Impact behaviour of freeze-dried and fresh pomelo ( Citrus maxima ) peel: influence of the hydration state

Abstract

Pomelos (Citrus maxima) are known for their thick peel which—inter alia—serves as energy dissipator when fruits impact on the ground after being shed. It protects the fruit from splitting open and thus enables the contained seeds to stay germinable and to potentially be dispersed by animal vectors. The main part of the peel consists of a parenchymatous tissue that can be interpreted from a materials point of view as open pored foam whose struts are pressurized and filled with liquid. In order to investigate the influence of the water content on the energy dissipation capacity, drop weight tests were conducted with fresh and with freeze-dried peel samples. Based on the coefficient of restitution it was found that freeze-drying markedly reduces the relative energy dissipation capacity of the peel. Measuring the transmitted force during impact furthermore indicated a transition from a uniform collapse of the foam-like tissue to a progressive collapse due to water extraction. Representing the peel by a Maxwell model illustrates that freeze-drying not only drastically reduces the damping function of the dashpots but also stiffens the springs of the model.

Effects of post-drying methods on pomelo fruit peels

“…Oven-dried albedo with a content of 5.88% showed a significantly (p<0.05) lower moisture content than freeze-dried albedo at 8.63%, lower values than for pomelo albedo reported by Zain et al 3, and for lemon albedo (23). Thus, oven drying method contributed to rapid removal of water from air filled intercellular spaces of albedo (24), reducing the moisture content.…”

Pomelo Peel-Inspired 3D-Printed Porous Structure for Efficient Absorption of Compressive Strain Energy

“…For example, the thick pomelo peel can dissipate energy up to an impressive ~ 98 J, allowing the fruit to withstand a deceleration force of several kilonewtons without visible damage [4,5]. The porous structure in pomelo peels is considered to be responsible for the ability of energy absorption [5][6][7][8][9][10]. However, a quantitative understanding of how the porous structure enables the high energy absorption across different pomelo varieties remains missing.…”

Morphological evolution and internal strain mapping of pomelo peel using X-ray computed tomography and digital volume correlation

“…Among numerous natural materials, pomelo peel, a foam-like fiber-reinforced biological tissue, is capable of dissipating considerable kinetic energy when hitting the ground after falling from the tree, thus providing guidance for developing lightweight impact resistant materials via establishing hierarchical structure [10][11][12]. To understand the biomechanical mechanism of pomelo peel, research efforts have been dedicated to reveal its deformation response [13], mechanical behavior [14] and structure-function relationship [15] in 2D case. However, due to their complex multiple-scale microstructure and non-linear mechanical properties, surface analysis is insufficient to reveal the internal mechanisms of deformation and dissipation.…”