Esperanza Fernández Gómez

Aromatic composition of the Vitis vinifera grape Albariño

The Vitis vinifera Albarino is a considerably acid white Galician variety, with an important aromatic potential. The composition of the grape at the harvest date during four consecutive years is reflected in this paper. The normal parameters of total acidity, pH, and sugar and malic acid contents, were determined according to the official methods of the OIV. Aromatic compounds extracted from the grape sample using C18 cartridges were identified and quantified by gas chromatography/mass spectrometry. The results obtained demonstrate a high content of bound form aromatic compounds and that, of the responsible compounds for the varietal aroma, linalool, geraniol, benzyl alcohol and 2-phenylethanol predominate. This supports the observation of the floral character of the variety.

Comparison of slurry sampling and microwave-assisted digestion for calcium, magnesium, iron, copper and zinc determination in fish tissue samples by flame atomic absorption spectrometry.

The development of a slurry sampling method for the determination of calcium, copper, iron, magnesium and zinc in fish tissue samples by flame atomic absorption spectrometry is described. In comparison with microwave-assisted digestion, the proposed method is simple, requires short time and eliminates total sample dissolution before analysis. Suspension medium was optimized for each analyte to obtain quantitative recoveries from fish tissue samples without matrix interferences. Nevertheless, iron recoveries higher than 46% were not found. Treatment of samples slurried in nitric acid by microwave irradiation for 15-30s at 75-285W permitted to achieve efficient recoveries for calcium, iron, magnesium and zinc. Further improvement in the matrix effects for iron determination was accomplished by the use of an additional step of short microwave-assisted suspension treatment. However, standard addition method was required for calcium and copper determination, being necessary hydrochloric acid as suspension medium for the last one. Although copper could not be determined in the certified reference material using microwave-assisted digestion, the accuracy of the slurry sampling method was verified for all the investigated analytes. Detection limits were 22.8+/-8.0, 0.884+/-0.092, 5.07+/-0.76, 35.5+/-0.7 and 1.17+/-0.04mugg(-1) for calcium, copper, iron, magnesium and zinc, respectively. The standard deviations obtained using slurry sampling method and microwave-assisted digestion were not significantly different, and the mean relative standard deviation of the over-all method (n=3) of the slurry sampling method for different concentration levels was below 12%.

A Fractional Factorial Design Applied to the Optimization of Microwave- and Ultrasound-Assisted Acid Leaching Methods for Heavy Metals Determination in Sludges by Flame Atomic Absorption Spectrometry

Microwave-assisted extraction, ultrasound-assisted extraction and microwave-assisted digestion were compared for the determination of chromium, copper, lead and zinc in sludge samples by Flame atomic absorption spectrometry (FAAS) in terms of accuracy, precision, sample throughput and manipulation risk. The complete destruction of the matrix required the use of high temperature, elevated pressure and concentrated acids and the introduction of several time consuming steps, such as a cooling step of the digester and an evaporation step of the concentrated acids. The accelerated extraction procedures using dilute acids as extractants were optimised in order to reduce the treatment time and avoid the risks associated to the use of pressurised digesters. The capabilities of the Plackett–Burman saturated factorial design were explored to study the effect of various parameters on the extraction efficiency. The applicability of both extraction methods for sludge samples analysis of different origin was shown using principal component analysis and cluster analysis.

Incidence of the Winemaking Technique on Metal Content and Phenolic Composition of Red Wines

The influence of different winemaking techniques usually used to elaborate red wines (Ganimede, prefermentative maceration, pectolytic enzymes and tannins addition, oak chips addition, delestage, and conventional procedure) on the metal content was evaluated. Linear discriminant analysis was also used to characterize the respective wines based on the metal content. By using iron, manganese, and calcium as chemical descriptors, the six winemaking techniques were perfectly discriminated. As the phenolic composition is an important quality factor in red wines, a correlation study between phenolic compounds and metals was also performed. A good correlation has been found for iron, calcium, and potassium with total polyphenols, tannins, and flavanols reactive. Iron, zinc, calcium, and potassium showed a significant correlation with anthocyanin compounds. Furthermore, higher concentrations of iron and calcium, but lesser ones of potassium, permitted to obtain red wines with a greater chromatic intensity.The influence of different winemaking techniques usually used to elaborate red wines (Ganimede, prefermentative maceration, pectolytic enzymes and tannins addition, oak chips addition, delestage, and conventional procedure) on the metal content was evaluated. Linear discriminant analysis was also used to characterize the respective wines based on the metal content. By using iron, manganese, and calcium as chemical descriptors, the six winemaking techniques were perfectly discriminated. As the phenolic composition is an important quality factor in red wines, a correlation study between phenolic compounds and metals was also performed. A good correlation has been found for iron, calcium, and potassium with total polyphenols, tannins, and flavanols reactive. Iron, zinc, calcium, and potassium showed a significant correlation with anthocyanin compounds. Furthermore, higher concentrations of iron and calcium, but lesser ones of potassium, permitted to obtain red wines with a greater chromatic intensity.