核桃副产物加工关键技术与装置研究现状

Research status of key technologies and devices for walnut by-products processing

我国核桃种植面积和产量居世界首位。核桃加工产业以核桃仁利用为主,而高附加值副产物如青皮、核桃壳及核桃仁种皮多丢弃或焚烧,不仅污染环境,还造成优质生物质资源浪费,核桃的应用价值仍有待进一步发掘。传统的核桃副产物加工技术或装置已经难以满足多领域对产量化和优质化要求,严重制约核桃产业的深度发展。因此,加大核桃副产物加工关键技术与装置的研发力度势在必行。对于青皮脱除,基于青皮结构和物理特性,刮削式、切割式、挤压式是脱皮装置的3种工作方式,分类总结了青皮脱除装置现状及其应用特点;不同类型装置的多因素性能试验可得到各自最优参数组合。对于关键过渡工序核桃干燥,核桃相应物理特性是设计干燥装置的重要依据,如含水率、孔隙率、导热系数及水分扩散率等,归纳了表征不同物理特性的参数值范围。分类阐述了热风、热泵、太阳能、气体射流及辐射干燥方式的工作机理及其应用;通过多因素性能试验,得到各类型装置性能的最优参数组合。对于核桃仁去种皮,基于核桃仁/种皮的理化特性,着重分析了碱液去皮和多种物理去皮方式;基于烘烤法提出了一种新型高温瞬时低损伤核桃仁去种皮的方法。对于核桃壳超微粉碎,基于核桃壳断裂界面特征,着重分类详述了多种粉碎机理;详述了创新型核桃壳超微粉碎装置以及核桃壳超微粉多粒径域分级装置。通过对核桃副产物加工4个关键环节对应的物理特性、工作机理、装置及其性能优化试验进行了系统总结和评述,期望加深对核桃副产物加工过程的理解,为提升核桃副产物加工水平提供理论依据与技术支持。

China’s walnut planting area and yield ranks first in the world,but the walnut processing industry mainly uses walnut kernel.High value-added by-products such as green husk,walnut shell,and walnut seed coat are discarded or incinerated,which not only pollute the environment but also cause waste of high-quality biomass resources.The application value of walnut remains to be further explored.Traditional walnut by-products processing technology or equipment is insufficient to meet the requirements of multi-field industry for walnut production and quality,seriously restricting the in-depth development of the walnut industry.Therefore,it is imperative to strengthen the research and development of key technologies and devices for preliminary processing of walnut fruit by-products.For green husk removal,three peeling principles of scraping,cutting,and extruding are analyzed based on the structural and physical characteristics.Based on the principles of peeling,the present situation and application characteristics of the peeling equipment are classified and summarized.The multi-factor performance tests of different types of devices are analyzed,and the optimal parameter combinations are obtained.For the drying of walnut in the key transition process,the corresponding physical characteristics of walnut,such as water content,porosity,thermal conductivity,and water diffusivity,are analyzed.The range of parameters representing different physical characteristics is obtained.The working mechanism and application of hot air,heat pump,solar energy,gas jet,and radiation drying modes are studied.Through multi-factors performance test,the main influencing factors and the optimal parameter combination of each type of device are obtained.Based on the physicochemical properties of walnut kernel/seed coat,this paper emphatically analyzed lye peeling and various physical peeling methods and put forward a new high temperature instantaneous low damage walnut seed coat peeling method based on the baking method.For walnut shell ultra-micro crushing,the fracture interface characteristics of the walnut shell are analyzed,the cracking and crushing mechanism are emphatically classified in detail,and a variety of innovative walnut shell ultra-micro crushing devices and walnut ultra-micro powder grading devices are introduced.This review systematically summarized the physical characteristics,working mechanism,device,and performance optimization test,corresponding to the key links of walnut by-product processing.The finding can be expected to deepen the understanding of walnut by-product processing and further provide theoretical basis and technical support for improving walnut processing level.