Macrowine 2021
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

Contact the author

Keywords

extraction, phenolic assay, red grapes, tannins

Citation

Related articles…

Reconstructing ancient microbial fermentation genomes from the wine residues of Herod, Roman king of Judea

The fortress of the Herodium, built towards the end of the first century BCE/ante Cristo, on the orders of Herod the Great, Roman client king of Judea, attests the expansion of Roman influence in the eastern Mediterranean. During archaeological excavations of the Herodium in 2017[1], a winery was discovered on the ground floor of the palace, with an assortment of clay vessels in situ, including large dolia – clay fermentation vessels each capable of fermenting up to 300-400 L of wine. Thanks to the recent progresses in the field of paleogenomics[2], we could analyse the organic material consistent with grape pomace at the bottom of these vessels, by extracting and sequencing the DNA using shotgun metagenomics and targeted capture, aiming for enrichment of DNA from fermentation associated microbes.

Evaluation of the site index model for viticultural zoning

Une variable composite, dénommée Indice de Site (SI), intégrant les propriétés physiques du sol et le mésoclimat, avait été proposée pour caractériser les terroirs dans le cadre d’une étude des vignobles de Cabernet Sauvignon de Hawke’s Bay en Nouvelle Zélande.

Pests and biodiversity management on a climate change scenario: A practical case

The weather anomalies comparing the 1971-2000 time frame and the last years has showned a dramatic scenario when, in some months, average temperature in above 3ºC and the reduction in precipitation in more than 30%.

Environmental and viticultural practice effects on the phenolic composition of grapes: impact on wine sensory properties

Grape phenolic compounds are located in the internal layers of grape skins and seeds. They are synthesized via the phenyl-propanoid biosynthetic pathway which is modulated by both biotic and abiotic factors.

Vineyard soils and landscapes of the Burgundy Côte (France): a historical construction worth preserving

The construction of vineyard landscapes along the Burgundy Côte is the result of geological processes and of human labour. Substratum diversity in this vineyard is the result of a very long history explained by the diversity of Jurassic sedimentary facies and Tertiary tectonic activity. The nature and thickness of Quaternary deposits (Weichselian scree debris and alluvial fans) reflect sediment dynamics concurrent with the last glaciation.