Use of principal component analysis to evaluate the physical properties of Mahon cheese

Abstract

The texture, colour and water activity of the seven existing types of Mahon cheese, manufactured under the Mahon cheese Appellation of Origin, were studied using eight physical variables. Four of the types are industrially manufactured [fresh (less than 10 days of ripening), half-ripened (2-5 months of ripening), ripened (5-10 months of ripening) and old-ripened (more than 10 months of ripening)] and three are traditionally manufactured (half-ripened, ripened and old-ripened). ANOVA, Tukey's multiple range test and principal component analysis (PCA) were used. Mahon cheeses from different ripening periods exhibited significant differences in water activity and yellowness values (P<0.001). PCA reduced the eight physical variables to two independent components, which accounted for 84.4% of the total variance. The first principal component (PC1) separated cheeses characterised by high water activity, high springiness values and slight yellowness from those with high hardness and puncture force; PC1 therefore distinguished among samples from different ripening periods. Cohesiveness, chewiness and gumminess were highly correlated in the second principal component, which could be interpreted as an index of cohesiveness.