The Evolution Of Particle Distribution And Mechanical Properties Of Bolus During Human Mastication

Food bolus is the product during human chewing process. Studying and analyzing its performance evolution before swallowing is one of important issues in the food texture science and oral physiology research. An in-depth understanding about the interactions between the human body and the foodstuffs will provide the basic data for the study of food sensory evaluation mechanism. Meanwhile, it might also be employed to design right food structures that are suitable to the people having the masticatory difficulty or swallowing disorders to improve their chewing efficiency of and swallowing safety.This study choices peanut, celery, apple, cucumber and ham style sausage as experimental materials and five young students as experimental subjects. Firstly, the compressive strength and fracture energy of these materials were measured by means of the mechanical tests. Then the swallowing threshold and the amount of mouthful food were determined for the food materials mentioned above through the actual chewing experiments. The boluses at the different chewing stage were obtained from the first bite till swallowing. The particle-size distribution and the moisture content of the chewed food were determined by sieving and drying. The maximum resistance and the force-displacement curves of the boluses obtained were measured by the small square-bar penetrating test using the universal testing machine. Afterwards, the works were focused on: 1) the agglomerated morphology and the changes of the moisture content of the food bolus during the mastication; 2) the quantitative relationships of the particle mass fraction, the cumulative mass fraction and median particle diameter of the food boluses with chewing cycles; 3) the variation trends of the penetrating force-displacement curves and the work used with chewing cycles; 4) the particles distribution, the moisture content, the morphology and the mechanical properties of the swallowable food bolus. The results show that:1. When same food sample is chewed, the particle size distribution and water content of the food boluses obtained from different subjects are nearly same in the same chewing cycle. For the all test materials, there is a power-law relationship between the median values of the grain diameter and chewing numbers. Also there are close negative correlation between the size reduction rate and the original mechanical properties of the food materials.2. Except the swallowing stage, the penetrating force peak and the work used of the bolus for all kinds of foods are very scatter, but they increases with the increasing chewing cycle basically. After a certain chewing cycle, a more stable state are reached. For the all subjects, the penetrating force-displacement curves of the swallowable bolus for the same food material are similar. The shape and the enclosed area with horizontal axis depends only on food type. The self-stacking height of the food bolus and the work down by the penetrating force have the same varying trend.3. Swallowing activity occurs depends on whether the food bolus has the best aggregative state and lubrication. The formation of the swallowable bolus for the different foodstuffs have different requirements on its own particle size distribution, moisture content and mechanical properties.