Javier Tabera

Liquid chromatographic-mass spectrometric analysis of supercritical-fluid extracts of rosemary plants.

A two-step supercritical fluid extraction process of rosemary leaves, on a pilot plant scale, is proposed to divide the oleoresin into two fractions with different antioxidant activities and essential oil composition. Rosemary leaves were extracted by using different conditions of pressure and temperature as well as different conditions for fractionation of the extracts. Conditions can be tuned to selectively extract one antioxidant fraction with almost no residual aroma. In the present investigation, the antioxidant fraction was exhaustively studied in terms of antioxidant activity measurements as well as of chemical composition. An LC-MS method was adapted to perform the analysis and identification of the compounds responsible for the antioxidant activity of the extracts. Different extraction and fractionation conditions were studied in order to correlate the process conditions with the antioxidant activities obtained.

Analysis of volatile fruit components by headspace solid-phase microextraction

A method based on headspace solid-phase microextraction (HS-SPME) has been developed for the analysis of volatile compounds in fruits. Conditions of sampling have been tuned. Repeatability and recoveries obtained with this method have been determined by using a mixture of typical components of fruit aroma. Several fruits, such as raspberries, strawberries, blackberries, banana and mango, have been analysed by the proposed method. The patterns obtained include compounds typically found in fresh fruits and compounds formed during processing or storage. The results showed the use of the technique for fruit characterization and its potential as a routine method for analyzing changes in key flavour compounds during different fruit processing regimes.

Differences among Spanish and Latin-American banana cultivars: Morphological, chemical and sensory characteristics

Physical (weight, size, shape, texture and colour), physicochemical (pH, titratable acidity, soluble solids, moisture content, total solids), chemical (soluble sugars, vitamin C, starch, pectic substances, volatile compounds) and biochemical (polyphenol oxidase and peroxidase activities, soluble proteins) characteristics and sensory attributes (appearance, flavour, odour, colour, firmness, acceptability) of banana (Musa cavendishii L.) fruits were studied in order to assess possible differences between nutritional properties and consumer acceptability of the local (Canarian) cultivars Enana and Gran Enana and the Latin-American (Colombian) Enana cultivar. Significant differences (P ≤ 0·05) were found between size and length of fruit, and between other objective measurements (lightness, yellowness, acidity, moisture content, starch, peroxidase and polyphenol oxidase activities, soluble sugars—sucrose, fructose, glucose). Also there were significant differences in vitamin C and protein content which established the higher nutritional value of the Spanish banana cultivars. The main compositional differences between the banana cultivars in terms of flavour were quantified. Purge and trap (head-space) analysis of the Spanish Enana cultivar showed it was the richest in the characteristic banana volatile aroma compounds. Sensory descriptive analysis discriminated between banana cultivars in terms of flesh colour and flesh sweetness; although panellists liked all cultivars, they preferred the Spanish Enana fruits (overall acceptability test).

Preconcentration of volatile components of foods: optimization of the steam distillation-solvent extraction at normal pressure

Abstract Optimization of the experimental conditions affecting the simultaneous steam distillation-solvent extraction of volatile components of foods was carried out by using the modified sequential simplex method. For this purpose, a new micro steam distillation-extraction device was constructed. The apparatus includes an enlarged surface condenser which contributes to preventing eventual losses of high-volatility components. Determination in the μg/l range of compounds having different polarities and volatilities are accomplished with high recoveries. The construction of the apparatus is such that the use of extraction solvents having densities either higher or lower than that of the solvent sample is feasible with only one configuration.

Effect of natural fermentation on carbohydrates, riboflavin and trypsin inhibitor activity of lentils.

ZusammenfassungEs wurde die Linsenfermentation durch natürlich vorkommende Mikroorganismen während 4 Tage durchgeführt. Die Temperatur wurde bei 30°C gehalten. Durch die Vergärung fällt der pH-Wert auf 3,8. α-Galaktoside und Saccharose wurden in den Linsen nicht nachgewiesen, jedoch eine signifikante Zunahme des Fructosegehaltes. Es zeigte sich, daß in den Linsen die neutrale Detergent-Faser, der Cellulose- und Hemicellulosegehalt und die Trypsininhibitor-Aktivität abnimmt, aber der Lignin- und Riboflavingehalt zunimmt.AbstractLentils were subjected to natural fermentation for 4 days at 30°C. The pH value fell to 3.8 during the process. α-Galactosides and sucrose were not detected in fermented lentils but a significant increase in the fructose content was observed. In fermented lentils the neutral detergent fibre, cellulose and hemicellulose contents decreased and the lignin content increased. After fermentation the riboflavin content was higher and the trypsin inhibitor activity decreased.

