Macauba palm endocarps under compression forces considering the different treatments: A study about physical and mechanical properties for seed extraction

Abstract

Macauba (Acrocomia aculeata) is a palm tree native to the tropical forests of North America and Brazil, with fruits that hold significant potential across agricultural and industrial sectors, including cosmetics, pharmaceuticals, food, and biofuels. The spherical, drupe-like fruit consists of a fibrous peel (epicarp), pulp (mesocarp), endocarp, and seed. The endocarp, housing the seeds, is a dense, mechanically robust triaxial spheroid with high caloric value. To harness macauba potential on an industrial scale, strategies incorporating high-performance machinery are necessary, replacing rudimentary extraction methods with more rational approaches to crop development. Understanding the physical and mechanical properties of such crops is crucial for designing machines and processes for agricultural product cultivation. This study focuses on the mechanical behavior of the macauba palm endocarp for seed extraction, evaluating its geometric and mechanical properties through compressive stress analysis. Geometric properties such as endocarp characteristics, circularity, sphericity, eccentricity, and surface area were examined, alongside the influence of different endocarp treatments on rupture strengths. Compression tests on macauba fruit endocarps revealed treatment methods (control, 24, 48, and 72-h water immersion, and 10-day sun exposure) influence on mechanical properties at various strain rates (100–600 mm.min-1).Results show the macauba palm endocarp behaves as a spheroid. Immersing macauba endocarps in water increased their rupture strength during compression. However, sun exposure for 10 days rendered the fruit more fragile and less tenacious, reducing rupture force by over 40 % compared to control samples. The Deformity Modulus of macauba fruit endocarp ranged from 30.1 GPa to 53.2 GPa depending on the treatment applied.