Dynamic alternatives to fractal and Fourier methods for analysis of crispy/crunchy food products

Sanahuja, Solange; Briesen, Heiko (2014). Dynamic alternatives to fractal and Fourier methods for analysis of crispy/crunchy food products In: The 3rd international conference on food oral processing - physics, physiology, and psychology of eating. Wageningen, The Netherlands. 29.06.-02.07.2014.

Crispiness and crunchiness of cellular foods like appetizers, fresh fruits, or vegetables are the most important textural attributes examined in food quality control as they have the highest impact on overall consumer appreciation. The breakdown of foodstuffs under mechanical load can be measured by classical mechanical analysis. The resulting force versus time curves show a complex jagged behavior, which is difficult to correlate with textural attributes as evaluated by humans. In this work, we introduce three dynamical measures that could better relate those curve shapes to crispy and crunchy food attributes. A number of relatively simple calculation methods for crispiness and crunchiness, as well as crackliness and rubberiness, are available. Stiffness, fracturability, brittleness and hardness only consider the first breaking event and sometimes can be related to crispiness and crunchiness. Some characteristics account for the multitude of breaking events, like the number of breakage peaks or the linear distance of the curve. There are also more complex analysis methods for mechanical or acoustic signals, which are not yet commonly used in industry. The degree of jaggedness of the curves can be estimated from fractal and Fourier analyses by calculation of the apparent fractal dimension and the mean magnitude of the power spectrum, respectively. However, none of these methods does always reliably predict sensory evaluation results. Moreover, they do not capture the dynamics of breakage during deformation, although the temporal aspect of the sensory feedback strongly influences texture assessment. Due to the limitations of the methods discussed above, Wavelet Transform and Hilbert-Huang Transform (HHT) are proposed as powerful alternatives. They are compared to Windowed Fourier Transform, which has already been evaluated for sound analysis, but has been rarely used in eating-sound studies. These techniques are applied to force-time curves of compression tests of curly peanut chips. Results in the time and frequency domain are shown. The combination of the three methods captures the dynamics of breakage events well. Therefore it is an important supplement to classical analysis techniques. As the interpretation of the obtained time-frequency-energy spectra is difficult, typical characteristics to discriminate different product qualities are proposed and evaluated in this work. Some of the investigated characteristics are the distribution shape of instantaneous frequencies, their corresponding amplitudes or energies, and their evolution in time. These characteristics are shown to be able to distinguish between products of distinct humidity levels. Even if it was not investigated in this study, the methods are also expected to predict differences in crispiness and crunchiness of the products. The relation of such knowledge of the foods evolving mechanical properties to their internal structure (porosity and pore walls matrix composition) would permit to link formulation and processing to resulting product physical and sensory characteristics.

Item Type:

Conference or Workshop Item (Speech)


School of Agricultural, Forest and Food Sciences HAFL > HAFL Continuing education


Sanahuja, Solange and
Briesen, Heiko


Q Science > QC Physics




Solange Sanahuja

Date Deposited:

13 Feb 2020 09:37

Last Modified:

13 Feb 2020 09:37



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