Sagrario Beltrán

Identification of anthocyanin derivatives in grape skin extracts and red wines by liquid chromatography with diode array and mass spectrometric detection

Abstract The different options MS detection are investigated in order to achieve the best conditions for detection and identification of anthocyanins by LC–MS. A method for separation of these compounds that enables the main molecules in wines to be identified by direct analysis, without any previous preparation, is proposed. The anthocyanin composition of different red grape skin extracts and commercial monovarietal wines were determined by this method. Some recently described anthocyanin derivatives that are supposed to be formed during wine maturation were also investigated. Results showed that some of these derivatives are present in grape and young wine. The combination of diode array detection and MS analysis has been demonstrated to be essential for identification of anthocyanin derivatives.

Various applications of liquid chromatography–mass spectrometry to the analysis of phenolic compounds

Different options of liquid chromatography-mass spectrometry were used to establish the most suitable ion source and conditions to analyse or detect some low-molecular mass phenols, flavan-3-ols, and apply such conditions to a complex sample (wine). Data presented in this work confirm the great utility of atmospheric pressure-ionisation electrospray mass spectrometry coupled to HPLC for analysis of phenolic compounds, under negative mode in the case of low-molecular mass phenols, and under both positive and negative modes in flavan-3-ol compounds. A fragmentor voltage of 60 V could be the most suitable for analysing the compounds under study.

Aroma composition of wine studied by different extraction methods

Abstract Several isolation and concentration methods have been developed for the analysis of volatile components in wine. However, it is generally admitted that none of them fulfill all the requirements for the isolation of aroma compounds and that it is necessary to combine different extraction methods to obtain the complete volatile fraction. Three extraction methods have been studied: liquid–liquid extraction, static headspace and a new method developed in our laboratory, which has the same principle as the dynamic headspace technique. The volatiles were swept along with a carrier gas and later condensed in a cold trap. The advantages and disadvantages of the three methods regarding sample preparation, component losses and artifact formation, have been evaluated. Also, the sensitivity and reproducibility have been compared. With the liquid–liquid extraction method used, a new compound has been described for the first time in wine. This compound is 5,6,7,7a-tetrahydro-4,4,7a-trimethylbenzofuran-2(4H)-one. Liquid–liquid extraction and static headspace show good reproducibility; although static headspace is useful for the analysis of highly volatile compounds, it is not able to detect trace compounds due to its lack of sensitivity. The new method allows to obtain an extract, free of artifacts and foreign substances that were not in the original wine. As no solvent is used, the extracts may be tasted and sensorially analyzed.

Solubility of some phenolic compounds contained in grape seeds, in supercritical carbon dioxide

The solubility of some natural, low molecular weight phenolic compounds, 3,4-dihydroxy benzoic acid (protocatechuic acid), methyl 3,4,5-trihydroxybenzoate (gallic acid methyl ester or methyl gallate), and 3,4-dihydroxy benzaldehyde (protocatechualdehyde), in supercritical carbon dioxide (SC-CO2) has been determined at pressures from 10 to 50 MPa and temperatures from 313 to 333 K. These phenolic compounds are contained in grape seeds and other natural substrates. The data presented in this work are valuable to know the possibility of separation from their natural matrices by supercritical extraction with carbon dioxide. Data modeling has been carried out by using the Peng–Robinson equation of state (PR-EOS) to describe the behavior of the supercritical fluid (SCF) phase. Two semiempirical density dependent correlations, specifically, the Chrastil model, and a model that assumes a linear correlation between the enhancement factor and the density of the solvent, have also been used for data correlation.

Swelling equilibria for ionized temperature‐sensitive gels in water and in aqueous salt solutions

Swelling equilibrium data in water and in aqueous NaCl solutions are presented for thermally sensitive N‐isopropylacrylamide (NIPA) hydrogels containing 0–4 mol % quaternized amine (positively ionizable) comonomer. We report the effect of gel charge and solution ionic strength on the temperature‐induced collapse of NIPA gels. Experimental swelling equilibria are compared with predictions based on a recently proposed oriented‐quasichemical model. This model has been shown previously to describe lower critical solution behavior in uncharged aqueous polymer solutions and gels (i.e., aqueous NIPA gel). We apply the model here to ionized NIPA gel. Semiquantative predictions are obtained for the effects of gel charge and solution ionic strength on temperature‐dependent swelling behavior.

