Kasampalis Dimitrios S, Tsouvaltzis Pavlos I, Siomos Anastasios S
Department of Horticulture, Aristotle University, 54124 Thessaloniki, Greece.
Horticultural Sciences Department, Southwest Florida Research and Education Center, University of Florida, Immokalee, FL 34142, USA.
Sensors (Basel). 2024 Nov 26;24(23):7547. doi: 10.3390/s24237547.
The market demand for baby leaf lettuce is constantly increasing, while safety has become one of the most important traits in determining consumer preference driven by human health hazards concerns. In this study, the performance of visible and near-infrared (vis/NIR) spectroscopy was tested in discriminating pesticide-free against pesticide-treated lettuce plants. Two commercial fungicides (mancozeb and fosetyl-al) and two insecticides (deltamethrin and imidacloprid) were applied as spray solutions at the recommended rates on baby leaf lettuce plants. Untreated-control plants were sprayed with water. Reflectance data in the wavelength range 400-2500 nm were captured on leaf samples until harvest on the 10th day upon pesticide application, as well as after 4 and 8 days during post-harvest storage at 5 °C. In addition, biochemical components in leaf tissue were also determined during storage, such as antioxidant enzymes' activities (peroxidase [POD], catalase [CAT], and ascorbate peroxidase [APX]), along with malondialdehyde [MDA] and hydrogen peroxide [HO] content. Partial least square discriminant analysis (PLSDA) combined with feature-selection techniques was implemented, in order to classify baby lettuce tissue into pesticide-free or pesticide-treated ones. The genetic algorithm (GA) and the variable importance in projection (VIP) scores identified eleven distinct regions and nine specific wavelengths that exhibited the most significant effect in the detection models, with most of them in the near-infrared region of the electromagnetic spectrum. According to the results, the classification accuracy of discriminating pesticide-treated against non-treated lettuce leaves ranged from 94% to 99% in both pre-harvest and post-harvest periods. Although there were no significant differences in enzyme activities or HO, the MDA content in pesticide-treated tissue was greater than in untreated ones, implying that the chemical spray application probably induced a stress response in the plant that was disclosed with the reflected energy. In conclusion, vis/NIR spectroscopy appears as a promising, reliable, rapid, and non-destructive tool in distinguishing pesticide-free from pesticide-treated lettuce products.
市场对婴儿叶生菜的需求不断增加，而安全性已成为受人类健康危害担忧驱动的决定消费者偏好的最重要特征之一。在本研究中，测试了可见和近红外（vis/NIR）光谱在区分未使用农药与使用农药处理的生菜植株方面的性能。两种商业杀菌剂（代森锰锌和乙磷铝）和两种杀虫剂（溴氰菊酯和吡虫啉）以推荐剂量作为喷雾溶液施用于婴儿叶生菜植株上。未处理的对照植株喷水。在施药后第10天收获前，以及在5℃下收获后储存4天和8天时，采集叶片样品在400 - 2500nm波长范围内的反射率数据。此外，在储存期间还测定了叶片组织中的生化成分，如抗氧化酶活性（过氧化物酶[POD]、过氧化氢酶[CAT]和抗坏血酸过氧化物酶[APX]），以及丙二醛[MDA]和过氧化氢[HO]含量。实施了偏最小二乘判别分析（PLSDA）并结合特征选择技术，以便将婴儿生菜组织分类为未使用农药或使用农药处理的组织。遗传算法（GA）和投影变量重要性（VIP）得分确定了11个不同区域和9个特定波长，这些区域和波长在检测模型中表现出最显著的效果，其中大部分位于电磁光谱的近红外区域。结果表明，在收获前和收获后时期，区分使用农药处理与未处理的生菜叶的分类准确率在94%至99%之间。虽然酶活性或HO没有显著差异，但使用农药处理的组织中的MDA含量高于未处理的组织，这意味着化学喷雾处理可能在植物中诱导了一种应激反应，这种反应通过反射能量得以揭示。总之，vis/NIR光谱似乎是一种有前途、可靠、快速且无损的工具，可用于区分未使用农药与使用农药处理的生菜产品。
