AN IMPROVED INSTRUMENTAL CHARACTERIZATION OF MECHANICAL AND ACOUSTIC PROPERTIES OF CRISPY CELLULAR SOLID FOOD

Abstract

ABSTRACT A detailed study was performed to simultaneously measure the mechanical and acoustic properties of crispy cellular solid foods. Different critical aspects are discussed in order to assess optimal test conditions. These are primarily data sampling rate, microphone positioning, frequency spectrum of interest, sound/noise ratio and selection of measuring probe. A data sampling rate of more than 50 kHz was shown to be sufficient to register fracture event and acoustic event, and the frequencies audible by human ear (at least 40 kHz needed). The optimum positioning of the microphone with respect to the test piece should be a compromise between a distance that the microphone registers a good sound over the whole human audible frequency spectrum and a good sound/noise ratio. It is shown that test method selection has to depend on whether the goal is determining material fracture behavior or correlation of data to consumer perception. The best method from a fracture mechanics point of view does not have to be the best choice for a combined fracture and acoustic measurement. PRACTICAL APPLICATIONS The method described will especially be useful for the study of materials that fracture in a brittle way whereby during the fracture process, an audible sound is emitted (as is the case for crispy and crunchy food products). Although the data reported are for dry products, the method will be relevant for the study of all kinds of crispy/crunchy products. This work also shows that for a study directed on elucidating the mechanisms determining crispy/crunchy behavior of foods, a much higher data sampling rate is required than used in most studies published in literature. Moreover, guidelines are given for the positioning of the microphone and the selection of the measuring probe for measuring simultaneously the mechanical and acoustic fracture properties of crispy/crunchy cellular solid foods.