Antonio MORATA, antonio.morata@upm.es (A.M.);
Carlos ESCOTT,  carlos.escott@upm.es (C.E.);
Iris LOIRA,  iris.loira@upm.es (I.L.);
MªAntonia BANUELOS, mantonia.banuelos@upm.es (M.A.B.);
Felipe PALOMERO,  felipe.palomero@upm.es (F.P.);
Carmen LOPEZ, carmen.lopez@upm.es (C.L);
Juan Manuel DEL FRESNO,juanmanuel.delfresno.florez@upm.es (J.M.Df.);
Cristian VAQUERO,c.vaquero@upm.es   (C.V.);
Elena ADELL & Karen GONZÁLEZ, carmen.gchamorro@upm.es (C.G.) 

enotecUPM. Chemistry and Food Technology Department, ETSIAAB, Universidad Politécnica de Madrid, Avenida Puerta de Hierro 2, 28040 Madrid, Spain; 

Campoviejo, Rioja, Spain; elena.adell@pernod-ricard.com (E.A.) 

Introduction 

Fumaric acid has been recently accepted by OIV as a regulated practice in enology. The application to inhibit malolactic fermentation (MLF) is highly effective. The control of undesired MLF is really interesting in the current scenario of global warming. Many times, roses, whites, and sparkling wines ongoing a MLF reducing the acidity and freshness producing flat wines that are also prone to microbial instabilities due to the high pH. The use of fumaric acid controls bacterial developments, inhibits MLF and produces wines with better acidity, lower pH and more stable. Moreover, it is possible to produce red wines without MLF that can be interesting to preserve acidity in wines from warm areas. This research shows for several varieties, wine types and vintages how the inhibition of MLF by fumaric acid produces wines with lower pHs and low volatile acidity. (Fig 1)[1]. 

Fig 1. Main impacts in enology of the use of Fumaric acid as inhibitor of malolactic fermentation [from reference 1. Creative Commons Attribution (CC BY) license].

Results and discussion

The MLFs performed for 3 years (2018, 2020 and 2021) with Tempranillo and Garnacha varieties were used for red wines, also Tempranillo for roses and Viura for white wines. In each case, four experiments were performed: Control under spontaneous MLF process; Control with inoculated MLF; Inhibition with FH2 during the spontaneous MLF process; and Inhibition with FH2 during an inoculated MLF. The addition of FH2 (600 mg/L) in most of the cases reduces the pH ≈ 0.1 units. The addition of FH2 inhibited the MLF preserving the malic acidity [2,3]. In absence of FH2 all the MLF were finished with residual malic acid contents below 0.05 g/L. When the MLF was inhibited by FH2, volatile acidity (VA) remained very low in the range 0.05–0.22 g/L. (Fig 2) [1]. 

Fig 2. Evolution of malic acid (black lines) and volatile acidity (red lines with circles) (g/L) in spontaneous or inoculated (alpha, O. oeni) MLFs with or without FH2 inhibition (600 mg/L) for trials performed in triplicate during 2021. Malic acid in control (short dashed black line), control with FA (dashed black line), control with LAB (continuous black line), and control with FA and LAB (dotted black line). Volatile acidity in control (short dashed red line), control with FA (dashed red line), control with LAB (continuous red line), and control with FA and LAB (dotted red line). Red wines from Tempranillo. [adapted from reference 1. Creative Commons Attribution (CC BY) license]

When the results of all trials (3 years, 3 varieties and 3 kind of wines) were represented as function of pH and VA, all the fermentations inhibited by FH2 were observed to remain at values close or lower than 0.2 g/L in volatile acidity and most of them below 3.6 in pH (Figure 4). Conversely the controls without FH2 remained close or higher than 0.2 g/L of volatile acidity, many of them showing values above 0.4. Concerning pH most of them were close or higher than 3.5, and many of them showing values above 3.7. 

Fig 3. Values of volatile acidity and pH in all trials (years 2018, 2020, and 2021) of controls inoculated or with spontaneous fermentation and treatments with MLF inhibited by FH2. [adapted from reference 1. Creative Commons Attribution (CC BY) license].

The acidity and freshness are well linked parameters [18] and deeply affected by MLF. MLF produces a typical deacidification in wines that easily increases pH in 0.1–0.2 units. The deacidification by MLF has been traditionally used to soften mouth perception of acidity in red wines, however, in the current scenario of global warming, many wines after MLF are excessively flat with pH values close to 4. Therefore, the inhibition of MLF by FH2 improves the sensory profile of these wines and helps to enhance the varietal aroma. 

Conclusions

This research developed under variable enological conditions, —wine composition (12.5 < %Ethanol < 14.4; 3.33 < pH < 3.67), grape variety (Tempranillo, Garnacha and Viura) and wine type (Red, Rose and white)—, shows that MLF can be controlled precisely and effectively by FH2.

  • Decrease of pH by FH2: 3.62 -> 3.50 (RW); 3.33 -> 3.25 (WW)
  • pH preservation without MLF: 3.77 -> 3.53 (RW); 3.49 -> 3.26 (WW)
  • Less volatile acidity: 0.45 -> 0.19 (RW); 0.28 -> 0.15 (WW)
  • Stable red wines without MLF
  • Powerful tool to improve freshness in warm areas
  • Better physicochemical and microbiological stability
  • Sparkling wines: control of undesired MLF during 2nd fermentation 
References
  1. Morata, A.; Adell, E.; López, C.; Palomero, F.; Suárez, E.; Pedrero, S.; Bañuelos, M.A.; González, C. Use of Fumaric Acid to Inhibit Malolactic Fermentation in Bottled Rioja Wines: Effect in pH and Volatile Acidity Control. Beverages 2023, 9, 16. https://doi.org/10.3390/beverages9010016

  2. Morata, A.; Bañuelos, M.A.; López, C.; Song, C.; Vejarano, R.; Loira, I.; Palomero, F.; Suarez Lepe, J.A. Use of fumaric acid to control pH and inhibit malolactic fermentation in wines. Food Addit. Contam. Part A 2020, 37, 228–238. https://doi.org/10.1080/19440049.2019.1684574

  3. Morata, A.; Bañuelos, M.A.; López, C.; Adell, E. Use of fumaric acid to control pH and inhibit malolactic fermentation in wines. In Proceedings of the Ives Science Meeting, Margaux-Cantenac, France, 16–17 June 2022.

  4. Morata, A.; Escott, C.; Bañuelos, M.A.; Loira, I.; del Fresno, J.M.; González, C.; Suárez-Lepe, J.A. Contribution of Non-Saccharomyces Yeasts to Wine Freshness. A Review. Biomolecules 2020, 10, 34. https://doi.org/10.3390/biom10010034