Impacts of added oenological tannins on red wine quality to counteract Botrytis infection in Merlot grapes

The contamination of grape berries by Botrytis cinerea can drastically damage wine quality, in particular causing colour degradation. In musts obtained from botrytised grapes, SO2 addition is the main means of avoiding oxidation damage due to laccases excreted by the pathogen. However, consumers are becoming increasingly reluctant to accept SO2 addition to wine. Oenological tannins are used for fining wines because of their colloidal properties, and for wine colour stabilisation due to their ability to condense with anthocyanins. They are also known for their antioxidant and antioxidasic properties. They were thus investigated in the present study for their potential as an alternative to SO2 against laccase oxidation. The impact of various types of oenological tannins on musts and wines was studied once added to musts obtained from the Merlot cultivar, comprising 20 % and 50 % botrytised grapes. Laccase activity, antioxidant capacity, composition of phenolic compounds, spectrophotometric and CIELAB colour parameters were assessed in the musts and wines. Sensory analyses were also performed on 3-month-old wines to evaluate the visual, olfactory and gustative consequences of tannin addition. At a 50 % botrytisation rate, the addition of any type of oenological tannins (at a concentration of 100 g/hL) had no effect on laccase activity and did not protect phenolic compounds. However, at the same concentration and at a 20 % botrytisation rate, proanthocyanidin tannins from grape skin were found to be the most promising tannins with simultaneous protective effects, such as an inhibitory effect on laccase enzymes, protection of colour from complete degradation and preservation of some procyanidin compounds. Oenological tannins are promising candidates for protecting wines from Botrytis damage and they induce a differential effect according to their origin and structure. They could be used to reduce the amount of SO2 that is added during vatting. More research is needed to confirm and better understand the mode of action of various tannins at levels lower than the 20 % botrytised rate tested in the present study

New insight about the functionality of oenological tannins; Main results of the working group on oenological tannins

This communication synthetize all the results obtained by the OIV working group on oenological tannins to the current date. The obtained results confirm that oenological tannins really exert a protection effect against grape juice and wine oxidation because they have antioxidant activity, they consume directly oxygen and they exert an inhibitory effect on the laccase activity. Moreover, oenological tannins also exert a copigmentation effect which can improve and protect de color of red wines

Further characterization of an unusual plant mollicutes species of uncertain taxonomic status

International audienc

Conversion of wheat straw to furfural and levulinic acid in a concentrated aqueous solution of betaine hydrochloride

International audienceGlycine betaine hydrochloride (BHC), a safe acid industrially produced from the largely available glycine betaine isolated from the manufacture of sugar from beet, was used in combination with water to produce sustainable reaction media capable of selectively converting agricultural wastes to furfural and levulinic acid. At the end of the process, BHC can be conveniently recovered and recycled. Under optimized conditions, furfural was produced with 65% and 73% yield from wheat straw and xylan originated from beechwood, respectively. More importantly, by closely controlling the reaction temperature, it was possible to selectively drive the reaction either to xylose, furfural or levulinic acid. This process based on the use of biodegradable and safe BHC opens a sustainable route for the production of valuable fine chemicals from lignocellulosic biomass

Acholeplasma seiffertii sp. nov., a mollicute from plant surfaces

International audienc

Recent advances of the OIV working group on oenological tannins in the study of the functionalities of oenological tannins

This communication actualizes the status of the research of the OIV working group on oenological tannins with the purpose of deepening the knowledge of the mechanisms and functionalities of oenological tannins in winemaking. The obtained results confirm that oenological tannins really exert an effect as copigments and that they really protect the wine color against the negative effect of the enzyme laccase present in grapes affected by the infection of Botrytis cinerea

Influence of two prefermentative treatments to reduce the ethanol content and pH of red wines obtained from overripe grapes

This study researches treatments for reducing the ethanol content and pH of wine, by either adding or replacing a portion of overripe red grape juice with acidified water or with a white grape juice of low potential ethanol content previously treated with cationic exchange. All treatments resulted in wines with lower ethanol content; however, the treatments did not always correct wine acidity effectively and sometimes the wine composition was negatively affected because the other wine components were diluted. Specifically, both adding and substituting with acidified water caused an increase in wine pH and a general dilution of the other wine components, particularly when the water was added. In contrast, adding acidified must, unlike acidified water, significantly reduced wine pH and the dilution effect was lower, especially when a portion of the original must was replaced by a low sugar content white must treated by cationic exchange. Moreover, this practice is not unauthorized and seems not to affect, but rather improve, the sensory quality of the wine

New insight about the functionality of oenological tannins; Main results of the working group on oenological tannins

This communication synthetize all the results obtained by the OIV working group on oenological tannins to the current date. The obtained results confirm that oenological tannins really exert a protection effect against grape juice and wine oxidation because they have antioxidant activity, they consume directly oxygen and they exert an inhibitory effect on the laccase activity. Moreover, oenological tannins also exert a copigmentation effect which can improve and protect de color of red wines