# Evaluation of Hazelnut Cake Flour for Use as a Milk Powder Replacer in Ice Cream
## 3 Results and Discussion
### Principal Component Analysis  
To effectively illustrate the relationships among ice cream samples that incorporate partial and complete substitutions of SMP with HPCF, as well as their respective properties, a Principal Component Analysis (PCA) was conducted utilizing the data provided in Tables 2-5 and Figures 3 and 5. The connections between the physicochemical and rheological parameters of the ice cream mixtures, along with the physical and sensory attributes of the final product, are depicted in Figure 6. PCA accounted for 94.53% of the overall variance in the examined ice cream data. The first component (F1) represented 75.36% of the total variability, while the second component (F2) contributed 19.17%. The formulations of HPCF ice cream were organized into four distinct, partially overlapping groups as seen in Figure 6: control; HN1 and HN2; HN3; and HN4, based on these two components. F1 distinctly categorized ice cream samples according to their principal chemical composition, followed by physical attributes such as acidity, water activity, overrun, fat destabilization index, as well as rheological characteristics, texture, and melting properties. Moreover, F1 also distinguished the samples based on the most of the examined colour parameters, with the exception of the \(b^{*}\) value and chroma. It also factored in the sensory ratings for mouthfeel. This suggests that mouthfeel, as a textural attribute, is more important than other sensory aspects, like flavour and aroma, in differentiating HPCF ice cream samples and is directly related to formulation changes. The first component also relates to supplementary variables, %SMP and %HPCF, indicating that changes in these ingredients significantly influence all previously mentioned parameters. The content of HPCF in the ice cream formulations demonstrated (Figure 6b) a significant positive correlation with fat content, acidity, water activity, viscosity, and thixotropy of the ice cream mixture. It also correlated positively with hardness, gumminess, cohesiveness, first drop time, total melting time, and various colour parameters, including the intensity of green-red colouration, browning index, and total colour differences. These attributes were particularly associated with the ice cream samples HN3 and HN4, which are situated on the right side of the PCA plot. In contrast, the HPCF content showed a negative correlation with the levels of protein, carbohydrates, total solids, and milk solids not-fat (MSNF), as well as the pH of the mixture. Additionally, it was negatively associated with overrun, FDI value, and sensory evaluations for mouthfee, along with melting rate, adhesiveness, and instrumental assessments of lightness, hue, and whiteness index. These factors were especially related to the control ice cream samples, as well as HN1 and HN2, placed on the left side of the plot. Conversely, F2 classified ice cream according to sensory evaluation. As a result, samples with a partial replacement of SMP by HPCF (HN1, HN2, and HN3), which exhibited a greater preference in terms of taste, aftertaste, appearance, and aroma were located in the lower section of the PCA plot. In contrast, the control sample (C) and the variant where SMP was fully substituted with HPCF (HN4) were positioned in the upper region of the graph, receiving the lowest ratings among the evaluated ice creams. Scoopability as an attribute did not serve to differentiate the ice creams based on the first two PCA components. This parameter is important for consumer experience, and although not illustrated in detail within the biplot analysis, the third principal component (F3) specifically addresses scoopability sensory scores. However, it appears to be less influential than physicochemical properties or general sensory perceptions represented by F1 and F2 components in distinguishing HPCF-enriched ice creams. Figure 6: Principal component analysis (PCA): (**a**) bootstrap ellipses and (**b**) biplot graph for ice cream with hazelnut press cake flour.