Principal Components Analysis (PCA) and Hierarchical
Classification Analysis (HCA)
The score graph obtained from the PCA analysis of olive oils obtained
from the provinces in 2017 according to the variety is shown in Figure 3
(a). According to the PC1 results, the orchards were divided into two
main groups, one group where the Gemlik variety was harvested, and the
other group where the Nizip Yağlık and Kilis Yağlık varieties were
harvested. According to the results of the PC2, the orchards were
divided into two main groups, one group where the Ayvalık variety was
harvested, and the other group where the Memecik variety was harvested.
The border between the two groups is not as wide as the difference
between Gemlik and Kilis Yağlık-Nizip Yağlık varieties. The probable
reason for this may be that the Gemlik cultivar samples come from a
relatively wider range of geographical regions. In 2017, the cultivars
were successfully clustered into subgroups on the basis of cultivars
according to the orchard from which they were harvested. The loading
graph obtained from the PCA analysis is shown in Figure 3 (b). It is
seen that the margoleic acid and palmitoleic acid contents are quite
determinant especially in the classification and characterization of the
Gemlik variety samples. It is seen that one of the most prominent
variables in the characterization of Kilis Yağlık and Nizip Yağlık
samples were stearic acid. It is seen that the gadoleic acid variable
comes to the fore in the characterization of Ayvalık and Memecik
cultivars (Figure 3 (b)).
FIGURE 3 (a) Score graph obtained from PCA analysis of olive
oils obtained from regions, (b) PCA loading graph of olive oils obtained
from the regions in 2017 according to varieties
According to the PC1 results in 2018 (Figure 4 (a)), the orchards were
divided into two main groups one group where the Ayvalık variety was
harvested, and the other group where the Memecik variety was harvested.
According to the results of the PC2, the orchards were divided into two
main groups one group where the Gemlik variety was harvested, and the
other group where the Nizip Yağlık–Kilis Yağlık variety was harvested.
Varieties were successfully clustered into subgroups on the basis of
variety in 2018 according to the orchards from which they were
harvested. It is seen in Figure 4 (b) that margoleic acid, oleic acid
and palmitoleic acid contents are quite decisive in the classification
and characterization of Gemlik samples. It is seen that one of the most
prominent variables in the characterization of Kilis Yağlık and Nizip
Yağlık samples is arachidic acid. The linoleic acid variant also comes
to the fore in the characterization of the Memecik cultivars.
FIGURE 4 (a) Score graph obtained from PCA analysis of olive
oils obtained from regions, (b) PCA loading graph of olive oils obtained
from regions in 2018 according to varieties
In 2019, the orchards where the Memecik variety was harvested were
divided into a group according to the PC1 results (Figure 5 (a)).
According to the results of the PC2, the orchards where the Nizip Yağlık
variety was harvested are separated as a group. In 2019, the cultivars
were successfully clustered into subgroups only as Memecik and Nizip
Yağlık, according to the orchards where they were harvested. When the
loading graph was examined closely, it was determined that the linoleic
acid, linolenic acid and gadoleic acid contents were quite determinative
in the classification and characterization of the Memecik variety
samples (Figure 5 (b)). It was determined that one of the most
significant variables in the characterization of Nizip Yağlık samples
was arachidic acid.
FIGURE 5 (a) Score graph obtained from PCA analysis of olive
oils obtained from regions, (b) PCA loading graph of olive oils obtained
from regions in 2019 according to varieties
In 2020, the orchards where Kilis Yaglik and Nizip Yaglik varieties were
harvested were divided into a group (Figure 6 (a)). According to the
results of the PC2, the orchards where the Memecik variety was harvested
were separated as a group. In 2020, the cultivars were successfully
clustered into subgroups only as Memecik and Kilis Yağlık-Nizip Yağlık
according to the orchards where they were harvested. It has been
determined that linoleic acid contents may be determinant in the
classification and characterization of the Memecik samples (Figure 6
(b)). It is seen that one of the most prominent variables in the
characterization of Nizip Yağlık samples is arachidic acid.
FIGURE 6 (a) Score graph obtained from the PCA analysis of
olive oils obtained from the regions, (b) PCA loading graph of olive
oils obtained from regions in 2020 according to varieties