Tribology as a Tool to Study Emulsion Behaviour in the Mouth - Food Colloids: Self-Assembly and Material Science - page 452

Oral
processing
& physiology

Oral
proce ssi ng
& physi ology

Oral
proces sing
& ph ysi

Oral
proces sing
& ph ysio logy

logy

Emulsion
engineering

Em ulsion
enginee ring

Sensorial
evaluation

Se nsor ial
evaluat ion

Figure 1 General product development scheme for a food system

the mouth, we should be better able to engineer food emulsions with the desired
creamy in-mouth sensation.

31.2 Sensory Perception of Emulsions
What determines the positive creamy sensation of an oil-in-water emulsion?
There has been a lot of study and controversy on this matter. Many studies
have attempted to relate fat-related attributes like creaminess and fattiness to
chemical and rheological properties of emulsions. It has been shown that
creaminess perception is related to emulsion viscosity, thin film rheology, and
release of fat-associated flavours, and that these factors are interrelated.
Kokini 3 investigated several commercial products and indicated that there is
a mathematical relationship between the perceived thickness, smoothness, and
the creaminess of a product. This suggests that the perception of creaminess is
partly related to the viscosity of a product. Moore et al. 4 confirmed such a
relationship, but pointed out that there are also additional features of emul-
sified fat, which contribute to its perception. Frost and co-workers 5 tried to
enhance the fat perception of a low-fat milk by adding thickener, whitener,
aroma, and by varying the droplet size. Addition of a thickener increased the
viscosity but it did not significantly increase the perception of creaminess. In
another type of study, Richardson et al. 2 compared ratings of overall liking of
food emulsions with creaminess ratings; they also could not find a relationship
between viscosity and creaminess. On the other hand, Akhtar et al. 6 did
conclude that viscosity was of utmost importance to creaminess perception.
Evidence that viscosity alone cannot explain a creamy and fatty sensation of
food emulsions was assessed from an unusual type of food research. By
monitoring neuron signals of the brain of a rhesus macaque, the researchers
showed 7-9 that viscosity and fat can be perceived independently. Researchers
studying the effect of volatiles on emulsion perception elaborated this finding.
They indicated that not only mouthfeel, including the sensation of thickness, is
of importance for creamy sensations, but also flavour release. 1-2,8,9,10 The data