Helena Morais

Optimisation of the microwave-assisted extraction of pigments from paprika (Capsicum annuum L.) powders

The efficiency of microwave-assisted extraction (MAE) for the extraction of colour pigments from paprika (Capsicum annuum) powders was evaluated using 30 extracting solvent mixtures. The separation efficacy and selectivity of MAE was carried out using a spectral mapping technique and the relationship between the efficacy and selectivity of extraction and the physicochemical parameters of solvent mixtures was calculated by stepwise regression analysis. The calculation results were verified experimentally by the separation of pigment fractions by high-performance liquid chromatography. It was established that both the efficacy and selectivity of MAE depend significantly on the dielectric constant of the extraction solvent mixture.

Influence of storage conditions on the stability of monomeric anthocyanins studied by reversed-phase high-performance liquid chromatography

The effect of light, storage time and temperature on the decomposition rate of monomeric anthocyanin pigments extracted from skins of grape (Vitis vinifera var. Red globe) was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). The impact of various storage conditions on the pigment stability was assessed by stepwise regression analysis. RP-HPLC separated well the five anthocyanins identified and proved the presence of other unidentified pigments at lower concentrations. Stepwise regression analysis confirmed that the overall decomposition rate of monomeric anthocyanins, peonidin-3-glucoside and malvidin-3-glucoside significantly depended on the time and temperature of storage, the effect of storage time being the most important. The presence or absence of light exerted a negligible impact on the decomposition rate.

Liquid chromatographic and electrophoretic characterisation of extracellular β-glucosidase of Pleurotus ostreatus grown in organic waste

The production of beta-glucosidase by the ligninolytic fungus Pleurotus ostreatus has been studied in different culture media containing agro-industrial wastes. The enzyme is purified by anion-exchange chromatography, the molecular mass and isoelectric point of purified beta-glucosidase are measured by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing and the stability and kinetic parameters of the enzyme assessed by spectrophotometry. It has been established that the retention time, molecular mass and isoelectric point of the enzyme depend on the composition of the culture media while the activity and stability of beta-glucosidases of different origin were very similar. The combined chromatographic and electrophoretic methods have proved to be suitable techniques for the purification and characterisation of the beta-glucosidases produced by the ligninolytic fungus Pleurotus ostreatus in different culture media.

Three-dimensional principal component analysis employed for the study of the β-glucosidase production of Lentinus edodes strains

Abstract The effect of cation type and concentration and fermentation time on the β-glucosidase production of four strains of Lentinus edodes was determined. Three-dimensional principal component analysis (3D-PCA) followed by nonlinear mapping technique (NLMAP) was employed for the assessment of similarities and dissimilarities between the enzymatic activities. No linear relationship was found between the effect of cations on the enzyme production and their ion radii, concentration and charge. Enzyme production was similar between 20 and 40 days of fermentation then changed considerably. The enzyme activities of strains also showed marked differences. The results proved that 3D-PCA followed by NLMAP is a valuable tool for the evaluation of three-dimensional data matrices in biology and microbiology too.

Note. Effect of Blanching and Frozen Storage on the Stability of β-Carotene and Capsanthin in Red Pepper (Capsicum Annuum) Fruit

The effect of blanching and frozen storage on the stability of pigments β-carotene and capsanthin in three cultivars of red pepper (Capsicum annuum) fruits was elucidated by the determination of pigments in samples treated by various blanching procedures. Pigment concentration was performed after different storage times by HPLC. The dependence of the concentration of pigments on the conditions of blanching and the storage time was assessed by stepwise regression analysis, and the similarities and dissimilarities among the cultivars and decomposition rates were calculated by principal component analysis. The stability of pigments depended significantly on the conditions of blanching, the storage time and the type of cultivar, the effect of storage time was higher than that of blanching conditions. The significant differences between the decomposition rate of pigments in various cultivars emphasizes the predominant importance of the selection of cultivars with advantageous storage characteristics. Se analizó el efecto del escaldado y almacenamiento en congelación de tres variedades de pimiento rojo, escaldado mediante diferentes procesos, en la estabilidad del β-caroteno y capsatin. La determinación de los pigmentos se hizo mediante HPLC. La relación entre la concentración y las condiciones del escaldado se evaluó mediante el análisis de regresión por pasos, y las similitudes o no entre variedades y el grado de descomposición se hizo mediante el análisis de componentes principales. La estabilidad de los pigmentos dependió significativamente de las condiciones del escaldado, del tiempo de almacenamiento y del tipo de variedad, aunque el efecto del tiempo de almacenamiento fue mayor que el de las condiciones de escaldado. Las diferencias significativas entre el grado de descomposición de los pigmentos en función de las condiciones de escaldado puso de manifiesto la gran importancia de la selección de la variedad con las características más ventajosas para su almacenamiento.

