Non-destructive characterisation and quantification of the effect of conventional oven and forced convection continuous tumble (FCCT) roasting on the three-dimensional microstructure of whole wheat kernels using X-ray micro-computed tomography (μCT)

Food microstructure influences the characteristics of end products. X-ray micro-computed tomography (μCT) enables investigating internal structure of food products non-destructively. High-resolution X-ray μCT, in combination with image analysis, was used to visualise and quantify the impact of conventional oven and forced convection continuous tumble (FCCT) roasting (180 °C for 140 s) on the microstructure of whole wheat kernels. After image acquisition, two-dimensional (2D) cross-sectional images were reconstructed into three-dimensional (3D) volumes. Quantitative parameters, i.e. volume, porosity, expansion ratio (ER) and relative density, were calculated. Oven roasting was associated with a significantly (P < 0.05) larger increase in kernel volume (4.47%) than FCCT roasting (1.57%). Porosity was higher in the oven-roasted samples (10.33 ± 4.63%), indicating a more destructive impact on the internal structure (FCCT = 8.29 ± 2.29%). Roasting introduced cavities and cracks within the wheat kernels, resulting in a decrease in whole kernel density (oven = 2.76%; FCCT = 0.55%), however the material density remained unaffected during FCCT roasting.