Anaerobic pre-treatment of slaughterhouse wastewater using fixed-film reactors

Abstract The aim of this work was to study the performance of anaerobic fixed-film reactors with non-random support, for poultry slaughterhouse wastewater pre-treatment, including the influence of operating conditions. The work was carried out with two lab-scale reactors, one upflow and the other downflow, both equipped with vertical corrugated PVC tubes as support and a recirculation circuit. Both reactors were operated at 35°C. COD removal efficiencies ranging from 85% to 95% were achieved for organic loading rates of 8 kg COD m −3 d −1 , while the highest organic loading rates (35 kg COD m −3 d −1 ) led to efficiencies of 55–75%. The reactors did not show destabilization after 12 h shock loads of 50 kg COD m −3 d −1 . Reactor stability was easily achieved under intermittent operation, with weekend breaks, after which the reactors rapidly returned to their optimal performance. The influences of the hydraulic retention time, temperature, the recirculation ratio and flow direction were also studied.

Solubility of three hydroxycinnamic acids in supercritical carbon dioxide

The solubility of three trans-hydroxycinnamic acids, 4-hydroxycinnamic acid (p-coumaric acid), 3,4-dihydroxycinnamic acid (caffeic acid), and 4-hydroxy-3-methoxycinnamic acid (ferulic acid), in supercritical carbon dioxide (SC-CO2) has been determined at different pressures up to 50 MPa and temperatures from 313 to 333 K. These hydroxycinnamic acids are phenolic compounds contained in grape seeds and other natural substrates, and the data presented in this work are valuable to know the possibility of their separation from such natural matrices by extraction with SC-CO2. Experimental data have been modeled by using the Peng–Robinson equation of state (PR-EOS) to determine the fugacities of the fluid phase. Two semiempirical density dependent correlations have also been used for data correlation, specifically, the Chrastil model, and a model that assumes a linear correlation between the enhancement factor and the density of the solvent.

Membrane sequences for fractionation of polyphenolic extracts from defatted milled grape seeds

Membrane technologies are presented as alternative techniques to purify and fractionate extracts from winery wastes with the aim of obtaining proanthocyanic fractions with different degrees of polymerization. These fractions, with the appropriate purity, have a great interest nutritionally and pharmacologically. To achieve different streams enriched in proanthocyanidins (PAs) with certain degree of condensation, several cross-flow filtration sequences using several polymeric membranes at different stages in the sequences were carried out. At the same time, several transmembrane pressures, concentrations and filtration designs (with or without diafiltration) were tested in tubular modules. A final sequence with four different membranes at the pilot-plant scale was achieved, which permitted us to obtain different fractions according to the molecular weight, some of them very pure in oligomeric PAs and, therefore, very interesting for the biotechnological industry. The raw material used in all cases was a hydroalcoholic extract from defatted milled grape seeds. Although no high yield was achieved in the whole process, the low value of this raw material (considered a waste in the winery industry) and the purity of the fractions obtained decrease the significance of the global yield.

Formulation and characterisation of wheat bran oil-in-water nanoemulsions

Wheat bran oil (WBO) has been reported to have an important content of bioactive compounds, such as tocopherols, alkylresorcinols, steryl ferulates and other phenolic compounds; however, its poor solubility in water systems restricts its applications in the food industry. This study is focussed on the formulation of oil-in-water (O/W) nanoemulsions of WBO in order to improve the bioaccessibility of its active compounds. The influences of oil concentration, surfactant type and concentration, and emulsification method, on the droplet size and stability of the nanoemulsions were investigated. Response surface methodology was used to optimise the conditions for preparing stable nanoemulsions with the minimum droplet size. The optimal nanoemulsion was obtained when 1% of WBO and 7.3% of a surfactant mixture of Span 80 (37.4%) and Tween 80 (62.6%) were emulsified in water by high intensity ultrasonication for 50s after pre-emulsification with a high speed blender during 5 min. The optimal nanoemulsion showed good stability over time and antioxidant and tyrosinase inhibitory activities, which make it suitable for use in food applications.

Production and concentration of monoacylglycerols rich in omega-3 polyunsaturated fatty acids by enzymatic glycerolysis and molecular distillation

Production of monoacylglycerols (MAGs) rich in ω-3 polyunsaturated fatty acids (n-3 PUFAs) was conducted through short path distillation (SPD) of an acylglycerol mixture (containing 67% MAGs) produced by enzymatic glycerolysis of sardine oil with glycerol. A stepwise SPD process in a UIC KDL 5 system (vacuum 10(-3)mbar, feeding flow 1.0 mL/min) was proceeded: the first distillation performed at evaporator temperature (TE) of 110 °C to remove glycerol completely and most of FFAs; and the second distillation at optimized TE 155 °C; resulting in a stream distillate with 91% purity and 94% overall recovery of MAGs. This work also demonstrated that SPD is able to concentrate n-3 PUFAs in MAG form by distilling at proper TE e.g. 125 °C, where n-3 PUFAs are concentrated in the residues. Moreover, this work mapped out a complete processing diagram for scalable production of n-3 PUFAs enriched MAGs as potential food emulsifier and ingredient.