Computational estimation of soybean oil adulteration in Nepalese mustard seed oil based on fatty acid composition

The experiment was carried out for the computational estimation of soybean oil adulteration in the mustard seed oil using chemometric technique based on fatty acid composition. Principal component analysis and K-mean clustering of fatty acid composition data showed 4 major mustard/rapeseed clusters, two of high erucic and two of low erucic mustard type. Soybean and other possible adulterants made a distinct cluster from them. The methodology for estimation of soybean oil adulteration was developed based on weighted least square error principle using Microsoft Excel Solver program. This principle was successfully validated on the real soybean mustard oil blends. Moreover, the method was further evaluated on the 4000 training set and 3999 validation set simulated blends of mustard and soybean oil based on 212 fatty acid composition data. The blending was simulated with data from different literature from different part of the world along with data collected in our laboratory. The simulated blend consisted of random mixture of up to 16 samples. These are more extreme conditions than that can usually be expected in real scenario

Influence of oxidized oils on digestibility of caseins in O/W emulsions

The impact of lipid oxidation on protein modifications in emulsions and the consequences on protein digestibility remains unclear. In this study, this impact is evaluated in casein (6 mg mL(-1)) based emulsions containing oxidized soybean or fish oil (3%) in presence (0.3%) or absence of the emulsifier Tween 20. Emulsions are prepared using oils at three oxidation levels and subsequently the impact on protein digestibility is evaluated after 24 h incubation at 4 degrees C. Remarkably, protein digestibility increases in emulsions containing medium and highly oxidized fish oil: 70 +/- 0.4% and 73 +/- 0.4% of the proteins are digested, respectively, whereas protein digestibility in emulsions containing low oxidized fish oil amounted to 63 +/- 0.4%. Protein digestibility in emulsions containing soybean oil stabilized by Tween 20 is not influenced by the oxidation level of the oil used. A remarkable tendency is observed for the malondialdehyde content of the emulsions depending on the presence of Tween 20. For soybean oil based emulsions, malondialdehyde concentrations are consistently higher in the presence of Tween 20. On the other hand, for the fish oil based emulsions an opposite trend is observed, except at the highest oxidation level evaluated, for which no significant differences can be detected. It is concluded that the composition of the interface in emulsions depends strongly upon the degree of oil oxidation and the presence of other emulsifiers. If the oil is more oxidized, less protein is present in the interface restricting the impact of lipid oxidation products on the proteins and hence their digestibility

Deriving physical parameters of unresolved star clusters III. Application to M31 PHAT clusters

This study is the third of a series that investigates the degeneracy and stochasticity problems present in the determination of physical parameters such as age, mass, extinction, and metallicity of partially resolved or unresolved star cluster populations situated in external galaxies when using broad-band photometry. This work tests the derivation of parameters of artificial star clusters using models with fixed and free metallicity for the WFC3+ACS photometric system. Then the method is applied to derive parameters of a sample of 203 star clusters in the Andromeda galaxy observed with the HST. Following Papers I \& II, the star cluster parameters are derived using a large grid of stochastic models that are compared to the observed cluster broad-band integrated WFC3+ACS magnitudes. We derive the age, mass, and extinction of the sample of M31 star clusters with one fixed metallicity in agreement with previous studies. Using artificial tests we demonstrate the ability of the WFC3+ACS photometric system to derive the metallicity of star clusters. We show that the metallicity derived using photometry of 36 massive M31 star clusters is in a good agreement with the metallicity previously derived using spectroscopy taken from literature.Comment: 8 pages, 9 figures, published in Astronomy and Astrophysic

Deriving physical parameters of unresolved star clusters. I. Age, mass, and extinction degeneracies

