Application of Uniaxial Compression Curve Fractal Dimension in the Identification of Cañihua (Chenopodium Pallidicaule Aellen) Grain Cultivars

HIGHLIGHTS Grains of three cañihua cultivars were identified through the determination of fractal dimension of its force?deformation curves. A special test cell device was developed to mechanically assess small grains during compression tests. Cañihua cultivars form separate groups when results of fractal dimension of their force?deformation curves, force of rupture, and fracture force are analyzed with PCA. ABSTRACT.Cañihua is an ancient crop of the Andean regions in South America. High genetic diversity of this crop can be found around Lake Titicaca. Cañihua grain is an important source of food for the people in this region because of its high protein and amino acid contents. Currently, there are three known cultivars and more than a hundred accessions of cañihua. Most of the grains from these cultivars and accessions have the same shape and color, making their identification difficult. This work sought to estimate the fractal dimension of force–deformation curves obtained during individual cañihua grain compression tests through the box-counting method (BCM) and the Higuchi fractal dimension (HFD) to show the possibility of differentiating and recognizing cañihua cultivars by taking into consideration the influence of their mechanical properties and chemical composition. Using BCM for the fractal dimension of the force-strain curves allowed us to differentiate the three cultivars from each other, and with HFD, it was possible to observe the difference between accessions and cultivars. Finally, by using the BCM and HFD results, together with mechanical properties such as the bioyield and rupture points and the energy required to reach them, the three cañihua cultivars could be differentiated from the accessions through multivariate PCA. The findings of this work could be applied to distinguish or identify cultivars of different crop grains. Keywords: Cañihua cultivars and accessions, Fractal dimension, Force–deformation curves, PCA.