| During food oral processing,the consumer’s preference for food mainly depends on its perception of food texture properties.In the later stages of food oral processing(smaller scales),oral tribology can be used to explains the mechanisms of food texture properties sensory by studying the frictional behavior between two contact surfaces.In oral tribology study,in addition to considering the thickness of lubricating layer and relative slip velocity between two contact surfaces,it is also necessary to consider the nature of contact surface itself,especially the microstructure and properties.The purpose of this study was to obtain threedimensional data of human tongue surface and explore the effects of human tongue surface topography on oral friction and sensory perception by using the laboratory’s self-designed in situ oral friction test device.The main research contents and conclusions are as follows:(1)Human tongue surface microstructure was obtained by double moulding method,3D data of moulding was obtained by optical scanning and surface roughness of human tongue was calculated according to international standard(ISO 25178).The feasibility of double moulding method was verified by obtaining the surface microstructure of hard material(Specimen of standard surface roughness)and soft material(fresh pig tongue).By comparing the "mechanical strength" of impression material with fresh pig tongue,it was determined that the deformation during the moulding process is mainly carried out by impression material.By analyzing the surface roughness of volunteers’ tongue,it was found that the topography of tongue surface was individual.The results show that,in the range of 35 mm in front of human tongue,the distribution of tongue surface roughness(Sa)was from 50 μm to 160 μm and the main distribution was from 60 μm to 80 μm.For the same individual,the surface roughness(Sa)of different tongue areas were not uniform,it was decreasing from front to back and the surface roughness of left and right sides were symmetrical;(2)Recruiting volunteers whose tongue surface roughness were known,in situ friction coefficient was measured by in situ oral friction test device with no food ingesting and after ingesting fluid foods with different fat contents or polysaccharide concentrations.Sensory test of smoothness and in vitro friction test were performed.The results show that with no food ingesting,the in situ friction coefficient has a linear positive correlation with tongue surface roughness(Sa),negative correlation with shear viscosity of lubricating film(saliva)and no significant relationship with the content of total protein and saliva flow rates.After food ingesting,in situ friction coefficient increase and there is a positive correlation between in situ friction coefficient and tongue surface roughness(Sa),but the correlation is weakened.After ingesting samples with different fat content,there is a linear negative correlation between smoothness score and in situ friction coefficient.The lower the in situ friction coefficient,the higher the smoothness score;(3)Recruiting volunteers whose tongue surface roughness were known,in situ friction coefficient was measured by in situ oral friction test device with no food ingesting and after ingesting different size particle solutions.Sensory test of graininess and in vitro friction test were performed.The results show that there is a linear positive correlation between the enhancement degree of graininess and surface roughness(Sa)after ingesting foods.After ingesting foods with different particle sizes,the in situ friction coefficient increases significantly and graininess score had a positive linear relationship with the particle size.The in situ friction coefficient has no significant correlation with food particle size.The results of in vitro simulated friction experiments show that there is a weak correlation between graininess and in vitro friction coefficient,which indicates that perception of graininess in mouth may be affected by other factors. |
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