Ripening and changes in chemical composition of seven cider apple varieties

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.