Design of a fresh lotus seed plumule removal machine and optimization of plumule removal process parameters

The inherent limitations of manual plumule removal in fresh lotus seeds, primarily its low efficiency and high labor cost, present a significant bottleneck for industrial-scale processing. In direct response to this challenge, this study was conducted to develop a novel fresh lotus seed plumule removal machine based on the air pressure extrusion technology. The developed system is capable of automatically and adaptively processing lotus seeds across a wide range of sizes, thereby establishing a viable solution for enhancing operational efficiency and paving the way for automated industrial production. Based on the requirement of ensuring the relative integrity of lotus seeds and plumule during the debittering process, the paper proposed an air extrusion method for removing the plumule from fresh lotus seeds. It also designed the overall structure of the fresh lotus seed plumule removal machine, along with its key components such as the rolling orientation adjustment device, self-adaptive centering mechanism, and end-recognition device. Firstly, based on the method of dual rollers rotating in the same direction to rapidly adjust the orientation of fresh lotus seeds, this study investigated the influence of roller material and rotational speed on the orientation time. Tests showed that when using polyurethane rollers at a speed of 70 r/min, fresh lotus seeds in any initial orientation could be quickly and precisely positioned. Furthermore, a self-adaptive centering mechanism was proposed that automatically adjusts the position of the debittering punch based on the size of the fresh lotus seed. The optimization of its linkage lengths and positional parameters ensures coaxial alignment between the air needle axis and lotus seed axis across varying seed sizes, achieving a maximum theoretical deviation of 0.036 mm. Finally, the effects of processing parameters such as air pressure, jet duration, air needle aperture and insertion depth on the plumule complete removal rate, damage rate and plumule intactness rate of fresh lotus seed plumule removal were discussed. The optimal processing parameters obtained were air pressure of 0.6-0.7 MPa, jet duration of 50·ms; The inner diameter of the air needle is 2.6 mm, and the insertion depth of 6-8 mm. The field test results based on these optimal processing parameters are as follows: plumule complete removal rate reached 95.8%, the plumule intactness rate was 87.6%, the seed breakage rate was 1.36%, and the process efficiency was 34.8 kg/h. The experimental results collectively demonstrate that the proposed method and machine satisfactorily meet all key processing requirements for fresh lotus seed plumule removal. The research results provide fundamental reference for modeling the mechanical dynamics of air extrusion-based plumule removal, enriching the academic knowledge base in agricultural post-harvest processing. The research directly addresses the long-standing bottleneck of production efficiency by proposing an adaptive automatic fresh lotus seed plumule removal solution. This innovation represents a fundamental shift from traditional manual methods, holding the significant potential to mitigate persistent labor shortages, drastically reduce operational costs, and substantially increase processing yield and consistency. This improvement directly translates to a stronger profit margin and a more reliable supply chain, thereby decisively enhancing the overall competitiveness and economic viability of the lotus seed industry.