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…

Delaying grapevine budbreak and/or phenological stages

In the current climatic context, with milder winters leading to earlier budburst in most wine regions, vines are exposed to the risk of spring frosts for a longer period. Depending on the year, frost can lead to yield losses of between 20 and 100 %, jeopardizing the economic survival of wine estates. In addition, by destroying young shoots, spring frosts can impact the following season’s production, by reducing the number of canes available for pruning, for example. Late pruning is one method to combat spring frosts.

Wine growing terroirs: management of potential. New issues at stake for AOCs in France

Terroirs represent a heritage that must be studied and managed with appropriate methods; recourse to agronomic and oenological sciences alone is necessary, but is in no way sufficient without the contribution of the humanities.

Microbial life in the grapevine: what can we expect from the leaf microbiome?

The above-ground parts of plants, which constitute the phyllosphere, have long been considered devoid of bacteria and fungi, at least in their internal tissues and microbial presence there was long considered a sign of disease. However, recent studies have shown that plants harbour complex bacterial communities, the so-called “microbiome”[1]. We are only beginning to unravel the origin of these bacterial plant inhabitants, their community structure and their roles, which in analogy to the gut microbiome, are likely to be of essential nature. Among their multifaceted metabolic possibilities, bacteria have been recently demonstrated to emit a wide range of volatile organic compounds (VOCs), which can greatly impact the growth and development of both the plant and its disease-causing agents.

Comparison between satellite and ground data with UAV-based information to analyse vineyard spatio-temporal variability

Currently, the greatest challenge for vine growers is to improve the yield and quality of grapes by minimizing costs and environmental impacts. This goal can be achieved through a better knowledge of vineyard spatial variability. Traditional platforms such as airborne, satellite and unmanned aerial vehicles (UAVs) solutions are useful investigation tools for vineyard site specific management.

Study of the volatile aroma profile of five Italian grape varieties submitted to controlled postharvest withering

Wines made with grapes submitted to postharvest dehydration are often referred to as “passito” or “straw wines.” This distinct style of winemaking consists of a process of water loss that allows the berries to undergo a mild water stress and senescence process [1].