OENO IVAS 2019 banner
IVES 9 IVES Conference Series 9 OENO IVAS 9 OENO IVAS 2019 9 Chemical and Biochemical reactions, including grape and wines microorganisms impact 9 NMR approach for monitoring the photo-degradation of riboflavin and methionine

NMR approach for monitoring the photo-degradation of riboflavin and methionine

Abstract

The light exposure of white wine is responsible for several reactions leading to changes on colour, flavours and, consequently, affecting the sensory profile. These reactions can take place when the white wine is bottled in clear glass and their mechanisms are dependent on both light exposure and chemical composition of white wine. Particular attention has been given to the reaction involving riboflavin (RF), a photo-sensitizer compound, and methionine (Met), a sulfur-containing amino acid, that can cause the formation of volatile sulphur compounds (VSCs), namely methanethiol and dimethyl disulfide. These compounds are responsible for a defect known as light-struck taste. Previous studies showed that hydrolysable tannins, in particular those from nut galls, limited both the degradation of Met and the formation of VSCs. The effectiveness of hydrolysable tannins was also proved after light exposure and storage for 24 months.

 In order to better understand the role of tannins in the photo-degradative reactions, an NMR approach was carried out. A solution containing RF (0.2 mM) and Met (2 mM) acidified at pH 3.2 was exposed to light by using fluorescence light bulbs. The solution was exposed to light up to two hours sampling it every 15 minutes. The same experimental conditions were applied in presence of gallic acid (2 mM), a constitutive unit of nut gall tannins.

 The degradation of RF and Met was monitored and, as expected, their signals decreased as the light exposure increased. Results provided evidence that a new signal appeared at 2.64 ppm. This signal was assigned to the SOCH3 moiety of methionine sulfoxide through the addition of the standard solution and standard 2D-NMR assignment techniques. The formation kinetic of methionine sulfoxide was measured for increased duration of light exposure and its rate resulted two-folds lower with the addition of gallic acid. This result suggests that the limited degradation of Met in presence of tannins, also observed in previous studies, is due to their action as competitor with Met in reducing RF from its excited form.

 The NMR technique was suitable for monitoring the photo-degradative reaction of RF and Met. Further researches have been carried out in order to verify and prove the ability of tannins in quenching both singlet oxygen and RF.

DOI:

Publication date: June 11, 2020

Issue: OENO IVAS 2019

Type: Article

Authors

Daniela Fracassetti, Melissa Mastro, Sara Limbo, Antonio Tirelli, Enzio Ragg

Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano Via G. Celoria, 2 20133 Milan (Italy)

Contact the author

Keywords

Light exposure, Nuclear Magnetic Resonance, Oxidation, Tannins 

Tags

IVES Conference Series | OENO IVAS 2019

Citation

Related articles…

Des enjeux individuels à l’action collective

With the Federation of Wine Syndicates of Anjou and the Wine Syndicate of Angevin for direct sale to the Property, the Higher School of Agriculture of Angers was led to carry out, in 1995, a survey of winegrowers in Maine and Loire, with a view to grouping the supply of some of the wines intended for direct sale (Huet, 1995).

Grapevine adaptation to drought and resistance to Neofusicoccum parvum, causal agent of Botryosphaeria dieback

The sustainability of viticulture in response to climate change has been addressed mainly considering agronomic impacts, such as water management and diseases, either separately or together.
In grapevines, there is strong evidence that different genotypes respond differently to biotic and abiotic stresses. A screening was conducted on various local cultivars in response to drought and Neofusicoum parvum infection aiming to evaluate their susceptibility to abiotic stress and resistance to fungal diseases.

Dual mode of action of grape cane extracts against Botrytis cinerea

Crude extracts of Vitis vinifera canes represent a natural source of stilbene compounds with well characterized antifungals properties. In our trials, exogenous application of a stilbene extract (SE) obtained from grape canes on grapevine leaves reduces the necrotic lesions caused by Botrytis cinerea

Identification of arbuscular mycorrhizal fungi species preferentially associated with grapevine roots inoculated with commercial bioinoculants 

Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with plant roots and can help plants acquire nutrients from the soil in exchange for photosynthetic carbon. Commercial bioinoculants containing AMF are widely available and represent a potential opportunity to reduce the dependence of grapevines on agrochemicals. However, which commercially available AMF species colonize vine roots and affect vine growth remains unknown. The aim of this study was to identify the AMF species from commercial bioinoculants that colonize grapevine roots using high-throughput sequencing, and to evaluate the performance of five commercial bioinoculants and their effects on own-rooted Cabernet sauvignon.

Oenotannins addition in wine: can be the modulation of redox potential predictable?

The purpose of this research was to study the interaction between oenotannins and wine matrix in order to design a targeted oenotannins addition for modulating the redox status of wine. It is in fact known that oenotannins can regulate the redox potential of musts and wines since they are electroactive substances (1).