Principal component analysis as tool of characterization of quince (Cydonia oblonga Miller) jam

Fifty-one quince jams from several different brands, commercialised in three consecutive years, traditionally prepared and industrially manufactured, were studied. Principal component analysis (PCA) was performed, in order to assess the correlations between the different components of quince jam phenolics, organic acids and free amino acids. Phenolics determination was the most interesting. The differences between phenolic profiles of traditional and industrial quince jams were emphasised during PCA. Two main PC characterise the quince jam phenolic composition (54.4% of all variance): PC1 (37.4%) and PC2 (17.0%). The PC1 describes the differences between the contents of 3-O- and 5-O-caffeoylquinic acids and all flavonoids and the PC2 relates the contents of 4-O- and 5-O-caffeoylquinic acids against 3-O-caffeoylquinic and 3,5-dicaffeoylquinic acids. The results indicate that many industrial manufacturers usually use unpeeled fruits in the preparation of the jams. The PCA of phenolic compounds enabled clear discrimination between quince jams prepared with peeled and unpeeled fruits.