Differentiation Between Ripening Stages of Iberian Dry-Cured Ham According to the Free Amino Acids Content

In this paper, the differentiation of three ripening stages, postsalting, drying, and cellar, of Iberian dry-cured ham has been carried out according to their free amino acids contents. Eighteen L-amino acids, alanine, 2-aminobutanoic acid, aspartic acid, cysteine, glutamine, glycine, histidine, hydroxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, and valine have been determined by gas chromatography with derivatization with N,O-bis(trimethylsilyl)-trifluoroacetamide. Gas chromatography-mass spectrometry was used to confirm the presence of the eighteen amino acids in the ham samples, and gas chromatography using a DB-17HT column and flame ionization detector was used for quantitative determination. Extraction with a mixture methanol-acetonitrile has been carried out, achieving recoveries in the range 52-164%. Methimazole was used as internal standard. Limits of detection ranged between 7.0 and 611.7 mg·kg-1. Free amino acids have been used as chemical descriptors to differentiate between the ripening stages. Principal component analysis and linear discriminant analysis have been used as chemometric techniques, achieving complete differentiation between the ripening stages. Alanine, tyrosine, glutamine, proline, 2-aminobutanoic acid, cysteine, and valine were the most differentiating amino acids.Junta de Andalucía the project P09-AGR-0478

A Practical Example on Uncertainty Evaluation: Spectrophotometric Determination of pKa

A practical example, focused on the evaluation of uncertainty and its propagation in spectrophotometric determination of ionization constants, is proposed in this work. The Hildebrand - Reilley method has been used in order to calculate the acetaminofen pKa value. After applying this method a linear relationship between pH and a logarithmic term depending on absorbances, was established. The value of pKa is obtained as the intercept of this straight-line and its error is evaluated from least squares calculations. As errors in both variables have to be considered, weighted least squares (WLS) must be used. The evaluation of uncertainty in pH measurements was carried out according to IUPAC recommendations in the case of glass electrode with two calibration standards. The uncertainty contributions of absorbance and work standard concentration, evaluated according to GUM, have been propagated to Hildebrand – Reilley expression in order to obtain the errors to be used in WLS calculations. Due to the different topics included in this tutorial, it can be considered as a useful tool for training people learning about the evaluation of uncertainty in measurements and its propagation

Fitting chemical data with Excel: A practical tutorial

La revista es Open AccessExcel es un programa de hojas de cálculo incluido en Microsoft Office utilizado en un gran número de empresas públicas y privadas en el mundo. Este programa permite realizar muchas operaciones, como el ajuste de datos experimentales a funciones matemáticas. Estas tareas son comunes en los laboratorios químicos, y parece razonable entrenar a los profesionales en el uso de estas herramientas. En este trabajo se han estudiado 4 metodologías de ajuste usando este programa, resolviendo algunos ejemplos prácticos de datos químicos, considerando sus ventajas y desventajas.Excel is spreadsheets software included in Microsoft Office that is used in a high number of public and private companies all over the world. This program allows carrying out many operations such as fitting experimental data to mathematical functions. These tasks are usually performed in chemical laboratories and, accordingly, it seems reasonable to train professionals in the use of these tools. In this work, four fitting methodologies using this program have been studied by solving some practical examples of chemical data, considering their advantages and disadvantage

Implicaciones de los abejorros (Bombus spp.) en la dispersión del virus del mosaico del pepino dulce (Pepino Mosaic Virus) en cultivos de tomate

[SPA] Desde 1999 el virus del mosaico del pepino dulce (Pepino Mosaic Virus, PepMV) afecta el cultivo del tomate en varios países europeos. Produce abullonado, mosaicos y filiformismo en las hojas jóvenes y jaspeado y pardeamiento en los frutos. Se transmite fácilmente por contacto entre plantas y mecánicamente por las manipulaciones de las labores culturales (desbrotado, entutorado, etc.). Se han realizado ensayos para conocer las posibles implicaciones de los abejorros polinizadores en la dispersión del virus en los cultivos de invernadero, donde mayoritariamente se utilizan Bombus terrestris y B. canariensis. En primavera, a las 4 semanas de haber puesto plantas de tomate sanas en un invernadero comercial contaminado de PepMV y con abejorros, se contaminaron las primeras plantas y a las 7-8 semanas se habían contaminado todas, para niveles medios de l'l a 3'0 flores visitadas/plantas y semana. Mediante test ELISA con suero de PepMV se ha detectado el virus en las patas (con o sin polen), en la cabeza y en el abdomen de los abejorros, siendo en las patas y en el polen de las escopas donde más frecuentemente se ha detectado. Al inocular, en condiciones controladas, plantas de tomate con extractos del cuerpo (incluido el polen adherido) de los abejorros recolectados en invernaderos de tomate contaminados de PepMV, se obtuvieron infecciones y síntomas en más del 85% de los casos. No se conocen con exactitud los mecanismos de la transmisión que intervienen en la dispersión del virus por Bombus spp., ya que tampoco se conoce con precisión el comportamiento etológico de los abejorros en el cultivo del tomate, habiéndose puesto de manifiesto que pueden transportar partículas infectivas del PepMV.[ENG] Since 1999, Pepino Mosaic Virus (PepMV) is a new virus disease for tomato crops of several european countries. It produces mosaics and deformations on the leaves and mottled and brown fruits on infected tomato plants. It is easily transmitted by plant contact and mechanically by plant manipulation from cultural practices (staking and prunning plants, etc.). Assays have been carried out to determine the potential implications of bombus bees on the spread of the disease on greenhouse tomato crop where Bombus terrestris and B. canariensis were used. In spring, healthy plants were transplanted in a commercial greenhouse with PepMV infested plants and bombus bees used as pollinators. The first plants with PepMV symptoms were observed four weeks after transplant and after seven to eight weeks all plants were infested. Bombus bees were recorded to visit flowers on each plant 1.3-3.0 times a week on average. PeMV was detected by ELISA using PepMV antisera on legs (with and without pollen), head and abdomen of bombus bees. PeMV was detected more frequently on legs. When healthy tomato plants were inoculated with body extract of PepMV contaminated bombus bees more infections and symptoms were observed in more than 85% of the cases. The transmission processes implicated on virus spread by bombus bees are not well known, nor is it precisely bombus bees behaviour on tomato crops. In this work transmission of PepMV particles by bombus bees have been demonstrated.El trabajo se encuadra en el ámbito de actuación del proyecto de investigación AGL 2000-1651-C03-02 financiado por el Ministerio de Ciencia y Tecnología. Expresamos el agradecimiento a los productores de tomate, en particular a la empresa DURAN H08 y a los asociados a las cooperativas COARA y COEXMA, por su colaboración