Classification of chili powders by thin-layer chromatography and principal component analysis.

Silica gel, aluminium oxide, diatomaceous earth, polyamide, cyano, diol and amino plates have been tested for their capacity to separate the color pigments of six chili powders of different origin by both adsorption and reversed-phase thin-layer chromatography. The plates were evaluated at 340 and 440 nm wavelengths. Best separation of color pigments was obtained on impregnated diatomaceous earth layer using acetone-water 17:3 v/v eluent. It was found that the pigment composition of chili powders showed marked differences. Principal component analysis employed for the classification of the chili powders according to their pigment composition indicated that these differences can be used for the determination of the similarity or dissimilarity of the chili powders.

Profiling of colour pigments of chili powders of different origin by high-performance liquid chromatography

The colour pigments of five chili powders of different origins were separated and quantified by reversed-phase high-performance liquid chromatography (RP-HPLC). The similarities and dissimilarities of pigment composition of chili powders were elucidated by principal component analysis (PCA). RP-HPLC separated 50-100 pigment fractions depending on the detection wavelength and on the origin of chili powder. It was found that the pigment composition of chili powders from Malaysia and China and from India and Pakistan show marked similarities while the composition of colour pigments of chili powder from Thailand was different. It was further established that the chromatograms are similar in the first 5-35 min of development, they are highly different between 35 and 75 min and moderately different at the end of the chromatograms. It was concluded that RP-HPLC followed by PCA can be successfully used for the identification of chili powders according to the composition of their colour pigments.

Inclusion of the standard deviation of data in spectral mapping. A case study

Abstract Colour pigments of paprika powders of different origin were separated and quantitatively determined by reversed-phase high performance liquid chromatography. The standard deviations were included in the matrices of retention data and the matrices were evaluated by spectral mapping technique followed by two-dimensional nonlinear mapping. The resuls indicated that the distribution of paprika samples on the two-dimensional selectivity map is a better indicator of the origin of the samples, compared to what the potency values do, and the inclusion of the standard deviation of raw data may be employed as a useful tool to enhance the reliability of the authenticity test of paprika samples.

Use of HPLC and multivariate methods for the evaluation of the stability of colour pigments of paprika (Capsicum annuum) powder

The effect of storage conditions and the addition of seeds on the stability of the colour pigments of paprika (Capsicum annuum) was studied. Pigments were separated by reversed-phase high performance liquid chromatography, and the influence of the storage conditions on the rate and selectivity of the decomposition was assessed by spectral mapping technique followed by two-dimensional nonlinear mapping and stepwise regression analysis. It was established that the length of storage exerts the highest impact on the decomposition rate whereas the selectivity of decomposition depends on both the concentration of the added seeds and on the length of storage. The lipophilicity of pigments did not influence their decomposition rate.

Effects of fluorescent light and vacuum packaging on the rate of decomposition of pigments in paprika (Capsicum annuum) powder determined by reversed-phase high-performance liquid chromatography

The effect of storage time, the presence of light and oxygen on the decomposition rate of carotenoid pigments in paprika (Capsicum annuum) powders was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). The similarities and dissimilarities of pigment composition of samples under various storage conditions was elucidated by principal component analysis (PCA) and stepwise regression analysis (SRA). Calculations proved that the overall decomposition rate of pigment sections equally depended on the storage time and on the presence of light and oxygen, the effect of storage time being the most decisive factor while the impact of oxygen was the lowest. The selectivity of decomposition also depended on the storage time and on the presence of oxygen the influence of storage time being the most important. RP-HPLC followed by PCA and SRA can be successfully used for the study of the impact of environmental conditions on the decomposition of carotenoid pigments of paprika powders.