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…

Physical-chemical characterization of Moscatel de Setúbal fortified wines from different vintages

Moscatel de Setúbal is a Portuguese fortified wine with Protected Designation of Origin (PDO Setúbal), made from Moscatel de Setúbal grape variety (Muscat of Alexandria) [1].

Hanseniaspora in wine-making: their genetic modification and potential role in acid modulation

Hanseniaspora spp. are one of the most common yeast isolates in vineyards and wineries and play an important role in wine-making.

Climate projections over France wine-growing region and its potential impact on phenology

Climate change represents a major challenge for the French wine industry. Climatic conditions in French vineyards have already changed and will continue to evolve. One of the notable effects on grapevine is the advancing growing season. The aim of this study is to characterise the evolution of agroclimatic indicators (Huglin index, number of hot days, mean temperature, cumulative rainfall and number of rainy days during the growing season) at French wine-growing regions scale between 1980 and 2019 using gridded data (8 km resolution, SAFRAN) and for the middle of the 21th century (2046-2065) with 21 GCMs statistically debiased and downscaled at 8 km. A set of three phenological models were used to simulate the budburst (BRIN, Smoothed-Utah), flowering, veraison and theoretical maturity (GFV and GSR) stages for two grape varieties (Chardonnay and Cabernet-Sauvignon) over the whole period studied. All the French wine-growing regions show an increase in both temperatures during the growing season and Huglin index. This increase is accompanied by an advance in the simulated flowering (+3 to +9 days), veraison (+6 to +13 days) and theoretical maturity (+6 to +16 days) stages, which are more noticeable in the north-eastern part of France. The climate projections unanimously show, for all the GCMs considered, a clear increase in the Huglin index (+662 to 771 °C.days compared to the 1980-1999 period) and in the number of hot days (+5.6 to 22.6 days) in all the wine regions studied. Regarding rainfall, the expected evolution remains very uncertain due to the heterogeneity of the climates simulated by the 21 models. Only 4 regions out of 21 have a significant decrease in the number of rainy days during the growing season. The two budburst models show a strong divergence in the evolution of this stage with an average difference of 18 days between the two models on all grapevine regions. The theoretical maturity is the most impacted stage with a potential advance between 40 and 23 days according to wine-growing regions.

Breeding grapevines for disease and low temperature tolerance: the U.S. perspective

Most grape scion cultivars grown around the world are derived from a single species, Vitis vinifera. Yet, the proportion of interspecific hybrids is increasing for a variety of reasons, including resistance to abiotic stresses such as low temperatures; societal, economic and environmental pressures to reduce pesticide usage; and to add a greater range of flavors to new table grape cultivars.

Delayed irrigation nearly doubles yield loss compared to anthocyanin gain in Southern Oregon Pinot noir

Irrigation initiation timing is a critical annual management decision that has cascading effects on grapevine productivity and wine quality.