Differentiation between Ripening Stages of Iberian Dry-Cured Ham According to the Free Amino Acids Content.

In this paper, the differentiation of three ripening stages, postsalting, drying, and cellar, of Iberian dry-cured ham has been carried out according to their free amino acids contents. Eighteen L-amino acids, alanine, 2-aminobutanoic acid, aspartic acid, cysteine, glutamine, glycine, histidine, hydroxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, and valine have been determined by gas chromatography with derivatization with N,O-bis(trimethylsilyl)-trifluoroacetamide. Gas chromatography–mass spectrometry was used to confirm the presence of the eighteen amino acids in the ham samples, and gas chromatography using a DB-17HT column and flame ionization detector was used for quantitative determination. Extraction with a mixture methanol-acetonitrile has been carried out, achieving recoveries in the range 52–164%. Methimazole was used as internal standard. Limits of detection ranged between 7.0 and 611.7 mg·kg−1. Free amino acids have been used as chemical descriptors to differentiate between the ripening stages. Principal component analysis and linear discriminant analysis have been used as chemometric techniques, achieving complete differentiation between the ripening stages. Alanine, tyrosine, glutamine, proline, 2-aminobutanoic acid, cysteine, and valine were the most differentiating amino acidsThis study was supported by Junta de Andalucía through the project P09-AGR-04789

Differentiation between Ripening Stages of Iberian Dry-Cured Ham According to the Free Amino Acids Content

14 Páginas.-- 6 Figuras.-- 7 TablasIn this paper, the differentiation of three ripening stages, postsalting, drying, and cellar, of Iberian dry-cured ham has been carried out according to their free amino acids contents. Eighteen L-amino acids, alanine, 2-aminobutanoic acid, aspartic acid, cysteine, glutamine, glycine, histidine, hydroxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, and valine have been determined by gas chromatography with derivatization with N,O-bis(trimethylsilyl)-trifluoroacetamide. Gas chromatography–mass spectrometry was used to confirm the presence of the eighteen amino acids in the ham samples, and gas chromatography using a DB-17HT column and flame ionization detector was used for quantitative determination. Extraction with a mixture methanol-acetonitrile has been carried out, achieving recoveries in the range 52–164%. Methimazole was used as internal standard. Limits of detection ranged between 7.0 and 611.7 mg·kg−1. Free amino acids have been used as chemical descriptors to differentiate between the ripening stages. Principal component analysis and linear discriminant analysis have been used as chemometric techniques, achieving complete differentiation between the ripening stages. Alanine, tyrosine, glutamine, proline, 2-aminobutanoic acid, cysteine, and valine were the most differentiating amino acidsThis study was supported by Junta de Andalucía through the project P09-AGR-04789.Peer reviewe

Implicaciones de los abejorros (Bombus spp.) en la dispersión del virus del mosaico del pepino dulce (Pepino Mosaci Virus) en cultivos de tomate

Desde 1999 el virus del mosaico del pepino dulce (Pepino Mosaic Virus, PepMV) afecta el cultivo del tomate en varios países europeos. Produce abullonado, mosaicos y filiformismo en las hojas jóvenes y jaspeado y pardeamiento en los frutos. Se transmite fácilmente por contacto entre plantas y mecánicamente por las manipulaciones de los labores culturales (desbrotado, entutorado, etc.). Se han realizado ensayos para conocer las posibles implicaciones de los abejorros polinizadores en la dispersión del virus de los cultivos en invernadero, donde mayoritariamente se utilizan Bombus terrestris y B. canariensis. En primavera, a las 4 semanas de haber puesto plantas de tomate sanas en un invernadero comercial contaminado de PepMV y con abejorros se contaminaron las primeras plantas y a las 7-8 semanas se habían contaminado todas, para niveles medios de 1¿1 a 3¿0 flores visitadas/plantas y semana. Mediante test ELISA con suero de PepMV se ha detectado el virus en las patas (con o sin polen), en la cabeza y en el abdomen de los abejorros, siendo en las patas y en el polen de escopas donde más frecuentemente se ha detectado. Al inocular, en condiciones controladas, plantas de tomate con extractos del cuerpo (incluido el polen adherido) de los abejorros recolectados en invernaderos de tomate contaminados de PepMV, se obtuvieron infecciones y síntomas en más del 85% de los casos. No se conocen con exactitud los mecanismos de la transmisión que intervienen en la dispersión del virus por Bombus spp., ya que tampoco se conoce con precisión el comportamiento etológico de los abejorros en el cultivo del tomate, habiéndose puesto de manifiesto que pueden transportar partículas infectivas del PepMV