physical property of ice cream that has a major influence on sensory quality in general, and texture assessment in particular, is apparent viscosity. Apparent viscosity in the partially melted state is an important factor because it influences how a sample of ice cream reacts within a person's mouth. The resistance of ice cream to the mechanical forces imparted by the tongue, upper palate and teeth will dictate the overall perception of ice cream texture. Viscosity building has been cited as a general function of carbohydrate-based fat replacers (Akoh, 1998).
In the current study, both the LF and FF samples (Table 3) were viewed as having a significantly lower viscosities; however, the L sample was not significantly different from the regualr fat sample. While Specter and Setser (1994) did not evaluate viscosity as such they did examine wateriness which they describe as melting rapidly, causing a loss of viscosity and the development of a thin and watery perception. In contrast to this study, five of the six treatments evaluated by Specter and Setser were perceived as having significantly higher degrees of wateriness compared to the regular fat (12% milk fat) ice cream. Even the wateriness of the sample which contained 8% milk fat and 4% fat replacer (for both N-Oil® and Paselli SA2) were judged as significantly more watery than the control.
In research by Li et al. (1997), using the polydextrose fat substitute Litesse®, significant differences in apparent viscosity between the regular fat (9.65% milk fat) sample and some of their lower fat (5.63, 2.35 and 0.53%) samples were reported. Their work demonstrated that the use of Litesse® as a fat replacer will affect the apparent viscosity of fat reduced ice creams and the degree to which viscosity is altered depends on the level of fat and total solids. In comparison, the modified starch used for the current study appeared to reproduce the viscosity of the regular fat ice cream as perceived by trained panellists in ice creams reduced to 5% milk fat.