Winemaking Update

WINEMAKING UPDATE

Number 1 – 2012

NEWS FLASH Sculpting the Aromatic Profile of ❖ The XXIIes Entretiens Scientifiques Lallemand technical meetings were a two- part event focused first on hot-climate red Wines through Diacetyl Management varietals and understanding their sensory development, and, second, on rosé n addition to carrying out the bio-dea- gly depend on the style and type of wine, winemaking and the impact of different cidification of wine, malolactic (ML) and varies from 0.2 mg/L for Chardonnay techniques on the wine style, including bacteria influence aroma and flavour wine, 0.9 mg/L for Pinot Noir, to 2.8 mg/L a presentation on the rosé wine market. I through various mechanisms, including the for Cabernet Sauvignon wine (Rankine et This year, the top scientists in the field presented on these topics to an interna- production of volatile grape- and yeast- al. 1969 and Martineau et al. 1995). When tional crowd, including winemakers from derived metabolites. In wine, one of those present at a high concentration (exceeding Eastern Europe. The event was also an volatile compounds – diacetyl – has impor- 5-7 mg/L), diacetyl is regarded by consumers opportunity to hand out the Lallemand tant stylistic implications. This diketone, to be undesirable in the wine, whereas at awards. The student award, the Prix also known as 2,3-butanedione, is associated around 1-4 mg/L, and depending on the style Michel-Feuillat – Entretiens Scientifiques with the “buttery” character of wine and and type of wine, it is considered to contri- Lallemand, was presented to Dr. Guillaume is formed as an intermediate metabolite in bute a desirable “buttery” or “butterscotch” Antalick, Université de Bordeaux II, for the reductive decarboxylation of pyruvic flavour character (Rankine et al. 1969 and his work on “Biochemical and sensory acid to 2,3-butanediol (figure 1). The for- Davis et al. 1985). changes associated with fruity notes in mation and degradation of diacetyl is closely red wines during malolactic fermentation. linked to the growth of such ML bacteria 2. Shaping the diacetyl content The importance of esters.” The Lallemand as Oenococcus oeni and the metabolism of in wine – Institute of Masters of Wine bursary was sugar, malic acid and citric acid. Yeasts are Several winemaking procedures can awarded to Sharon Wild, a second-year also able to synthesize diacetyl during alco- influence the diacetyl content in wine and, Master of Wine student from Australia for holic fermentation (AF). However, most therefore, influence the wine style desired. her essay responding to “Discuss the evo- of this diacetyl is further metabolized to Bartowsky and Henschke (2004) have pre- lution of rosé wine styles and consumer acetoin and 2,3-butanediol. This issue of sented the winemaking factors that affect preferences globally over the past five Winemaking Update will review winemaking diacetyl content. years.” Also on hand were the winners practices and the latest findings to help of the ML Wines competition (Madrid 2.1 The inoculation ratio of bacteria affects modulate diacetyl content in wine through 2011), who received their prizes from the the timing of induction and completion malolactic fermentation (MLF). president of Lallemand, Mr. Jean Chagnon. of MLF. It has been observed that a lower The proceedings of the 2011 Entretiens 1. Do I smell butter? inoculation ratio, such as 104-105 cfu/mL, Scientifiques are now available. can result in higher diacetyl accumulation in Diacetyl at low concentrations – and in wine, up to an eight-fold increase. combinations with other wine aroma compounds – will impart yeasty, nutty and toasty 2.2 The conversion of -acetolactate to WINEMAKING UPDATE aromas (Peynaud 1947 and Etievant 1991). diacetyl is a non-enzymatic decarboxylation At high concentrations, diacetyl has a cha- that is enhanced by the presence of oxygen. Winemaking update is published by racteristic buttery aroma associated with a A trial done by Nielson and Richelieu Lallemand to inform oenologists and wine- lactic character. The sensory threshold of (1999) showed that the amount of diacetyl making staff about the latest news and diacetyl in wine has been shown to stron- that accumulated in the wine varied greatly, applications arising from research. To request previous issues, or to send your questions or citric acid comments, contact us at: glucose citrate lyase acetic acid Lallemand Australia Pty Ltd aspartate aminotransferase Jason Amos oxaloacetic acid aspartic acid

23-25 Erudina Ave oxaloacetate CO2 decarboxylase pyruvate ATP Edwardstown, 5039, SA NAD NADH dehydrogenase acetate complex kinase Ph : +61 8 8276 1200 lactic acid pyruvic acid acetylphosphate acetic acid lactate dehydrogenase TTP [email protected] pyruvate decarboxylase CO2 The technical information in Winemaking acetaldehyde-TTP update is true and accurate at the time of α-acetolactate synthase publication. Due to the great diversity of α-acetolactic acid non-enzymatic decarboxylation CO2 winemaking operations, all information and α-acetolactate CO2 advice is provided with no guarantee or decarboxylase diacetyl reductase DIACETYL acetoin formal engagement. Lallemand products are NAD(P) NAD(P)H NAD(P)H widely available through distribution net- acetoin works. To find your local distributor, contact NAD(P) reductase us at the above address. 2,3- butanediol Figure 1. Pathway for citric acid metabolism by Oenococcus oeni. Eveline Bartowsky, adapted from Ramos et www.lallemandwine.com@ al. 1995. Continued with the formation of 2 mg/L under anaerobic metabolism in the must. In a study done on 16 conditions and 12 mg/L under semi-aerobic Chardonnay from Baden in Germany, we 14 12 conditions. compared diacetyl production from different 10 selected ML bacteria. We know that the 8 6 concentration is strain dependant in sequen- 4

