Abstract
The aim of this research was to improve the understanding of oral texture perception. In particular to examine the role of oral physiological processes on oral texture perception of semi-solids and to investigate whether individual differences in perception could be attributed to differences in oral physiology among subjects.
The main
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results reveal that:
• Large intra-individual differences in oral physiology and sensory ratings were confirmed.
• Oral size perception results from a combination of sensory inputs from the palate and the tongue. Size itself determines the size perception of single objects, while material and weight are negligible factors.
• For particles mixed into a medium, size and type of particle influenced size perception, which is suggested to be mediated by vibration. Soft and round particles are perceived as smaller than hard and irregular particles.
• The two methods - direct-scaling and forced ranking - produce similar results on size perception.
• Some measurements of oral sensitivity correlate, such as masticatory performance and size perception of spheres. Subjects who are poor chewers are more sensitive to particles in sizes which could cause then discomfort on swallowing.
• The natural volume of saliva did not affect the texture perceptions, presumably because the subjects were used to their inherent levels of saliva. In contrast, a change in the natural amounts of saliva, realized by an artificial addition of saliva or saliva related fluids, did affect attributes related to dilution and breakdown of the product, such as thickness and melting.
• The composition of saliva exhibited correlations with the perception of numerous texture attributes. The fractions of solubles in the saliva, many of which have enzymatic, lubricative or other actions important for mastication, do seem to be important for the perception of semi-solids. Accordingly, the attributes for custard dessert, which is thickened mainly by starch, were especially sensitive to the activity of amylase and proteins.
• The sensation of virtually all flavour and mouth-feel attributes requires at least some tongue movement. Most attributes showed a similar pattern, with lowest attribute ratings where the tongue’s movement was restricted and gradually increasing ratings with increasing complexity of the tongue movements. An individual’s normal mastication behaviour, which exhibited the largest diversity and complexity of movements, typically resulted in the most intense sensations of flavour and mouth-feel. This suggests that consumers aim to maximize their food sensations.
• The addition of particles to a custard dessert had large effects on perception of the texture attributes. Roughness increased with increasing particle size and hardness, while smooth, slippery, creamy and fatty decreased, irrespective of type of particle. Very small particles (2 µm) also have strong effects on the perception. Subjects who perceive particles of a certain size to be large, do not perceived that same stimulus to be rough. Hence, particles need to be sufficiently small to be considered part of the stimulus.
• The primary result of an increase in stimulus temperature probably was the decrease in stimulus viscosity, which was reflected in decreased perception of thickness. With the decrease in viscosity, a number of secondary effects were observed, such as facilitated migration of fat to the surface of the product, resulting in more fatty sensations.
The results demonstrate that the oral physiological parameters oral sensitivity, tongue movements, temperature and saliva composition are of importance for texture perception of semi-solids. Many parameters of oral physiology correlated with various texture attributes. This implies that intra-individual differences in texture perception could be attributed to variations in oral physiology. Oral physiology thus plays a role in texture perception of semi-solids and should be taken into account in future texture research.
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