Image Analysis of Bread Crumb Structure in Relation to Mechanical Properties

Abstract

Abstract To correlate the mechanical properties with the crumb structure of bread, a simple and objective method of measuring air bubbles of crumb samples was developed using an image scanner and digital image processing. Four images of the sample scanned in four orthogonal directions were aligned and combined to obtain an enhanced image in which air bubble regions were emphasized by min-operation, selecting the minimum gray level among the four images for each pixel. Next, Otsu’s method was applied to threshold each sub-image of the enhanced image in order to quantify the geometries of the air bubbles precisely, and then the black regions of the image were found to be air-bubbles. As a result, the four air-bubble parameters of the bread samples were determined to be mean bubble area, mean bubble perimeter, number of bubbles, and bubble area ratio. In addition, the viscoelastic properties of the samples were measured by the creep test and determined to significantly correlate with the bubble area ratio (r > 0.59, p < 0.05). This indicates that with increasing air-bubble area, crumb hardness increases. The proposed method is inexpensive and easy to operate, and thus is considered to be applicable to the quality assessment in food factories.