An Improved Instrumental Characterization of Mechanical and Acoustic Properties of Crispy Cellular Solid Food

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.

Texture measurement of potato chips using a novel analysis technique for acoustic vibration measurements

“…In addition, for a full understanding of food texture, Tesch, Normand, and Peleg (1996) stated that there must be an understanding of how mechanical failure occurs as well as of the resulting sound waves that occur with this failure. A method for simultaneous measurement of compression force and sound pressure could provide information on detailed fracture mechanism (Castro-Prada et al, 2007). In this case, slow cutting experiment is preferable because it allows to distinguish each fracture event in the time domain (Luyten & Van Vliet, 2006).…”

“…They emphasized using engineering approaches that enabled the detection of different levels of crispness. Recent methods simultaneously measured both the compression force and the sound pressure when a solid food was being fractured (Castro-Prada, Luyten, Lichtendonk, Hamer, & Van Vliet, 2007;Chaunier, Courcoux, Della Valle, & Lourdin, 2005;Chen, Karlsson, & Povey, 2005;Salvador, Varela, Sanz, & Fiszman, 2009). This method is essentially the same as the above-mentioned method used by Vickers (1987): a combination of acoustic and forcedeformation measurements.…”

“…The acoustic events also corresponded to the second derivative of the force-deformation curve, indicating the rate of energy released during fracture events. Castro-Prada et al (2007) characterized the experimental setup for the simultaneous measurement of the mechanical and acoustic properties of crispy cellular solid foods. They pointed out that the measurements depended on the data acquisition conditions such as sampling rate, microphone position, and signal-to-noise ratio.…”

On the assessment of fracture in brittle foods: The case of roasted almonds

“…This low resolution added to the fact of the inertia effects of the measuring system already discussed, made some of the fracture events or peaks were probably missed, so a data acquisition rate of 500 ps resulted in a less accurate measurement of the force signal at the higher test speed. This fact is discussed in detail in a recent paper by Castro-Prada et al (2007). This is an important point to be subject of further study, as the SMS TAXT2 Texture Analyser is one of the most common devices used for texture assessment both in food research and in the industry nowadays, and although it has very good features in general, it seems to be limited in terms of characterizing some aspects of crispy/crunchy food.…”

Examination of optimum test conditions for a 3-point bending and cutting test to evaluate sound emission of wafer during deformation

“…Product Bella were used to investigate best microphone position by applying 3-point bending at 1.0 mm/s test speed. Two deformation methods were used to investigate crispness of wafer samples; 3-point bending (Alvarez, Saunders, Vincent, & Jeronimidis, 2000;Baltsavias, 1996;Castro-Prada, Luyten, Lichtendonk, Hamer, & Van Vliet, 2007;Chen et al, 2005) and cutting test methods (CastroPrada et al, 2007). For the 3-point bending, the sample lays on two supports and a compressing IJFS April 2018 Volume 7 pages 13-23…”