Comparación de técnicas analíticas usadas para la determinación de la distribución posicional de ácidos grasos en los triacilglicéridos. Relación con el punto de fusión y la dureza de la grasa de cerdo

This study was conducted to compare two of the most widely used methods for the determination of the positional distribution of fatty acids within the triacylglycerol molecules from fats of animal origin. Method A involves incubation of the triacylglycerol fraction with an aqueous suspension of the lipase enzyme, separation of the reaction products by thin-layer chromatography (TLC), and analysis of fatty acid methyl esters by gas-liquid chromatography. Method B eliminates the need for TLC. This technique makes use of the fact that methanolic-NaOH methylates only fatty acids esterified to glycerol. Our results demonstrated that method A data were in line with previous literature. Additionally, method A showed good correlations between fatty acid positional distribution and fat melting point and hardness. However, method B showed an underestimation of palmitic acid and lacked correlation with selected physical properties.Este estudio se realizó con el objetivo de comparar los dos métodos más comúnmente utilizados en la determinación de la distribución posicional de ácidos grasos en las moléculas de triacilglicéridos de grasas de origen animal. El método A consiste en la incubación de los triacilglicéridos en una suspensión acuosa de la enzima lipasa, la separación de los productos por cromatografía de capa fina (TLC), y el posterior análisis de los ésteres metílicos de ácidos grasos de cada fracción mediante cromatografía gas-líquido. El método B elimina la separación por TLC. Este método se basa en que la metilación básica (NaOH) únicamente metila los ácidos grasos esterificados al glicerol. Cuando analizamos grasa subcutánea de cerdo, nuestros resultados demuestran que los datos obtenidos con el método A estuvieron en concordancia con resultados publicados anteriormente. Además el método A mostró una buena correlación entre la distribución de los ácidos grasos y el punto de fusión y dureza de las grasas analizadas. Sin embargo, el método B condujo a una subestimación del ácido palmítico y a resultados carentes de correlación con las propiedades físicas citadas

Computer Vision and Metrics Learning for Hypothesis Testing: An Application of Q-Q Plot for Normality Test

This paper proposes a new procedure to construct test statistics for hypothesis testing by computer vision and metrics learning. The application highlighted in this paper is applying computer vision on Q-Q plot to construct a new test statistic for normality test. Traditionally, there are two families of approaches for verifying the probability distribution of a random variable. Researchers either subjectively assess the Q-Q plot or objectively use a mathematical formula, such as Kolmogorov-Smirnov test, to formally conduct a normality test. Graphical assessment by human beings is not rigorous whereas normality test statistics may not be accurate enough when the uniformly most powerful test does not exist. It may take tens of years for statistician to develop a new and more powerful test statistic. The first step of the proposed method is to apply computer vision techniques, such as pre-trained ResNet, to convert a Q-Q plot into a numerical vector. Next step is to apply metric learning to find an appropriate distance function between a Q-Q plot and the centroid of all Q-Q plots under the null hypothesis, which assumes the target variable is normally distributed. This distance metric is the new test statistic for normality test. Our experimentation results show that the machine-learning-based test statistics can outperform traditional normality tests in all cases, particularly when the sample size is small. This study provides convincing evidence that the proposed method could objectively create a powerful test statistic based on Q-Q plots and this method could be modified to construct many more powerful test statistics for other applications in the future

Annama H chondrite-Mineralogy, physical properties, cosmic ray exposure, and parent body history

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7-8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 +/- 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30-40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The Be-10 concentration indicates a recent (3-5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30-35 cm pre-entry radius.Peer reviewe

Nanoindenting the Chelyabinsk meteorite to learn about impact deflection effects in asteroids

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids (NEAs). Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young's modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and therefore higher values imply more efficient impacts. In the Chelyabinsk meteorite the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and therefore increase the momentum multiplication. These results are relevant in the context of a future mission to test asteroid deflection, currently being studied by ESA and NASA: the Asteroid Impact and Deflection Assessment (AIDA) mission

Natural history of G ynaikothrips uzeli (Thysanoptera, Phlaeothripidae) in galls of Ficus benjamina (Rosales, Moraceae)

