nS)\gamma with the ATLAS Detector

A search for the decays of the Higgs and $Z$ bosons to $J/\psi\gamma$ and $\Upsilon(nS)\gamma$ ($n=1,2,3$) is performed with $pp$ collision data samples corresponding to integrated luminosities of up to $20.3\mathrm{fb}^{-1}$ collected at $\sqrt{s}=8\mathrm{TeV}$ with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above expected backgrounds and 95% CL upper limits are placed on the branching fractions. In the $J/\psi\gamma$ final state the limits are $1.5\times10^{-3}$ and $2.6\times10^{-6}$ for the Higgs and $Z$ bosons, respectively, while in the $\Upsilon(1S,2S,3S)\,\gamma$ final states the limits are $(1.3,1.9,1.3)\times10^{-3}$ and $(3.4,6.5,5.4)\times10^{-6}$, respectively

Search for Scalar-Charm pair production in pp collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb$^{-1}$ of pp collisions at $\sqrt{s}=8$ TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c-quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal supersymmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper limits are obtained in the scalar-charm-neutralino mass plane such that, for neutralino masses below 200 GeV, scalar-charm masses up to 490 GeV are excluded