Macrowine 2021
IVES 9 IVES Conference Series 9 Kinetic study of browning caused by laccase activity using different substrates

Kinetic study of browning caused by laccase activity using different substrates

Abstract

AIM: To our knowledge all the studies about laccase kinetics and its inhibition have been performed with substrates and conditions very different from those of real grape juice. Moreover, none of these researches really measure enzymatic browning, since they have not taken into account what happens after the oxidation of o-diphenols in o-diquinones and their subsequent polymerization to form melanins1. For that reason, the aim of this research was to develop a new model to measure the kinetics of browning caused by Botrytis cinerea laccase under conditions much closer to those of grape juice and using the substrates naturally present in it.

METHODS: A grape juice model solution containing 100 g/L of D-glucose, 100 g/L of D-fructose and 4 g/L of tartaric acid adjusted to pH 3.5 was used for all the browning assays. Five phenolic compounds including one triphenol: gallic acid; three orthodiphenols: caftaric acid, (+)-catechin and (-)-epicatechin; and one monophenol: 4-hydroxybenzoic acid were used at concentrations between 0 and 0.8 mM. Laccase from Botrytis cinerea was purified according to Vignault et al., (2019)2. Browning reaction was started by adding 2 units of laccase activity/mL and absorbance at 420 nm was measured at time 0, 15, 30 and 45 minutes. The slope of the regression straight line was determined in order to express the intensity of browning. The Michaëlis-Menten and Hill plots were depicted for each substrate in order to determine the kinetic parameters of browning: Vmax, K0.5 and Hill number. All the experiments were performed in triplicate

RESULTS: The results indicate that o-diphenols are better substrates for laccase browning than triphenols and that monophenols, or at least 4-hydroxybenzoic acid, do not appear to be reactive. Moreover, of the o-diphenols, (+)-catechin showed the greatest browning intensity, followed in decreasing order by (-)-epicatechin and caftaric acid.

CONCLUSIONS: This research proposes a synthetic model for measuring laccase browning in a matrix close to real grape juice that makes it possible to study how laccase browning acts in the presence of different possible substrates. Further studies are needed to verify the efficiency of the proposed model on other laccase substrates such as anthocyanins, flavonols and proantocyanidins, and also to determine the inhibitory effect toward laccase browning of the most frequently used antioxidants – sulfur dioxide, ascorbic acid and glutathione – and other possible inhibitors of laccase browning such as oenological tannins.

FUNDING:

This work was funded by CICYT (Efecto de las lacasas sobre la sensorialidad, calidad y salubridad de los vinosproject RTI2018-095658-B-C33).

ACKNOWLEDGMENTS:

Authors thank professors Marc Fermaud and Jean Roudet from INRAE, UMR SAVE, Bordeaux Science Agro, ISVV, France for having provided us with the B. cinerea strain.

DOI:

Publication date: September 28, 2021

Issue: Macrowine 2021

Type: Article

Authors

Fernando Zamora, Pol Giménez, Sergi Anguela, Arnau Just-Borras, Pere Pons-Mercadé, Jordi Gombau, Adeline Vignault,  Joan Miquel Canals, Pierre-Louis Teissedre, Fernando Zamora

Departament de Bioquímica i Biotecnologia, Facultat d’Enologia de Tarragona, Universitat Rovira i Virgili, C/Marcel.li Domingo, 1. 43007 Tarragona, Spain.
Unité de Recherche Oenologie, EA 4577, USC 1366 INRAE, ISVV, Université de Bordeaux, F33882 Villenave d’Ornon, France. – 11 rue Aristide Bergès, 33270 Floirac, France,

Contact the author

Keywords

laccase, botrytis cinerea, browning, kinetics

Citation

Related articles…

Bioclimatic shifts and land use options for Viticulture in Portugal

Land use, plays a relevant role in the climatic system. It endows means for agriculture practices thus contributing to the food supply. Since climate and land are closely intertwined through multiple interface processes, climate change may lead to significant impacts in land use. In this study, 1-km observational gridded datasets are used to assess changes in the Köppen–Geiger and Worldwide Bioclimatic (WBCS)

Legacy of land-cover changes on soil erosion and microbiology in Burgundian vineyards

Soils in vineyards are recognized as complex agrosystems whose characteristics reflect complex interactions between natural factors (lithology, climate, slope, biodiversity) and human activities. To date, most of the unknown lies in an incomplete understanding of soil ecosystems, and specifically in the microbial biodiversity even though soil microbiota is involved in many key functions, such as nutrient cycling and carbon sequestration. Soil biological properties are indicative of soil quality. Therefore, understanding how soil communities are related to soil ecosystem functioning is becoming an essential issue for soil strategy conservation. Here, we propose to assess the importance of land-cover history on the present-day microbiological and physico-chemical properties. The studied area was selected in the Burgundian vineyards (Pernand-Vergelesses, Burgundy, France) where land occupation has been reconstructed over the last 40 years. Soil samples were collected in five areas reflecting various land cover history (forest, vineyards, shifting from forest to vineyards). For each area, physico-chemical parameters (pH, C, N, P, grain size) were measured and DNA was extracted to characterize the abundance and diversity of microbial communities. The obtained results show significant differences in the five areas suggesting that present-day microbial molecular biomass and bacterial taxonomic is partly inherited from past land occupation. Over longer period of time, such study of land-uses legacies may help to better assess ecosystem recovery and the impact of management practices for a better soil quality and vineyards sustainability.

