Abstract
This study examines the strength characteristics of pine nut shells to enhance kernel extraction efficiency. Current methods have drawbacks, including high kernel damage, preheating, and excessive energy use. Laboratory tests using the ST-2 structural meter analyzed the shell's mechanical and rheological properties under varying moisture conditions. The most effective shell-breaking method without kernel damage (for nuts 10.8–11.4 mm in diameter) involves a 90° cone indenter at a shell moisture level of 16–17 %, with an average breaking force of 7.0 kg. Mathematical modeling determined that under an impact force of 49 N and deformation of 1.1–1.3 mm, the required fracture energy is 0.245 J. Finite element analysis in Inventor software confirmed a pre-fracture displacement of 0.016 mm, with stress uniformly distributed across the shell. A pendulum-based test rig studied shell fracture under impact loads. The optimal cracking mode was achieved with an impact mass of 40–60 g at a velocity of 35–40 m/s. A grooved impact surface (90°) with an L/D ratio of 0.4–0.6 reduced fracture energy by 10–15 %. Pre-acceleration in an air stream before impact caused the least kernel damage, but low aerodynamic resistance limited efficiency. To address this, a new device was developed, combining a rotating toothed disk for initial acceleration with a compressed air stream to achieve an optimal velocity of 35–40 m/s. This approach increased whole kernel yield by 15–20 %, reduced energy consumption by 10 %, and minimized product damage. The proposed method improves pine nut processing by increasing efficiency, reducing waste, and lowering costs. It is applicable in food and pharmaceutical industries for optimized kernel extraction while preserving product integrity