P.W. Cox

Visualisation of three-dimensional flows in rotating cans using positron emission particle tracking (PEPT)

Abstract The flow of foods in cans is critical in determining process times and thus product quality. The flow of liquids has been followed in axially rotated metal food cans using positron emission particle tracking. The technique involved placing a small (≈600 μm) isokinetic radioactive tracer into a container and following its movement with a positron sensitive camera. The small size of the tracer, as well as the ability of the emitted gamma rays to penetrate both opaque fluids and considerable thicknesses metal (≈10 cm) make the method ideal for studying fluid flows inside real equipment. The method enables a spatial resolution of close to one millimetre and a time resolution of a millisecond. Flows have been studied in axially rotated cans filled with Newtonian liquids of differing viscosities and a varying amount of headspace. The inclusion of a headspace in a can caused the flow within the two-phase system of a viscous solution to become inherently three-dimensional with a regular period of circulation and flow trajectory.

Effect of Processing on Biopolymer Interactions

Publisher Summary Various studies have shown that the hydrocolloids that can be influenced by processing to produce new structures and material properties undergo aggregation processes to form bulk three-dimensional gels. The effect of applied forces depends upon the relative timescales and dimensions of the ordering process and the applied mechanical forces. The biggest effect of applied mechanical forces is seen to be on gelation. The presence of charged groups on one of the polymers has a profound influence on the phase behavior. The quality of water-in-water emulsion-based products often depends on the morphology and structure of these mixtures, which in turn strongly depends on the interfacial tension between the two aqueous phases. It is therefore important to understand the phase behavior, rheological behavior, and other factors affecting phase morphology and structure of such systems. The kinetics of digestion depends on the chemical and physical characteristics of food and their interaction with the physiological events occurring within the gastrointestinal (GI) tract. This chapter considers the environment and processes that occur during the digestive process and how these influence or are influenced by hydrocolloids.