Methyl jasmonate versus nano-methyl jasmonate. Effect on the tannin composition of monastrell grapes and wines

Abstract

Tannins are very important for grape and wine quality, since they participate in several organoleptic wine characteristics such as astringency perception, bitterness, and the colour stability. The compositions in tannins in grapes and wines differs between seeds and skins. Tannin seeds contain a higher concentration of tannins than skin and has been associated with a coarse and more tannic notes in wines, by contrast, tannin skin are related to a greater softness in the wines.

Several strategies can be used to improve the tannin composition in grapes and one of them could be the use of elicitors such as methyl jasmonate. The use of this elicitor has been proven to be efficient in the production of secondary metabolites which increases the quality of wines, but its use also has some drawbacks such as its low water solubility, high volatility, and its expensive cost (Gil-Muñoz et al. 2021).

This study observes the impact on tannin composition of must and wine of Monastrell grapes that have been treated with methyl jasmonate (MeJ) and methyl jasmonate n-doped calcium phosphate nanoparticles (nano-MeJ). The first objective of this study was to compare the effect of these treatments to determine if the tannin composition of the berries and wines increased. The second aim was to determine if the nanoparticle treatments showed similar effects to way treatments so that the ones which are more efficient and sustainable from an agricultural point of view can be selected. 

The experiments were conducted in a randomized block design during three consecutive seasons (2019-2021), in two foliar treatments were applied to the plants in spray form as a water suspension of MeJ (10 mM) and nano-MeJ (1 mM) at veraison. Control plants were sprayed with aqueous solution of Tween 80 alone. Tannins were analysed according to the methodology shown in Gil-Muñoz et al. (2018).

The results showed an increase in the values of total tannins in grapes for treatments except for nano-MeJ in the last year, although these were not statistically significant. Regarding wines, a greater increase was only obtained for treatments in 2019, in the other two seasons, this increase was only evident for MeJ. With respect to the epigallocatechin content was higher in nano-MeJ treated grapes in 2019 and 2020. Finally, this compounds was increased in wines from both treated grapes in 2019 and 2021, but only for in wines from MeJ treated grapes in 2020.