Climate and the evolving mix of grape varieties in Australia’s wine regions

The purpose of this study is to examine the changing mix of winegrape varieties in Australia so as to address the question: In the light of key climate indicators and predictions of further climate change, how appropriate are the grape varieties currently planted in Australia’s wine regions? To achieve this, regions are classified into zones according to each region’s climate variables, particularly average growing season temperature (GST), leaving aside within-region variations in climates. Five different climatic classifications are reported. Using projections of GSTs for the mid- and late 21st century, the extent to which each region is projected to move from its current zone classification to a warmer one is reported. Also shown is the changing proportion of each of 21 key varieties grown in a GST zone considered to be optimal for premium winegrape production. Together these indicators strengthen earlier suggestions that the mix of varieties may be currently less than ideal in many Australian wine regions, and would become even less so in coming decades if that mix was not altered in the anticipation of climate change. That is, grape varieties in many (especially the warmest) regions will have to keep changing, or wineries will have to seek fruit from higher latitudes or elevations if they wish to retain their current mix of varieties and wine styles.

Exploring resilience and competitiveness of wine estates in Languedoc-Roussillon in the recent past: a multi-level perspective

The Languedoc-Roussillon wineries are facing a decline in wine yields particularly PGI yields due to many factors. Climate change is just ones, but is expected to increase in the future. There is also structurally a large heterogeneity of yield profiles among terroirs, varieties and strategies. This work investigates the link between yield, competitiveness and resilience to explore how resilient winegrowers have been in the recent past. To this end two approaches have been combined; (i) an accountancy database analysis at estate scale and (ii) municipality level competitiveness analysis. A new resilience indicator that characterizes the capacity of an estate to absorb yield variation is also defined. The FADN database between 2000 and 2018 of ex-Languedoc-Roussillon (France) and other data are used to analyse the current situation and the past evolution of competitiveness and resilience by type of estate (type of farm: PGI and/or PDO & type of commercialization: bulk and/or bottles). The net margin, which defines competitiveness, is not correlated to yield for all types but depends on the type of commercialization and the level of specialisation. The resilience indicator shows that the net margin of estates specialized in PGI is particularly sensitive to yield declines. We also show that price evolutions seem to compensate the effect of yield losses for the majority of types. Municipality scale analysis shows the links between local pedoclimate, yield, commercialization strategies and price. Overlapping a PDO with a PGI does not always increase a municipality’s PGI competitiveness. It is difficult to make links between causes and effects due to the complexity of the wine production system. Production diversification may be a solution. Resorting to the two level of analysis helps resolving the data gap that is necessary to explore the links between yield and economic performance of the wine estates in the long term.

Grapevine varietal diversity as mitigation tool for climate change: Agronomic and oenologic potential of 14 foreign varieties grown in Languedoc region (France)

Climate change effects in Languedoc include an expected rise in temperatures, increased evapotranspiration as well as more severe and frequent climatic hazards, such as frost, drought periods and heat waves. For winegrowers theses phenomena impact both yield and quality, resulting in more frequent unbalanced wines. Research on identified mitigation tools for vineyard management is necessary to improve resilience of grapevine agrosystems. Varietal assortment is one of them. This study focuses on agronomic and oenologic potential of 14 foreign varieties grown in Languedoc French region. Fourteen grapevine varieties were monitored during 2021 from June until harvest on eight different sites, some of which occurring on more than one site adding up to 21 different modalities: 7 white varieties Alvarinho B, Assyrtiko B (2), Malvasia Istriana B, Parellada B, Verdejo B, Verdelho B, Xarello B, and 7 black varieties Saperavi N (2), Touriga nacional N, Baga N, Aleatico N, Montepulciano N (2), Primitivo N (3), Calabrese N (3). Varietals were compared through the following parameters: phenology was assessed by using the information collected in the Database Network of French Vine Conservatories (INRAE-SupAgro-IFV, 2005-2015). The number of inflorescences for shoots from secondary buds and bourillons and suckers were observed to assess post-bud break frost tolerance potential. Grapevine water status was studied through stem water potential measurement, observation of foliage symptoms of drought, and 𝛿13C on must. Frequencies and intensities of downy mildew, powdery mildew, and black rot attacks were estimated before harvest on leaves and clusters and botrytis at harvest to assess disease susceptibilities. Berry composition was monitored from end of veraison until harvest. Yield and mean bunch weight were also calculated. Varieties were then ranked on a 1-4 scale for each parameter and compared through PCA. Forty two stations of the Mediterranean basin were compared by PCA with the Multicriteria Climatic Classification indicators in order to confront the collected information during 2021 campaign to the hypothesis that plants coming from dry and hot regions are genetically adapted to such climatic conditions.