Particle size of solid food after human mastication and in vitro simulation of oral breakdown.

Mastication, the first step in food digestion, results in the breakdown of solid food and its lubrication with saliva. Although the rate and extent of starch digestion are closely dependent on the way food is chewed, this factor has not been adequately considered in the preparation of food for in vitro digestion experiments. The purpose of this study was to determine the size distribution of starchy food particles before swallowing and to use an in vitro mincing procedure to simulate how food is divided up during chewing. Foods differing in texture and size (bread, spaghetti and tortiglioni) were chewed by 12 healthy subjects and spat out before swallowing. Chewing time and saliva impregnation were measured for each mouthful. The particle sizes resulting from experiments with chewed and minced bread and pasta were analysed respectively by light laser diffraction and image analysis. Chewing time was longer for bread than pasta, resulting in higher saliva impregnation. Chewed bread showed a bimodal distribution of particle size (30 microns, 500 microns), whereas both kinds of pasta produced particles of similar size (0.5 to 30 mm2) after mastication. Mincing reproduced the division of bread and pasta as achieved by chewing in an acceptable way. From our results it seems that the size of particles resulting from mastication depends on food texture. We succeeded by wetting and mincing food to prepare food in a similar bolus-like form before swallowing. Mincing provides a simple means of simulating the reduction of food into particles for in vitro digestion studies.