Flavour, texture and satiety

THE CONSUMPTION of liquid calories has been implicated in the development of obesity and weight gain. Energy-containing drinks are often reported to have a weak satiety value: one explanation for this is that because of their fluid texture they are not expected to have much nutritional value. It is important to consider what features of these drinks can be manipulated to enhance their expected satiety value. Two studies investigated the perception of subtle changes in a drink’s viscosity, and the extent to which thick texture and creamy flavour contribute to the generation of satiety expectations.

In study one, participants who were not sensory panellists tasted and rated 16 fruit yoghurt drinks of varying thickness, manipulated by the addition of small quantities of tara gum (0.0 to 0.47g/100g of the drink, increasing in 0.03g increments across the 16 drinks). Rheological measurements were taken and participants rated how thick, creamy, fruity, sticky, sweet and sour each sample was (0 = not at all, 100 = extremely) on two non-consecutive days. Perceived thickness was related to viscosity at a shear rate of ≈50 reciprocal seconds (1/s).

The results of this study indicate that participants were able to perceive subtle differences in drink texture, and these differences were closely related to actual viscosity. This is in line with previous evidence that suggests that viscosity at a shear rate of 50 1/s relates to perceived thickness^[34,35]. Small incremental increases in tara gum across the 16 drink samples produced measurable increases in viscosity (10 to 317 mPa?s, ranging from a fluid juice texture to a thicker yoghurt drink texture, all consumed through a regular straw) and the participants perceived these subtle changes, although probably not at the level of every incremental increase. This sensitivity to subtle differences in viscosity is not surprising because texture is likely to be one sensory characteristic of food that reliably predicts the presence of nutrients, such as fat^[36].

In study two, a new set of participants, who were not trained sensory panellists, evaluated the sensory and hedonic characteristics of eight versions of a fruit yoghurt drink, which varied in thickness (thin or thick), creamy flavour (low-creamy or creamy) and energy content (high- or low-energy). The participants also rated how filling they expected each drink to be (0 = not at all, 100 = extremely) and its expected satiety. In the expected satiety measure, participants indicated the extent to which they eDioni Tabbers