Three dimensional characterization of micronized soybean seeds using X-ray microtomography

Abstract

The efficacy of critical processing techniques, such as micronization, relies on the microstructural changes that take place in foods as they go through the various unit operations. X-ray microtomography or computed microtomograhy (μCT) can serve as a means to non-invasively and non-destructively characterize the complex structure of food matrices. Herein, high resolution X-ray μCT was used to visualize and quantify the effect of micronization or infrared (IR) treatment on the microstructure of soybeans at different micronization durations (60, 90, and 120 s), and initial moisture contents (12, 16, 20, and 24% wb). The study includes a quantitative and qualitative analysis of soybean microstructure using 2D and 3D images to assess total porosity, volumetric changes, bulk and particle densities, drying rate, and colour. All of these parameters showed significant changes as micronization time and initial moisture content increased. Although higher initial moisture contents (20 and 24%) improved volumetric expansion and total porosity of soybean kernels, formation of large surface cracks and darkening due to IR heating rendered 24% moisture content unsuitable. Soybeans with an initial moisture content of 20%, subjected to 90 s and 120 s of micronization showed comparable lightness L*values (63.23 ± 3.9 and 61.1 ± 4.1, respectively) to the unprocessed soybean (67.22). These beans also showed the minimal increase in open porosity (5.72–6.06%) but an appreciable increase in total porosity (9.8–11%) was noticed. The results of this study on microstructure and qualitative parameters of micronized soybeans could be used to further optimize the microwave assisted roasting and drying processes of beans and pulses.