 IVES 9 IVES Conference Series 9 Development of a new commercial phenolic analysis method for red grapes

Development of a new commercial phenolic analysis method for red grapes

Abstract

Grape phenolic content is an important quality factor that influences the appearance and mouthfeel of premium red wines. The wine industry uses a variety of commercial phenolic assays to determine phenolic maturity in red grapes. Some of these assays, however, are dated more than 20 years ago and do not always accurately reflect wine phenolic content from grape phenolic extracts. The aim of this study is to develop an adjusted phenolic sample preparation and extraction protocol so it can be used in commercial wineries and/or laboratories.In this study, six grape cultivars (Pinotage, Cabernet-Sauvignon, Merlot, Shiraz, Cinsualt and Pertit Verdot) were collected from 42 different vineyards from across 15 different farms. Representative samples were taken from the grapes of each block. Grape extractions were done in duplicates using four different methods namely Glories, Iland, Modified Iland and a custom made Machine crushed method. The Glories, Iland and modified Iland methods produces homogenized grapes, while the machine crushed method uses grape samples where only the skins were crushed. The modified Iland and machine crushed extraction methods were exposed to microwave treatment and extracted in a 50% alcohol solution for 30 min and 1 hour and 3h, 24h and 40h, respectively.Wines were made from every grape samples. Phenolic analyses were done for anthocyanins, tannins, total phenols index and colour density on the grapes and wines. Variation in the phenolic composition of the grapes where the different extraction methods were observed. Correlations between grapes and wines phenolic data with the different grape extraction methods will also be shown.

DOI:

Publication date: September 7, 2021

Issue: Macrowine 2021

Type: Article

Authors

Asiphe Makalisa

South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University,Kiera Lambrecht, South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University Jose Luis Aleixandre Tudo, Universitat Politecnica de Valencia, Instituto de Ingenieria de Alimentos para el Desarrollo (IIAD), Departamento de Tecnología de Alimentos and Stellenbosch University, South African Grape and Wine Research Institute (SAGWRI), Department of Viticulture and Oenology Keren Bindon, Australian Grape and Wine Research Institute, Adelaide Wessel du Toit, South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University

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Keywords

extraction, phenolic assay, red grapes, tannins

Citation

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Local adaptation tools to ensure the viticultural sustainability in a changing climate

Mapping and tracking canopy size with VitiCanopy

Understanding vineyard variability to target management strategies, apply inputs efficiently and deliver consistent grape quality to the winery is essential. However, despite inherent vineyard variability, the majority are managed as if they are uniform. VitiCanopy is a simple, grower-friendly tool for precision/digital viticulture that allows users to collect and interpret objective spatial information about vineyard performance. After four years of field and market research, an upgraded VitiCanopy has been created to achieve a more streamlined, technology-assisted vine monitoring tool that provides users with a set of superior new features, which could significantly improve the way users monitor their grapevines. These new features include:
• New user interface
• User authentication
• Batch analysis of multiple images
• Ease the learning curve through enhanced help features
• Reporting via the creation of colour maps that will allow users to assess the spatial differences in canopies within a vineyard.
Use-case examples are presented to demonstrate the quantification and mapping of vineyard variability through objective canopy measurements, ground-truthing of remotely sensed measurements, monitoring of crop conditions, implementation of disease and water management decisions as well as creating a history of each site to forecast quality. This intelligent tool allows users to manage grapevines and make informed management choices to achieve the desired production targets and remain profitable.