Context. Stochasticity and physical parameter degeneracy problems complicate the derivation of the parameters (age, mass, and extinction) of unresolved star clusters when using broad-band photometry. Aims. We develop a method to simulate stochasticity and degeneracies, and to investigate their influence on the accuracy of derived physical parameters. Then we apply it to star cluster samples of M31 and M33 galaxies. Methods. Age, mass and extinction of observed star clusters are derived by comparing their broad-band UBVRI integrated magnitudes to the magnitudes of a large grid of star cluster models with fixed metallicity Z=0.008. Masses of stars for a cluster model are randomly sampled from the initial mass function. Models of star clusters from the model grid, which have all of their magnitudes located within 3 observational errors from the magnitudes of the observed cluster, are selected for the computation of its age, mass, and extinction. Results. In the case of the M31 galaxy, the extinction range is wide and the age-extinction degeneracy is strong for a fraction of its clusters. Because of a narrower extinction range, the age-extinction degeneracy is weaker for the M33 clusters. By using artificial cluster sample, we show that age-extinction degeneracy can be reduced significantly if the range of intrinsic extinction within the host galaxy is narrow.Comment: 10 pages, 8 figure

Deriving physical parameters of unresolved star clusters. II. The degeneracies of age, mass, extinction, and metallicity

This paper is the second of a series that investigates the stochasticity and degeneracy problems that hinder the derivation of the age, mass, extinction, and metallicity of unresolved star clusters in external galaxies when broad-band photometry is used. While Paper I concentrated on deriving age, mass, and extinction of star clusters for one fixed metallicity, we here derive these parameters in case when metallicity is let free to vary. The results were obtained using several different filter systems ($UBVRI$, $UBVRIJHK$, GALEX+$UBVRI$), which allowed to optimally reduce the different degeneracies between the cluster physical parameters. The age, mass, and extinction of a sample of artificial star clusters were derived by comparing their broad-band integrated magnitudes with the magnitudes of a large grid of cluster models with various metallicities. A large collection of artificial clusters was studied to model the different degeneracies in the age, mass, extinction, and metallicity parameter space when stochasticity is taken into account in the cluster models. We show that, without prior knowledge on the metallicity, the optical bands ($UBVRI$) fail to allow a correct derivation of the age, mass, and extinction because of the strong degeneracies between models of different metallicities. Adding near-infrared information ($UBVRI$+$JHK$) slightly helps in improving the parameter derivation, except for the metallicity. Adding ultraviolet data (GALEX+$UBVRI$) helps significantly in deriving these parameters and allows constraining the metallicity when the photometric errors have a Gaussian distribution with standard deviations 0.05 mag for $UBVRI$ and 0.15 mag for the GALEX bands.Comment: 8 pages, 9 figure

Development of a new hazelnut sandwich ELISA based on detection of Cor a 9, a major hazelnut allergen

The emerging health problem of food-induced allergic reactions, including life-threatening anaphylaxis, presents an important challenge to the food. In the framework of the current ALLERRISK project, analytical approaches for allergen detection are evaluated and developed. Cor a 9 is a major hazelnut protein with nutrient reservoir function, and that also known as a major food allergen. Presence of Cor a 9 indicates contamination of a product with hazelnut and, consequently, potential risk of allergenicity. Crude extract of hazelnut was obtained from milled mixture of hazelnuts from 10 commercially available brands. Then the extract was concentrated and applied to gel filtration and Con A affinity chromatography columns for Cor a 9 isolation and purification. The final product was characterized by analytical gel permeation chromatography, SDS PAGE and MALDI mass spectrometry. The purified Cor a 9 was used as an antigen for the production of polyclonal antibodies in chickens according to the protocol developed in our laboratory. A part of the most active antibodies was further purified by gel permeation chromatography and characterized by SDS PAGE before further use. The prepared antibodies were applied for development of a sandwich ELISA using polyclonal antibody-enzyme adducts as a tracer. Optimization of reagent concentrations led us to achieve detection limit ~10 ng/ml. Influence of ionic strength, pH and buffer composition on analytical parameters of the developed ELISA were thoroughly studied. The developed ELISA can be successfully applied for quantitative detection of Cor a 9 in large pH (pH = 5 – 10) and ionic strength (0.05 – 1.5 M salts solution) ranges. Cross-reactivity with series of nuts, ovalbumin, whey, and wheat proteins was also investigated (Figure 2) and showed that the developed assay was very specific. Moreover, presence of several other proteins (peanut, cashew, ovalbumin, whey and wheat) at high concentrations (1 mg/ml) in the presence of Cor a 9 did not influence the calibration curve of Cor a 9. Detection of hazelnut protein in cookies with known amount of hazelnut inside initial dough showed good recovery (35-40%) and absence of significant signal in blank samples (i.e. without spiking of hazelnut)