Opposite shapes appearing on the PCA biplots are significantly differentiated by the Duncan test. The Wing and the Sail were significantly more intense in cocoa than the Trapezoid, Round and Rectangle shapes (Fig. 5a). Despite caramel flavour being perceived at very low intensities (mean scores < 1), results showed that the Trapezoid shape was significantly more intense than the Rectangle,Ellipsoid and Oval shapes (graph not shown). The Sail shape
aftertaste was significantly more intense than for Triangle, Oval and Catstongue 1 shapes (Fig. 5b). As deformation, melting, and smooth and powdery were strongly correlated, the focus from here on would only be on melting and smooth attributes. The shape perceived to melt the most was the Round. It was significantly more melting than Ellipsoid, Sail, Wing, Trapezoid, Catstongue 2 and triangle shapes. The shapes perceived to melt the least were
Ellipsoid, Sail and Wing (Fig. 5c). The Rectangle shape was perceived significantly smoother than the Ellipsoid, the Sail, the
Catstongue 1 and the Wing shapes. The Sail and the Ellipsoid were the least smooth samples (Fig. 5d).
From these results, the most promising shapes in terms of flavour (high cocoa, high caramel notes and high aftertaste) were the Wing and the Sail. However, both shapes did not gather the best melting and smooth properties, while Round and Rectangle were well delivering on texture (high melting, high smoothness).To better understand the observed differences in texture and especially on melting attribute, we went a step further by exploring
the physical mechanisms underlying the melting sensory attribute in the specific conditions of the test. Differences in perceived melting were expected as we know that modulating the shape plays a role on the heat transfer occurring in the mouth. The dominating heat transfer mechanism is heat conduction across the parts of the chocolate surface being in direct contact with the oral surface (Fig. 6). Thus, a shape with a small initial contact surface area (ex. the Sail) is expected to melt slower than a shape with large contact surface area (ex. Round).In addition, a shape which is compact (e.g. a sphere), will melt slower than a shape which is elongated (e.g. thin plate) since
internal heat propagation depends on the characteristic length of the geometry. The compactness is therefore important to consider for predicting the melting speed of shapes. It is quantified as surface to volume ratio S/V. Keeping in mind that only a part of the total surface of the shape is in contact with mouth elements during