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The perceived in‐mouth thickness (T) of a range of fluid foods and model systems was assessed by a trained sensory panel, using a ratio scaling technique, and correlated with objective measurements of viscosity (ηN). For Newtonian samples a simple linear correlation (r2= 0.98) is observed between log T and log η with exponent η= 0.22. The linear relationship between log T and log η for Newtonian materials was used to calculate the equivalent Newtonian viscosity (ηN) from subjective panel scores for the non‐Newtonian samples studied. The shear rate at which observed viscosity is equal to ηN decreases with ηN, as reported previously by Shama and Sherman, but also decreases with increasing shear‐rate dependence of viscosity. This implies oral perception of viscosity over a range of shear rates. Comparison of flow curves for samples assigned similar thickness scores, but showing very different shear thinning behaviour, suggests that the perceived thickness of extremely shear‐thinning materials is dominated by their high viscosity at low rates of shear. As a simple practical index, viscosity at 10 s−1 shows a better correlation (r2= 0.95) with the perceived thickness of the samples studied than values calculated by the methods suggested by Wood, or by Shama and Sherman (r2= 0.90 in both cases). The close agreement between panel scores for perceived thickness and perceived stickiness previously observed for concentrated solutions of random coil polysaccharides does not apply for several of the food systems studied, or for very concentrated solutions of xanthan.

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The binding of sodium myristate to amylose has been studied by a surface tension method. Surface tensions of myristate solutions were compared with those of systems containing amylose. Slow adsorption of amylose-myristate complex at the air-water interface has rendered possible the use of surface tension for estimating mean activities of sodium myristate in the presence of amylose and the construction of a binding isotherm. Information has also been gained on the "surface activity" of complexes. Comparison of the isotherm with optical rotation studies has revealed that a relatively low level of binding can fully induce a conformational transition in the amylose to a helical state. Moreover, this state remains unaffected by the subsequent binding at free myristate approaching the critical micelle concentration. Optical rotation studies together with measurements of surface activity of the complex provide supportive evidence for more than one type of binding process. A cooperative mode of binding is inferred for low free myristate with selective binding to the helical conformer. The cooperative constants and saturation binding for this mode, estimated on linear Ising theory, conform to a model of interrupted but extensive end-to-end packing of extended myristate molecules in the cavity of an amylose helix with six residues per turn. The secondary binding is also cooperative, reflecting lateral hydrophobic attraction between adsorbed myristate molecules and free energies of binding approaching that of micellization.