Applications of Tribology in Studying Food Oral Processing and Texture Perception
Oral texture is one of the most important quality attributes that contribute to consumers’ acceptance and preference of a food product. Oral processing of food is intricate and involves a series of processes—ingestion, mastication and finally swallowing. The mechanical and rheological properties have been widely applied to understand and describe in-mouth flow properties of a food and associated sensory perception. However, as the oral processing continues and food particle size reduces, rheology alone is no longer effective in explaining the textural and mouthfeel properties of food, but the lubrication behaviour between oral surfaces becomes a dominating mechanism in relation to food texture and mouthfeel. For this reason, tribology is emerging as a new discipline for food texture studies, where lubricating properties of food are measured by using an equipment that operates on the same principle used in mechanical engineering for determining the frictional properties of lubricants. While there are many instruments and equipments available for engineering lubrication studies, choice is limited for food applications. This article will review various tribological systems currently utilised for various food systems, whether commercially purchased, custom-made, or by use of attachment tools for rheometers. The operation principles, advantages and disadvantages of these devices are discussed. Examples of food application are also given in each case, where measured frictional properties are used to interpret sensory mouthfeel properties.