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Towards on-line monitoring of phenolic content in red wine grapes: A feasibility study
Jose Luis Aleixandre-Tudo1, Helene Nieuwoudt2, Wessel du Toit3
1Department of Viticulture and Oenology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa; Departamento de Tecnologia de Alimentos, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain.
Abstract:
Spectroscopy techniques to efficiently measure phenolic composition in grape berries may be a suitable analytical practice, provided that robust calibrations are established. A contactless FT-NIR instrument was used for on-line spectral data collection from grapes transported on a conveyor belt system. Spectral data was also collected on static samples using the same NIR instrument. Spectral measurements of crushed berries captured from the conveyor belt system and the use of the homogenate extraction protocol as reference method provided the most accurate prediction models. Values obtained for errors in prediction (RMSEP%) and RPD were 12% and 2.37, 12.3% and 3.37, 7.8% and 3.2, 16.7% and 2.84 for tannins (mg/g) and anthocyanins (mg/g) on a fresh weight basis, total phenols and colour density (AU), respectively. The results observed in this study show the ability of NIR spectroscopy to monitor the phenolic composition of grape berries transported on a conveyor belt system online.
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