Crispiness is one of the sensory properties on which humans base their appreciation of certain food stuffs. It is perceived by a combination of auditory, tactile, kinaesthetic, and visual sensations – and when crispy food is chewed the movement of the jaw tends to change due to resistance and breakage of particles.
The study, which has been accepted for publication in the journal Food Quality and Preference, was conducted in Utecht, The Netherlands and Sao Paolo, Brazil. It set out to investigate the influence of auditory and/or visual information on the perception of crispy food and on the physiology of chewing. It adds to understanding about the eating experience in different environmental conditions.
The study involved 24 healthy participants (13 men and 11 women) aged between 19 and 41 years, all of whom had their own teeth at least as far as the second molars, and who had no major dental problems.
During a 90 minute tasting session the participants were asked to chew and swallow normally three different types of fresh biscuits, whose crispiness had been adjusted by altering the water content.
Each biscuit type was chewed twice per masking condition block: with auditory masking; with visual masking; with both visual and auditory masking; and with no masking.
The auditory masking consisted of loud sounds of breaking crispy food being played over an open microphone. The visual masking consisted of participants having their eyes closed, and the researchers placing the samples in their mouths.
The researchers measured the jaw gape as the participants chewed using infrared light-emitting diodes on the chin and the forehead. Movement signal determined the number of chews until swallowing, and skull vibration was measured using an accelerometer placed next to the skin by the mastoid bone, by the right ear.
The researchers found that participants who started the series of experiments with both auditory and visual masking were more influenced by auditory masking in their chewing, whereas those who had already received visual or auditory clues were not.
“Our research confirm previous findings suggesting that visual clues had no effect on loudness or pitch judgement,” they wrote.
The team concluded that bone conduction of the vibrations of the breakage of food, propioception (the ability to sense and orientate movement of the body) and tactile sensors may supply sufficient information to the brain to control the chewing process when auditory information is lacking.
Food Quality and Preference (online ahead of print)
The influence of auditory and visual information on the perception of crispy food
Authors: Rafael de Liz Pocztaruk, Jan Hendrik Abbink, René A. de Wijk, Luis Carlos da Fontoura Frasca, Maria Beatriz Duarte Gavião and Andries van der Bilt