Musingarabwi Davirai M, Nieuwoudt Hélène H, Young Philip R, Eyéghè-Bickong Hans A, Vivier Melané A
Institute for Wine Biotechnology, Department Viticulture and Oenology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
Institute for Wine Biotechnology, Department Viticulture and Oenology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
Food Chem. 2016 Jan 1;190:253-262. doi: 10.1016/j.foodchem.2015.05.080. Epub 2015 May 18.
Fourier transform (FT) near-infrared (NIR) and attenuated total reflection (ATR) FT mid-infrared (MIR) spectroscopy were used to qualitatively and quantitatively analyse Vitis vinifera L. cv Sauvignon blanc grape berries. FT-NIR and ATR FT-MIR spectroscopy, coupled with spectral preprocessing and multivariate data analysis (MVDA), provided reliable methods to qualitatively assess berry samples at five distinct developmental stages: green, pre-véraison, véraison, post-véraison and ripe (harvest), without any prior metabolite extraction. Compared to NIR spectra, MIR spectra provided more reliable discrimination between the berry samples from the different developmental stages. Interestingly, ATR FT-MIR spectra from fresh homogenized berry samples proved more discriminatory than spectra from frozen homogenized berry samples. Different developmental stages were discriminated by principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). In order to generate partial least squares (PLS) models from the MIR/NIR spectral datasets; the major sugars (glucose and fructose) and organic acids (malic acid, succinic acid and tartaric acid) were separated and quantified by high performance liquid chromatography (HPLC) and the data used as a reference dataset. PLS regression was used to develop calibration models to predict the concentration of the major sugars and organic acids in the berry samples from different developmental stages. Our data show that infrared (IR) spectroscopy could provide a rapid, reproducible and cost-effective alternative to the chromatographic analysis of the sugar and organic acid composition of grape berries at various developmental stages, using small sample volumes and requiring limited sample preparation. This provides scope and support for the possible development of hand-held devices to assess quality parameters in field-settings in real-time and non-destructively using IR technologies.
傅里叶变换（FT）近红外（NIR）光谱和衰减全反射（ATR）傅里叶变换中红外（MIR）光谱被用于对酿酒葡萄品种长相思葡萄浆果进行定性和定量分析。FT-NIR和ATR FT-MIR光谱，结合光谱预处理和多元数据分析（MVDA），提供了可靠的方法来定性评估处于五个不同发育阶段的浆果样品：绿色、转色前、转色期、转色后和成熟（收获）期，无需事先进行代谢物提取。与近红外光谱相比，中红外光谱能更可靠地区分不同发育阶段的浆果样品。有趣的是，新鲜匀浆浆果样品的ATR FT-MIR光谱比冷冻匀浆浆果样品的光谱更具区分性。通过主成分分析（PCA）和正交偏最小二乘判别分析（OPLS-DA）区分不同的发育阶段。为了从MIR/NIR光谱数据集中生成偏最小二乘（PLS）模型；主要糖类（葡萄糖和果糖）和有机酸（苹果酸、琥珀酸和酒石酸）通过高效液相色谱（HPLC）进行分离和定量，并将这些数据用作参考数据集。使用PLS回归建立校准模型，以预测不同发育阶段浆果样品中主要糖类和有机酸的浓度。我们的数据表明，红外（IR）光谱可以为葡萄浆果在不同发育阶段的糖和有机酸成分的色谱分析提供一种快速、可重复且经济高效的替代方法，使用的样品量小且样品制备要求有限。这为使用红外技术在田间实时、无损地评估质量参数的手持式设备的可能开发提供了空间和支持。
