Tribological Method to Measure Lubricating Properties of Dairy Products

Tribology has a growing interest in oral texture and sensory research due to its ability to assess certain properties of the food during the complex oral processing that cannot be explained by its bulk texture and rheology. Developing a reliable, low cost and easy-to-use tribometer applicable to a wide variety of food products is still a big challenge to researchers. In this work, a simple method to measure lubricating properties (friction coefficient) of dairy products is presented using a newly introduced tribometer coupled with a widely used rheometer. Pasteurized milks (fat contents from 0.1% to 4.9%) and cream cheeses (fats content: 0.5%, 5.5%, 11.6%) were chosen as representative dairy products and their friction coefficients were measured as a function of entrainment speed of the tribometer. The friction coefficients of the samples at low entrainment speed generating low shear rate (similar to the shear rate in mouth) were significantly different between the samples at each fat levels. Thus, this method is capable of differentiating samples with different fat contents both in liquid or semi-solid forms. This suggests a promising application of this technique for a quick assessment of the sensory mouthfeel of various dairy products in relation to fat content.