Relating particles and texture perception.

Practically all foods contain particles. It has been suggested that the presence of particles in food may affect the perception of sensory attributes. In the present study we investigated the effect of size and type (hardness and shape) of particles added to a CMC based vanilla custard dessert. The two types of particles included in the study were silica dioxide and polystyrene spheres, varying in size from 2 to 230 microm. Eighteen trained adults participated in the study. They rated the sensation of 17 sensory flavour and texture attributes on a 100-point visual analogue scale (VAS). The results indicate that the addition of particles increased the sensation of roughness attributes and decreased the ratings of a number of presumably favorable texture attributes (smoothness, creamy, fatty and slippery) significantly. These effects increased with increasing particle size up to 80 microm. Roughness ratings deceased for larger particles sizes. Surprisingly, even particles of 2 microm had significant effects: they increased perceived rough lip-tooth feel, and decreased slippery lip-tooth feel and smoothness of the product. The affected attributes had previously been related to lubricative properties of foods. Particles added to semi-solid foods with relatively low levels of fat seem to counteract the lubricating effects of the fat resulting in increased oral friction. In a separate study on size perception the silica dioxide particles were used. By sampling the stimuli between the tongue and palate, subjects rated the size of the particles on a 100-point scale in comparison to anchor stimuli containing no particles and particles of 250 microm. The perceived particle size significantly increased for larger particles. Furthermore, perceived particle size was negatively correlated with roughness ratings. Thus, subjects who were sensitive and perceived the particles as being relatively large reported the same stimuli to have less rough after-feel. In conclusion, particles added to a product induce large effects on texture sensations, and texture sensation is related to individual size perception.

A comparison of the effects of added saliva, alpha-amylase and water on texture perception in semisolids.

The effect of adding saliva or a saliva-related fluid (alpha-amylase solution and water) to custard prior to ingestion on the sensory ratings of odour, flavour and lip-tooth-, mouth- and after-feel sensations was investigated. Saliva had previously been collected from the subjects and each subject received his/her own saliva. Sixteen subjects from a trained panel assessed 17 flavour and texture attributes of soy- and milk-based custard desserts. Immediately prior to administration, two different volumes (0.25 and 0.5 ml) of three different saliva-related fluids (saliva, alpha-amylase solution and water) were added to the product. The added volumes represented an approximately 33% and 66% increase of the volume of saliva present in the mouth during ingestion. The results show that addition of a fluid affected the mouth-feel attributes of melting, thickness and creamy. Melting was the only attribute on which the type of fluid had an effect, where saliva elicited a stronger melting effect than the alpha-amylase solution and water. The volume of the added fluid affected a number of attributes (thick and creamy mouth-feel and fatty after-feel). It can be concluded that in general the sensory attributes of semisolids were relatively stable. Mouth- and after-feel sensations were partly affected, while odour, flavour and lip-tooth-feel sensations were not affected by an increase in volume of saliva or other saliva-related fluid during ingestion.

Oral movements and the perception of semi-solid foods.

Here we review the role of oral movements in the perception of food attributes, particularly for semi-solid and liquid foods ingested almost in ready-to-swallow form. An overview of a series of instrumental and sensory studies suggests clear links between the type of sensation and the time point of processing in the mouth. Some commonly-reported sensations, such as thickness, are relatively immediate and reflect the bulk properties of food bolus when the food is relatively intact. Others, such as fattiness and melting, reflect both bulk and surface properties and follow considerable oral processing when the food is relatively degraded. Yet others, such as fatty after-feel, are only fully developed after swallowing is complete. In addition, oral processing also plays an important role in the generation of aroma and taste sensations. Most of these in prior vivo studies have now been confirmed by in vitro work using a modified rheometer, dubbed the Structure Breakdown Cell (SBC), wherein the mechanical and enzymatic break-down of food can be monitored directly and related to sensory profiles generated by trained panelists.

The effect of oral temperature on the temperature perception of liquids and semisolids in the mouth.

This work examined the influence of oral temperature on oral perception of temperature in liquids and semisolids. A panel of 20 adults assessed the temperature of water, custard dessert and mayonnaise. Oral temperatures were manipulated by 5-s mouth rinses of 10, 35 and 55 degrees C performed prior to assessments, which resulted in oral temperatures of 27, 35 and 43 degrees C, respectively. The products were evaluated at 10, 22 and 35 degrees C. Results show that subjects were able to differentiate between the product temperatures. A large effect of type of product was seen on perceived temperature, where water was, overall, perceived as significantly colder than custard dessert and mayonnaise. The range of perceived thermal ratings was widest for custard dessert, followed by water and mayonnaise. This might be due to differences in composition and structure of the products. Even though oral temperature was varied considerably in the present study, this did not exert large effects on perceived temperature.

The effect of oral and product temperature on the perception of flavor and texture attributes of semi-solids.

This study examined the effect of oral and product temperature on the perception of texture and flavor attributes. A trained panel assessed 21 texture and flavor attributes in one high-fat and one low-fat product of two semi-solids: custard dessert and mayonnaise. The products were evaluated at 10, 22 or 35 degrees C in combination with oral temperatures of 27, 35 and 43 degrees C. Results showed that modulation of product and oral temperature had significant effects on a number of attributes. Flavor intensities, melting mouth feel, and fat after feel increased, while subjective thickness decreased with increasing product temperature. Neither product- nor oral temperature had an effect on over-all creaminess. Oral temperature affected a number of mouth feel attributes: melting, heterogeneous and smooth. Furthermore, large differences existed in ratings between the high- and low-fat products of custard and mayonnaise, and they were more prominent in mayonnaise. We conclude that the effect of oral temperature on the perception of sensory attributes in semi-solids was small, but present, while the product temperatures influenced the ratings greatly.