ABSTRACT Galls induced by thrips are simple structures when compared to those of other groups of arthropods, and little is known regarding many of their aspects. This study aimed to investigate aspects of the natural history of Gynaikothrips uzeli Zimmermann, 1900 in galls of Ficus benjamina L., 1753 using seasonal sampling (summer and winter). Twenty trees were sampled and divided into quadrants. From each of them, five galls were collected, forming a total of 400 galls per collection. Thrips showed greater abundance at higher temperatures (25.7°C) and no precipitation. Sex ratio was biased towards females (0.022 males per female), pointing to an inbred mating structure. Arthropod fauna associated with galls was more abundant (N=798) in winter, and it included representatives of the orders Hemiptera, Hymenoptera, Araneae, Coleoptera, Neuroptera, Psocoptera, Thysanoptera, Diptera and Blattodea

NMR-detection of methylamine compounds in Atlantic salmon (Salmo salar) subjected to E-beam irradiation

Exudates and muscles from Atlantic salmon samples, subjected to different E-beam irradiation treatments, have been employed to monitor, through 1 H NMR analysis, the effects of irradiation dose and storage time on methylamine compounds. The three methylamines identified in the spectra, [trimethylamine N-oxide (TMAO), trimethylamine (TMA) and monomethylamine (MMA)], showed significant differences between non-irradiated and irradiated samples. MMA was present in all irradiated samples, and absent from non-irradiated ones. Furthermore, MMA signal intensity was well correlated with the irradiation dose applied and was stable during storage time. Therefore, MMA could be an effective indicator of irradiation in samples of salmon

Raman spectroscopy study of the structural effect of microbial transglutaminase on meat systems and its relationship with textural characteristics

Raman spectroscopy and texture analysis (TPA) studies were carried out to determine the effect of adding different levels of microbial transglutaminase (MTGase) to meat systems. This addition produced a significant (p < 0.05) increase in hardness, springiness and cohesiveness in the meat systems. Raman spectroscopy analysis revealed the occurrence of secondary structural changes in meat proteins due to MTGase. Modifications in the amide I (1650-1680 cm-1) and amide III (1200-1300 cm-1) regions indicated a significant (p < 0.05) decrease in α-helix content, accompanied by a significant (p < 0.05) increase in β-sheets and turns due to the addition of the enzyme to meat systems. Significant (p < 0.05) correlations were found between these secondary structural changes in meat proteins and the textural properties (hardness, adhesiveness, springiness and cohesiveness) of meat systems. © 2007 Elsevier Ltd. All rights reserved.Peer Reviewe

Lack of growth of Listeria monocytogenes and Staphylococcus aureus in temperature abuse of E-beam treated ready-to-eat (RTE) cooked ham

The behaviour of Listeria monocytogenes and Staphylococcus aureus in vacuum-packed cooked ham slices treated with an electron beam and stored at 4, 7 and 10 °C was investigated. Cooked ham slices were inoculated with L. monocytogenes and S. aureus and electron beam treated at 2 and 3 kGy. After treatment, a long temperature-dependent death phase was observed, followed by growth at a slower rate than in untreated samples. Assuming a hypothetical load of 10 cells/g or cm2 of L. monocytogenes and S. aureus as an original contamination in an industrial situation, an E-beam treatment of vacuum-packed cooked ham slices at 2 kGy guarantees the microbiological safety of the product along its shelf life, even if a noticeable temperature (10 °C) abuse occur during its storage period. Likewise, the E-beam treatment gave rise to a substantial increase of the RTE cooked ham shelf life off-sensory features associated to the spoilage only were detected in non-treated samples (controls) after 8 and 18 days of storage at 10 °C and 7 °C, respectively. © 2010 Elsevier Ltd

Plasma powder as cold-set binding agent for meat system: Rheological and Raman spectroscopy study

The effect of plasma powder addition, with or without NaCl, to meat emulsion has been studied. The Raman spectroscopy and rheological characteristics of four model systems [plasma powder (PP), rehydrated plasma powder (PPW), meat emulsion (ME) and meat emulsion with addition of rehydrated plasma powder (MEPPW)] were evaluated. The MEPPW system showed the highest (p < 0.05) hardness, springiness and breaking force. A decrease (p < 0.05) in hardness and an increase (p < 0.05) in adhesiveness with the addition of NaCl were observed in the ME and MEPPW systems. The addition of PPW to meat emulsion (MEPPW system) produced a decrease of α-helix and an increase of turns and unordered structure (p < 0.05). A decrease in the 1450 cm-1 and 2935 cm-1 band intensities (related with hydrophobic interactions) associated to PPW addition to ME was observed. Correlations (p < 0.05) between meat protein structural changes and rheological properties of meat systems were found. © 2008 Elsevier Ltd. All rights reserved.Peer Reviewe