Natural fermentation of lentils. Influence of time, concentration and temperature on protein content, trypsin inhibitor activity and phenolic compound content.

Lentil (Lens culinaris var. vulgaris) flour was naturally fermented for 4 days at different temperatures (28°C, 35°C and 42°C) and concentrations (79 g/1, 150 g/1 and 221 g/1). Samples were analysed to establish the changes of total protein content and in vitro protein digestibility, trypsin inhibitor activity (TIA) and phenolic compound content during natural fermentation of lentils. The preparation of lentil flour suspensions to be fermented caused a slight increase in total protein and in vitro protein digestibility content, a decrease of TIA and a sharp decrease the tannin/catechin ratio. During the whole fermentation procedure, the minimum initial lentil concentration and temperature used (79 g/1, 28°C) achieved the maximum protein content and the lowest tannin/catechin ratio. The TIA was more affected by temperature than by concentration, and a 62.5% reduction was observed at 42°C and 79 g/1.

Variables affecting the introduction of large sample volumes in capillary gas chromatography using a programmed-temperature vaporizer

Abstract The dependence of the programmed-temperature vaporizer (PTV) solvent split sampling technique on eight experimental variables affecting the introductio

Optimization of countercurrent supercritical fluid extraction conditions for spirits fractionation

Abstract Optimization of the countercurrent supercritical fluid extraction (CC-SFE) conditions to obtain distilled alcoholic drinks extracts with low alcoholic content is presented. The optimization procedure is based on the use of an experimental design and the subsequent statistical study of the data obtained. Experiments have been performed with brandy, using a countercurrent supercritical fluid extraction (CC-SFE) system on a pilot-plant scale. The beverage is brought directly into contact with the carbon dioxide current in a packed column, and the extracts are recovered in two different fractionation cells, where depressurization occurs. The main variables that influence countercurrent extraction efficiency have been studied, such as sample flow rate, solvent flow rate (that is solvent-to-feed ratio) and level of sample introduction into the extraction column. Statistical data analysis indicates the variables that clearly influence the process and also the most convenient parameter values from which to obtain a high-value concentrated extract with a rich brandy aroma and low ethanol content.

Isolation of brandy aroma by countercurrent supercritical fluid extraction

Optimization of the countercurrent supercritical fluid extraction (CC-SFE) conditions to obtain high quality brandy aroma extracts is presented. The main variables that influence CC extraction selectivity and efficiency have been studied, such as extraction pressure and temperature and sample flow rate (related to the solvent-to-feed ratio). A rotatable central composite experimental design is used to optimize the combination of these experimental. Experiments have been performed with brandy using a CC-SFE system at pilot plant scale. The beverage is put directly in contact with the carbon dioxide in a packed column and the extracts are recovered in two different fractionation cells, where depressurization occurs. For each experiment, two extracted fractions and a raffinate are obtained and its aroma characterized by gas chromatography. A statistical study of the data obtained is performed including analysis of variance (ANOVA), fitting of a regression model and response surface study. The obtained results allow to know the variables that clearly influence the process and also show the interest of CC-SFE as an useful technique to obtain high-value concentrated brandy aroma extracts.

Separation of carotenoids by subcritical fluid chromatography with coated, packed capillary columns and neat carbon dioxide

Abstract Different packed capillary columns were evaluated for carotenoid separation by subcritical fluid chromatography with neat CO2. Packed capillary columns studied involved the use of silica particles deactivated with different methods and particles coated with stationary phases commonly used in gas chromatography, such as SE-54 (95% methyl-, 5% phenylsilicone) and OV-17 (50% methyl-, 50% phenylsilicone). In order to select the appropriate chromatographic conditions to elute carotenoids, a theoretical study of the solubility of β-carotene was performed. Separation of lycopene and β-carotene was obtained with neat CO2 working at pressures around 300 atm and at a temperature of 10°C (1 atm=101 325 Pa). Evaluation of the columns used in the present study in terms of efficiency and activity was also performed.