3D imaging of bean seeds: Correlations between hilum region structures and hydration kinetics

Abstract

X-ray micro-CT imaging has been applied successfully in food science and seed research due to its capacity to provide very small details of seed traits that are very complex to score. The micropyle and the tissues of the hilum region of bean seeds are recognized as structures which play an important role in hydration process. This latter influences, in turn, not only germination but also the cooking and industrial processing. Nevertheless, the role of each structure of the bean seeds is yet to be fully understood. Moreover such traits are never been quantified by using 3D imaging approaches. In this work, seeds of four ancient Italian landraces of beans have been scanned by X-ray microCT with a twofold approach: bulk scans for whole seed imaging and single seed scans for internal traits measurements. Then water uptake tests have been performed. The different structures composing the hilum region of the beans have been imaged and characterized. The two-dimensional and the three-dimensional morphometric traits have been correlated with parameters of hydration models by Principal Component Analysis (PCA) and Pearson coefficients. Micropyle groove area was the trait most influencing the very initial hydration rates while the hilum groove area was the best correlated with the overall infiltration behavior. The internal free space was the trait best correlated with the moisture at equilibrium. Moreover, strophiole shape resulted the most suitable internal trait for univocal identification of the four landraces. Overall results give a contribution to the understanding of the role of hilum region structures in bean seeds hydration process and show novel morphological traits useful for identification of local bean landraces.

Keywords: Bean morphometry; Common bean landraces; Micropyle; Water uptake; X-ray microCT.