Influence of sound on texture perception of apples

Crispness perception of dry food could be modulated by the sound the perceiver produces while biting into it [1]). Does sound influence crispness perception for wet food (apples) as well? Does sound have an effect for perceived hardness that, unlike crispness [2], is mainly a mechanical parameter? Sixty-two participants, divided in 3 groups, were asked to bite flesh cylinders sampled from apples with different texture profiles and to rate them for crispness or hardness. Crucially, they could hear the sound (realistic or manipulated) produced while biting only through headphones. In experiment 1 (E1), participants rated the perceived crispness of ‘Reinette’, ‘Golden’, and ‘Fuji’ apples. High frequencies of sound (2-20 kHz) were reduced (-12 dB or -24 dB) or fed back without any auditory adjustment (realistic sound). In experiment 2 (E2), perceived crispness and hardness of ‘Reinette’ and ‘Fuji’ apples were rated. The sound was either realistic, or reduced (-24 dB), or globally dampened (microphone off). Experiment 3 (E3) had the same conditions as E2 with the difference that white noise was continuously presented through the headphones. In all experiments, the different apple varieties were correctly discriminated. As for sound manipulation, E1 confirmed its effect on crispness perception: Apples were rated less crispy when both sound reductions were applied than with the realistic sound. In E2, both reduction and dampening of sounds lowered the perceived crispness of apples as compared to the realistic sound. Apples were instead rated less hard with the microphone off than with the real sound. In E3, the effect of sound disappeared for crispness, while it was marginal for hardness: Apples were rated softer only with the microphone off. This research demonstrates that sound affects perceived crispness also in wet foods. It also demonstrates, for the first time, that such effects can be observed also for mechanical sensory parameters. [1] Zampini, M., & Spence, C. (2004). The role of auditory cues in modulating the perceived crispness and staleness of potato chips. J. Sens. Stud., 19, 347-363. [2] Christensen, C.M., & Vickers, Z.M. (1981). Relationships between chewing sounds to judgments of food crispness. J. Food Sci., 46, 574-578