Cell Walls Of Grape Mesocarp Possible Fining Agents For Red And White Wine

Abstract

Clarification or fining of wines is a technique used in wineries to eliminate unwanted wine components, which negatively affect its quality. Clarification normally involves the addition of an adsorptive material that eliminates or reduces the presence of undesirable components. The problem is that many of the fining agents used in the industry contain allergens, such as caseinates or ovalbumin. The possibility of using plant cell wall material as finning agent has been previously studied [1,2]. Other possible fining agent could be the plant cell walls material from the pulp of the grape. This material is generated during the crushing of the grape and it presence could be a problem during the maceration stage, since it greatly reduces, by adsorption, the concentration of phenolic compounds in the wine. However, due to its great affinity for tannins, it could be used to reduce the wine astringency.The objective of this study was to analyze the ability of freeze-dried grape pulp plant cell walls to act as a clarifying agent in red wines of three different varieties: Cabernet Sauvignon, Syrah and Monastrell, and one white wine of the Airén variety. 0.5 g of the lyophilized cell walls were put in contact and mixed with 50 mL of the corresponding wine (tests in triplicate), and a contact time of 7 days was assayed, after which their chromatic characteristics and total tannin concentration were analyzed by spectrophotometry. Their anthocyanin and tannin composition were also analyzed by HPLC. The material was also tested for their ability to reduce the concentration of ochratoxin A and histamine in wines.The results showed that the freeze-dried cell walls of the grape pulp have a high capacity of retaining phenolic compounds, especially tannins, although there were differences between the varieties. The treated Cabernet Sauvignon wine showed the greatest reduction in tannin concentration after finning (23%), followed by Monastrell wine (18.3%) and Syrah wine (14.3%).A problem with most fining agents is that they not only bind to tannins, but also to anthocyanins. In this way, the freeze-dried walls of grape pulp also reduced the concentration of anthocyanins in the three red variety wines, although to a lesser extent than with tannins. In this case, there were practically no differences in anthocyanin reduction between the studied wines, Monastrell (12.3%), Syrah (11.3%) and Cabernet sauvignon (12.5%).In all the wines, the addition of this fining agent reduced the concentration of ochratoxin A by 50%. However, it was not so powerful when removing histamine, where only a reduction of 8% was achieved in Monastrell and Cabernet Sauvignon wines.In conclusion, grape pulp cell walls could be a fining agent that competes with other commercial agents currently used. In addition, this plant material is generated during the vinification, so their reuse as fining agent would contribute to a circular economy. 

References

1. Jiménez-Martínez, M. D., Gómez-Plaza, E., Molero, N., & Bautista-Ortín, A. B. (2017). Fining of red wines with pomace cell wall material: effect on wine phenolic composition. Food and Bioprocess Technology, 10(8), 1531-1539.
2. Jiménez-Martínez, M. D., Bautista-Ortín, A. B., Gil-Muñoz, R., & Gómez-Plaza, E. (2019). Fining with purified grape pomace. Effect of dose, contact time and varietal origin on the final wine phenolic composition. Food chemistry, 271, 570-576.