Hardness sensitivity: Are old, young, female and male subjects all equally sensitive?

Although hardness is a key texture attribute which plays an important role in food preferences, there are no well-established methods to assess human sensitivity to the attribute as perceived in real food product evaluation. The aim of our study was therefore to ascertain whether our previous approach used to estimate sensitivity to graininess could be applied to assess sensitivity to other texture properties, especially hardness. Four jelly samples were prepared with different agar-agar concentrations in order to obtain different levels of hardness. First, mechanical tests were performed to characterize the samples. The jellies significantly varied in hardness, with stress values (kPa) increasing linearly with increasing agar-agar concentration. In all, 248 subjects evaluated both their liking for jellies and their hardness intensity. The hardness intensity evaluated by each consumer was then fitted by a linear equation. Subjects were finally clustered into three groups (high, moderate and low sensitivity) on the basis of the slope of the linear equation and the R squared value. A significant difference between the three groups in terms of perceived hardness (p < 0.0001) was observed, demonstrating the validity of the approach for clustering the subjects. Different sensitivities slightly affected liking scores as well. Young subjects are more sensitive than adults, and males more so than females. In conclusion, we find that differences in hardness perception exist and the proposed approach is useful to gauge them. Moreover, we find that individual characteristics, such as gender and age, may play an important role in hardness perception and food liking.