The effect of rheological properties of foods on bolus characteristics after mastication.
OBJECTIVE
To evaluate the effects of physical properties of foods on the changes of viscosity and mass as well as the particle size distribution after mastication.


METHODS
Twenty subjects with no masticatory disorders were recruited. Six grams of four solid foods of different textures (banana, tofu, cooked-rice, cookie) were provided, and the viscosity and mass after 10, 20, and 30 cycles of mastication and just before swallowing were measured. The physical properties of foods, such as hardness, cohesiveness, and adhesiveness, were measured with a texture analyzer. Wet sieving and laser diffraction were used to determine the distribution of food particle size.


RESULTS
When we measured the physical characteristics of foods, the cookie was the hardest food, and the banana exhibited marked adhesiveness. Tofu and cooked-rice exhibited a highly cohesive nature. As the number of mastication cycles increased, the masses of all foods were significantly increased (p<0.05), and the viscosity was significantly decreased in the case of banana, tofu, and cooked-rice (p<0.05). The mass and viscosity of all foods were significantly different between the foods after mastication (p<0.05). Analyzing the distribution of the particle size, that of the bolus was different between foods. However, the curves representing the particle size distribution for each food were superimposable for most subjects.


CONCLUSIONS
The viscosity and particle size distribution of the bolus were different between solid foods that have different physical properties. Based on this result, the mastication process and food bolus formation were affected by the physical properties of the food.
Department of Physical Medicine & Rehabilitation, Chung-Ang University College of Medicine, Seoul 156-755, Korea.
Junah
J
Hwang
Don-Kyu
DK
Kim
Jung Hyun
JH
Bae
Si Hyun
SH
Kang
Kyung Mook
KM
Seo
Byong Ki
BK
Kim
Sook Young
SY
Lee
Mastication; Particle size; Rheology; Swallowing; Viscosity