太赫兹技术在农产品品质检测中的研究进展

农产品质量安全日益受到关注。由于传统检测方法存在耗时长、操作复杂、消耗大量溶剂、成本高等问题，因而迫切需要开发快速无损检测技术。在电磁波谱中位于微波和红外辐射之间的太赫兹波，因其所处波段的特殊性，使其具有了瞬态性、高穿透性、宽带性、相干性和低能性等一系列特性，太赫兹技术可以有效反映有机生物分子的结构和性质，作为物质“指纹”谱，该技术逐渐应用于有机生物分子的定性、定量分析，在近红外光谱、拉曼光谱、X射线等众多光谱类快速无损检测技术中成为一种极具竞争力的新兴检测技术。首先介绍了太赫兹波特点，太赫兹光谱及其成像技术原理；其次，在其基础上总结了太赫兹数据处理一般流程及其主要步骤中的常用分析方法，着重对定量、定性分析步骤中模型搭建方法、评估方法、评估指标进行了阐述；再次，讨论了近几年来太赫兹技术在农产品品质检测中的几个关键领域应用和研究进展，具体包括农药残留、抗生素、毒素等微量有害物质检测，掺假、转基因和外源异物的鉴别以及农产品内部营养成分含量预测等；最后，系统探讨了太赫兹技术在农产品品质检测领域尚需解决的问题，以此为导向总结需要进一步加强的研究方向，并对太赫兹技术在农产品品质领域未来发展作出展望。已有研究文献表明太赫兹技术在农产品品质检测领域的有效性。尤其，对非极性物质不敏感的特性，使其对已包装农产品的品质检测与评估具有得天独厚的优势。随着机器学习、强化学习等信息科学技术发展，一方面进一步加强太赫兹数据分析技术研究，通过数据自主学习，从数据角度揭示科学规律，构建精度更高、运算开销更小、实时性更强、泛化能力更好的分析模型；另一方面从分子振动理论出发，结合化学、物理学知识，研究太赫兹光谱特性的形成机理，并将获取的先验知识应用于分析模型的构建，通过数据与机理二者有机结合，提高太赫兹光谱分析软实力。未来硬件系统开发上以便携、低成本、灵敏度高为目标，最终实现太赫兹技术应用从实验室研究阶段逐渐走向商用工程化应用。

Progress in Terahertz Technique for Quality Inspection of Agro-Food Products

The safety and quality of agro-food has attracted increasing attentions. Due to the problems of traditional detection methods, such as being time-consuming, operation complicated, solvent-consuming and high-cost, it is essential to develop rapid and non-destructive detection methods. Terahertz(THz) ,which lies between the mid-infrared and microwave ranges, has unique properties such as transient, transmission, broadband, coherence and low-energy. THz wave can indicate structures and characteristics of many biomolecules, and be used in the quantitative and qualitative analysis of organic biomolecules as “fingerprint”. Therefore, compared with other spectroscopy techniques such as NIR, Raman and X-ray, THz has become an extremely competitive tool for agri-food products inspection. In this paper, the characteristics of THz wave and the principles of THz spectroscopy and imaging technique were introduced at first. Then THz data analysis process and the commonly used methods in its main steps were given, in which the quantitative and qualitative model construction and evaluation were emphatically introduced. Thirdly, the application and research progress of THz technique in the agro-food quality inspection which contains the detection of pesticide residues, antibiotic, toxins, identification of adulteration、transgenetic agro-food and foreign body, and prediction of the content of nutrient contents were discussed. Finally，the challenges that THz technique in the agro-food quality detection has to face were discussed systematically, based on which the research directions were pointed out, and the future outlook for THz technique was also discussed. The published literatures have indicated that THz technique is an effective solution in the agro-food quality inspection, especially THz wave can penetrate many commonly used nonpolar dielectric materials, which gives it superiorities in detection of packaged agro-food products. With the development of information technology, such as machine learning and intensive learning, on one hand, the THz data analysis technique needs to be strengthened. Through data self-learning, we can reveal the scientific rule from the data point of view, and build an analytical model with higher accuracy, lower computation cost, stronger real-time performance and better generalization ability. On the other hand, based on molecular vibration theory and combined with knowledge of chemistry and Physics, the mechanism of the terahertz spectroscopic characteristics is studied, which can be used in the model construction. Thereby through the combination of these two sides, the soft power of the terahertz will be improved. Meanwhile developing cost-effective and portable THz spectrometer with high sensitivity is a future research trend. It is expected that the application of terahertz technique will gradually begin from the laboratory state to the engineer application.