The low field region (5.8-9.0 ppm) corresponding to aromatic protons and the region 1.8-3.0 ppm of the (1)H NMR spectra were used for characterization and chemometric differentiation of 52 apple juices obtained from six cider apple varieties. The data set consisted of 14 integrated areas corresponding to resonances from acids and phenolic compounds. Multivariate procedures based on hierarchical cluster and discriminant analysis were performed on selected signals of the spectra to determine whether it was possible to distinguish the different juices. Cluster analysis was able to satisfactorily classify the six apple varieties. Discriminant analysis, by means of stepwise procedure for variables selection and leave-one-out for cross-validation, was applied to 40 samples from the year 2001, obtaining recognition and prediction abilities of 100%. The most discriminant variables corresponded to poliphenols, (-)-epicatechin, phloridzin-phloretin, and p-coumaric, chlorogenic, and malic acids. The classification model was applied to 12 samples from apples harvested in the years 2002 and 2003, and the prediction ability was 91.7%.

Changes in composition of seven Basque cider apples ( Malus x domestica Borkh.) varieties were studied for 5 weeks before harvesting, while the apples were still on the tree. The evolution of 21 parameters was measured. Special emphasis was made on the sugars, acidity and total phenolic compounds, responsible, respectively, for the sweet, acid and bitter taste of apples and their juices. The whole composition data throughout the ripening process are given. Correlation analysis was used to verify the usefulness of polyphenol index (absorbance at 280nm) for estimating the total phenolic content in apple juices. A high correlation was found between this index and the total phenolic content, either for each apple variety or for all the varieties together, demonstrating the usefulness of polyphenol index to carry out the estimation in these samples. Cluster analysis was used to find patterns of clustering between the apple varieties studied. The apple samples were classified into seven groups, coincident with the seven varieties studied. This proved that the ripening state did not affect this classification, in spite of the changes produced in the composition of apples. Principal component analysis was used to summarise the information of the data matrix in a more reduced way. Acidity (PC1) and phenolic compounds (PC2) were the most relevant parameters for discrimination of apple varieties.

The changes in the magnetic properties ͑coercive field and saturation magnetostriction͒ of Ni 5 Fe 68.5 Cu 1 Nb 3 Si 13.5 B 9 amorphous alloy after thermal treatment are reported. In order to develop a nanocrystalline structure, the thermal annealing was carried out by Joule heating currents of 1.7 and 1.8 A during different annealing times. Additionally, a microstructural characterization of the treated samples was performed by x-ray diffraction, determining the partial volume of the two, crystalline grains and residual amorphous matrix, existing phases. They seem to be correlated to the softening of the nanocrystallized samples in comparison to the as-cast one.

No abstract

No abstract