Understanding the effect of structure, composition, and particle size on the oral tribology of solid, semi-solid and liquid dairy foods

Abstract

The tribological behavior of foods is a useful tool that can be used to predict the extent of breakdown during oral processing and the overall sensory perception. This study investigated the effects of food structure, particle size and normal forces applied on the tribological behavior of solid (Cheddar, cheese curd, parmesan), semi-solid (cottage cheese, ricotta cheese, yogurt) and liquid (milk, whey protein beverage) dairy products. At first, 1 g of each sample was equilibrated to 22 °C for 30 min and heated up to 37 °C in a water bath for 5 min and mixed with water for 2 min before loading onto the MCR-302 Anton-Paar rheometer for tribological testing using polydimethylsiloxane (PDMS) pins. Different food structures exhibited a clear distinction in tribological behavior i.e., Stribeck curve indicating friction factor (μ) at several sliding speeds. The peak μ decreased with increasing normal forces due to better mixing of lubricant upon particle size reduction and fat release. The μ for milk was 1.5 at 0.01–0.1 mm/s sliding velocity, significantly higher (P < 0.05) than cottage cheese and solid cheeses attributing to higher moisture content. Semi-solids had the second highest μ of 0.54 at 0.1 mm/s of sliding velocity (P < 0.05). This could be attributed to the differences in fat, moisture, and protein contents of the products. This study reveals that structural differences in various dairy products influence tribological behavior which impacts the texture and sensory perception and release of nutrients in GI tract.