Walnut Fruit Processing Equipment: Academic Insights and Perspectives

Abstract

The walnut varieties in China are rich, the planting area in the country is wide, and the yield ranks at the forefront of the world. Walnut kernel is the most important application part of the walnut fruit. An in-depth study found that the by-products of walnut, such as green husk and walnut shell, also have great application potential and are cheap raw materials for the extraction of important medical ingredients and the production of industrial products. However, the by-products are often burned or discarded as waste during processing, which not only wastes resources but also causes environmental pollution. To realize the high value-added application of the walnut fruit, a deep processing of each part of the walnut should be considered. Preliminary processing is the key link before walnuts enter the field of intensive processing and consumption. The advanced level of the required technological equipment can help to determine the quality of the walnut products. The preliminary processing of walnuts in China is mainly divided into six steps: green husk removal, walnut drying, walnut size classification, walnut shell-breaking, walnut shell–kernel separation, and walnut kernel skin removal. This paper starts with a presentation of the importance of each link and the existing bottleneck. Then, the paper systematically discusses the analysis of the current situation and the development of devices required for each link. The working mechanism of each link type and its influence on the design of a corresponding device are summarized. On the basis of the corresponding working mechanism, this study classifies and summarizes the characteristics of the core mechanism of the devices for each preliminary process link; then, it evaluates and analyzes the existing typical mechanical devices according to their types. Finally, the influence rule of the various devices for each link in the preliminary processing is analyzed as a means of ensuring high-quality walnuts.