Principal component analysis allowed us to visualize and summarize all the differences highlighted by the ANOVA results. The
eigenvalues of the correlation matrix showed that the first three
Principal Components (PCs) explained 83% of the total variance. The
first two PCs explained 41.09% and 29.67%, respectively. The PCA
biplot (Fig. 5) showed that total phenols and antioxidant capacity
were highly correlated reciprocally and with the same positive direction as PC1, being located to the right in the plot. They were
responsible for most of the variance captured by PC1. Sodium
content and, especially, h
were located to the left in the plot,
inversely correlated with PC1 and with total phenols and antioxidant capacity. On the same side, but with less influence on the PC1
spanning variation, wereL
*
andb
*
(Fig. 5). Examining the product
distribution (Fig. 5), we find raw purple carrot and purple mild jam located on the right, corresponding to total phenols and antioxidant
capacity, while raw yellow carrot and yellow common jam were
located on the left. These results, confirming the ANOVA results,
highlighted that purple carrots are rich in antioxidants and phenols
and that these traits are not greatly modified by the mild jam
processing method.
PC2 was mainly influenced by calcium, potassium and magnesium content, and L
*
, a
*
and b
*
color parameters were located in the
upper part of the plot, while in the lower part no features were
found to be strictly correlated to PC2 (Fig. 5). Raw commercial and
orange carrots were associated with L
*
and b
*
parameters, while
almost all the common jams were related to the negative direction
of PC2, mainly due to the inverse relationship with their potassium
content.