An electronic nose is an arrayed gas sensor mimicking the human olfactory system that can analyze and identify a flavour on collecting an odour from an environment. In our experiments, an electronic-nose system based on a surface acoustic wave (SAW) was used to measure the freshness of kiwifruit. 128° YX-LiNbO3 acted as a piezoelectric material; Au was deposited as an electrode and sensing area. With a polymer coating of various types on the sensing area and a connection to an oscillator circuit, a 113-114 MHz SAW was obtained. Depending on the properties of varied polymers, the frequency shift varied due to absorbed volatile organic compounds (VOC). In this way, with four surface-acoustic-wave sensors coated with varied polymers we built a kiwi-flavour database according to results from a TD-GC-MS system. When the concentration of esters increased, the kiwifruit began to ripen, accompanied by increased concentrations and types of VOC. As a result, polystyrene (PS) and fluoropolymer (CYTOP) polymers, which played the role of sensing materials, served as major materials to determine the ester aroma profile. Polyvinyl alcohol (PVA), polyvinyl butyral (PVB) and poly-N-vinylpyrrolidone (PNVP) were used to trap the alcohols and acids during a kiwifruit ripening period. This research proved that discrimination of differences is feasible from an unripe stage to a ripe stage and from a ripe stage to an over-ripe stage.

中文翻译：

---

基于表面声波技术的 TD-GC-MS 和气敏阵列检测猕猴桃新鲜度


电子鼻是模仿人类嗅觉系统的阵列气体传感器，可以从环境中收集气味来分析和识别味道。在我们的实验中，使用基于表面声波（SAW）的电子鼻系统来测量猕猴桃的新鲜度。 128°YX-LiNbO3作为压电材料；沉积金作为电极和传感区域。通过在传感区域上涂上各种类型的聚合物涂层并连接到振荡器电路，获得了 113-114 MHz SAW。根据不同聚合物的特性，吸收的挥发性有机化合物 (VOC) 会导致频移发生变化。这样，我们利用四个涂有不同聚合物的表面声波传感器，根据 TD-GC-MS 系统的结果建立了猕猴桃风味数据库。当酯类浓度增加时，猕猴桃开始成熟，伴随着VOC浓度和类型的增加。因此，起到传感材料作用的聚苯乙烯（PS）和含氟聚合物（CYTOP）聚合物成为确定酯香气特征的主要材料。在猕猴桃成熟期间，使用聚乙烯醇（PVA）、聚乙烯醇缩丁醛（PVB）和聚N-乙烯基吡咯烷酮（PNVP）来捕获醇和酸。本研究证明，从未成熟阶段到成熟阶段、从成熟阶段到过熟阶段差异判别是可行的。