LAQV/REQUIMTE, Laboratório de Química Aplicada, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, Porto 4050-313, Portugal.
CVRVV, Comissão de Viticultura da Região dos Vinhos Verdes, Rua da Restauração, 318, Porto 4050-501, Portugal.
Talanta. 2018 Aug 15;186:306-314. doi: 10.1016/j.talanta.2018.04.075. Epub 2018 Apr 25.
Routine wine analysis are commonly employed to ensure the quality and safety standards, and to meet consumers' demands and legal requirements. In the last decades, efforts have been done in order to replace the traditional analytical techniques by vibrational spectroscopic techniques such as near infrared (NIR) and mid infrared (MIR) spectroscopy. The potential of these techniques has already been proved by several studies that revealed their ability for the determination of several wine parameters with high levels of precision and accuracy. Raman spectroscopy, (which is also a vibrational technique), was much less explored in the wine industry. In this work, the ability of Raman spectroscopy for routine wine analysis was evaluated and compared to NIR and MIR spectroscopy. Several calibration models were developed aiming the quantitative assessment of alcoholic strength, density, total acidity, volatile acidity, total sugars and pH in white wines. For this purpose, partial least squares (PLS) regression was employed, enabling the correlation between reference results and spectral information obtained by NIR, MIR and Raman spectroscopy. Results revealed the better performance of MIR spectroscopy for the measurement of alcoholic strength (R = 0.99, RMSEP=1.77%, and RER=56.41), and total acidity (R = 0.98, RMSEP=2.02%, and RER=49.46). Raman spectroscopy was pointed out as the most suitable for the determination of total sugars (R = 0.97, RMSEP=5.12%, RER=19.52), and pH (R = 0.90, RMSEP=4.92%, RER=20.34). The three techniques presented similar results in what referred the assessment of density (R = 0.96, 0.98, and 0.97, RMSEP=4.72%, 3.90%, and 3.80%, for Raman, MIR, and NIR respectively). None of the three techniques seemed to be suitable for the accurate determination of volatile acidity (R <0.78, RMSEP>14.32%, and RER<6.98).
常规的葡萄酒分析通常用于确保质量和安全标准，满足消费者的需求和法律要求。在过去的几十年中，人们努力用振动光谱技术（如近红外（NIR）和中红外（MIR）光谱）来替代传统的分析技术。这些技术的潜力已经被几项研究证明，这些研究显示了它们在高精度和高准确性地测定葡萄酒参数方面的能力。拉曼光谱（也是一种振动技术）在葡萄酒行业的应用研究则较少。在这项工作中，评估了拉曼光谱在常规葡萄酒分析中的能力，并与 NIR 和 MIR 光谱进行了比较。为了定量评估白葡萄酒的酒精度、密度、总酸、挥发酸、总糖和 pH 值，建立了几个校准模型。为此，采用偏最小二乘法（PLS）回归，使参考结果与 NIR、MIR 和拉曼光谱获得的光谱信息相关联。结果表明，MIR 光谱在测量酒精度（R = 0.99，RMSEP = 1.77%，RER = 56.41）和总酸度（R = 0.98，RMSEP = 2.02%，RER = 49.46）方面表现更好。拉曼光谱被认为是测定总糖（R = 0.97，RMSEP = 5.12%，RER = 19.52）和 pH 值（R = 0.90，RMSEP = 4.92%，RER = 20.34）最适合的方法。在评估密度方面（R = 0.96、0.98 和 0.97，RMSEP = 4.72%、3.90% 和 3.80%，分别对应拉曼、MIR 和 NIR），这三种技术的结果相似。这三种技术都似乎不适合准确测定挥发酸（R <0.78，RMSEP >14.32%，RER <6.98）。
