Department of Analytical Chemistry & Research Institute on Water, Climate Change & Sustainability (IACYS), University of Extremadura, 06006, Badajoz, Spain.
LAQV/REQUIMTE, Laboratório de Química Aplicada, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal.
Sci Rep. 2020 Apr 10;10(1):6246. doi: 10.1038/s41598-020-63407-8.
Near infrared spectroscopy (NIRS) and mid-infrared spectroscopy (MIRS) in combination with chemometric analysis were applied to discriminate the geographical origin of grapevine leaves belonging to the variety "Touriga Nacional" during different vegetative stages. Leaves were collected from plants of two different wine regions in Portugal (Dão and Douro) over the grapes maturation period. A sampling plan was designed in order to obtain the most variability within the vineyards taking into account variables such as: solar exposition, land inclination, altitude and soil properties, essentially. Principal component analysis (PCA) was used to extract relevant information from the spectral data and presented visible cluster trends. Results, both with NIRS and MIRS, demonstrate that it is possible to discriminate between the two geographical origins with an outstanding accuracy. Spectral patterns of grapevine leaves show significant differences during grape maturation period, with a special emphasis between the months of June and September. Additionally, the quantification of total chlorophyll and total polyphenol content from leaves spectra was attempted by both techniques. For this purpose, partial least squares (PLS) regression was employed. PLS models based on NIRS and MIRS, both demonstrate a statistically significant correlation for the total chlorophyll (R = 0.92 and R = 0.76, respectively). However, the PLS model for the total polyphenols, may only be considered as a screening method, because significant prediction errors, independently of resourcing on NIRS, MIRS or both techniques simultaneously, were obtained.
近红外光谱（NIRS）和中红外光谱（MIRS）结合化学计量学分析被应用于区分不同生长阶段的“Touriga Nacional”葡萄品种的叶片的地理来源。叶片取自葡萄牙（Dão 和 Douro）两个不同葡萄酒产区的植株，跨越葡萄成熟时期。设计了一个采样方案，以便在考虑到太阳照射、土地倾斜度、海拔和土壤特性等变量的情况下，在葡萄园内部获得最大的可变性。主成分分析（PCA）用于从光谱数据中提取相关信息，并呈现出明显的聚类趋势。结果表明，无论是使用 NIRS 还是 MIRS，都可以出色地识别出两个地理来源。葡萄叶片的光谱模式在葡萄成熟期间表现出显著差异，特别是在 6 月和 9 月之间。此外，还尝试通过两种技术从叶片光谱中定量测定总叶绿素和总多酚含量。为此，采用了偏最小二乘（PLS）回归。基于 NIRS 和 MIRS 的 PLS 模型均表现出总叶绿素的统计学显著相关性（R = 0.92 和 R = 0.76）。然而，对于总多酚的 PLS 模型，只能被认为是一种筛选方法，因为获得了独立于 NIRS、MIRS 或同时使用两种技术的显著预测误差。