2.3 Most strains of O. oeni are able to meta- tial inoculation (see section 3), but it does (mg/L) Diacetyl 2 0 bolize citric acid during MLF. The metabo- not appear that the citrate-negative charac- PN4 lism of citric acid is highly strain-dependant Beta VP41 teristic significantly lowered the level of dia- 49A1 Alpha Elios 1 relative to that of malic acid, and conse- no MLF

cetyl. Both citrate-negative strains behaved Lalvin 31 quently the depletion of citric acid in the similarly to strains VP41 and PN4, which Figure 2. Diacetyl concentration of Cabernet wine may not occur until after malic acid are citrate positive and considered low- and Sauvignon wines from Adelaide Hills, Australia, that depletion. Higher peak concentrations of medium-producers of diacetyl (figures avai- have undergone sequential malolactic fermentation with different selected malolactic bacteria. diacetyl generally correlate with an elevated lable upon request). concentration of citric acid. buttery or nutty styles that result when MLF 2.4 When MLF is conducted at lower tem- 5. Co-inoculation to reduce diacetyl content begins upon completion of AF. For example, peratures, such as 18°C rather than 25°C, it in figure 3, the Beta starter produces less tends to be slower, but the wines accumulate Co-inoculation of the wine with selected diacetyl in co-inoculation (48 hours) than in a higher concentration of diacetyl. yeast and ML bacteria also has important delayed inoculation (2/3 of AF) or sequential stylistic implications in terms of diacetyl 2.5 SO is able to interact with diacetyl in inoculation (post-AF). The impact of the ML 2 production. Whether or not to use co-inocu- a reversible manner. In the presence of SO , bacteria strain is not as strong in co-inocula- 2 lation for MLF is probably the most important diacetyl is reduced and the concentration of tion, as the wines will show repeatedly low decision during this step of winemaking. free diacetyl in the wine lowered. However, levels of diacetyl with this technique with as the SO2 content decreases, as for example Co-inoculation with yeast and ML bacteria different ML bacteria. during aging, the ratio of free diacetyl will (inoculation with the ML bacteria within increase again, thus increasing its sensory 24 hours after yeast inoculation), allows an 1.5 impact. acclimatization of the ML bacteria during AF and an early start of malic acid degradation 1 3. Choosing the right malolactic towards the end of or immediately after AF, 0.5 bacteria for sequential inoculation when yeast cells are still alive. Under these

Diacetyl (mg/L) Diacetyl 0 reductive conditions generated by active When MLF is desired, the ML bacteria appear CY3079-Beta CY3079-Beta CY3079-Beta to be an important control point to influence yeast cells, which consume part of the oxygen Co-inoculation Delayed Sequential the final diacetyl concentration. The forma- available, diacetyl is immediately reduced Figure 3. Diacetyl productioninoculation in Chardonnayinoculation 2010 tion and degradation of diacetyl are closely to acetoin then to 2,3-butandiol, which has (Val de Loire) with different timing of inoculation for linked to the growth of ML bacteria and the little sensory impact. malolactic fermentation metabolism of sugar, malic acid and citric In co-inoculation situations, we also have an 6. Some guidelines acid. Certain ML bacterial strains (table 1) earlier stabilization of the wines. Less citric have been observed to produce a higher resi- acid is then consumed and, consequently, The recommendations in table 2 summarize dual concentration of diacetyl in wines than diacetyl is also lower. Our studies show that the actions that can be undertaken to shape other strains, principally when sequential co-inoculation often results in more fruit- the diacetyl content of wines. inoculation is used for MLF. In a study done at driven wine styles as opposed to the lactic, the AWRI by Bartowsky (2010) on Cabernet Sauvignon wines in Southern Australia, the MT01 VP41 Elios 1 Alpha Lalvin31 PN4 Beta results show that some ML bacteria will pro- Standard Very late attack of Late attack Medium Medium Early Very early attack duce significantly different concentrations of build-up citric acid - Only of citric attack of attack of attack of of citric acid diacetyl during sequential inoculation (figure culture attacks citric acid acid, at the citric acid citric acid citric acid (beginning/mid- after completion end of MLF during during (mid MLF) MLF) 2). It was also found that the later O. oeni use No of malic acid MLF MLF citric acid during MLF, the less diacetyl they production Low Medium High production produce (table 1). of diacetyl Very low production Medium Medium production of diacetyl production of of diacetyl production production of diacetyl in sequential 4. How important is the ability to diacetyl of diacetyl of diacetyl inoculation use citric acid? Table 1. Impact of different malolactic bacteria on the production of diacetyl Some ML bacteria strains are called “citrate negative” and were thought to remove any Buttery aroma Fruit driven-style possibility of diacetyl production, as diacetyl Sequential inoculation with Beta, PN4 Co-inoculation with Beta, Alpha, VP41, new selection (upco- is a by-product of citric acid degradation via Eliminate as much as possible yeast lees ming) pyruvic acid and -acetolactic acid (figure Lower temperature during MLF Sequential with Lalvin 31, VP41, new selection (upcoming) Temperature during AF/MLF 18-20°C 1). However, this is not the only mecha- Quick stabilization with SO2 at end of MLF Yeast lees contact nism involved in the production of diacetyl, Delayed SO addition (minimum 1 week) as pyruvic acid is an intermediate metabo- 2 lite, which can also derive from the glucose Table 2. Shaping the diacetyl content of wine

To summarize...

Many factors influence the diacetyl content of wine and, therefore, the buttery character in wine. To properly modulate the contribution of this character, several winemaking procedures can be worked on to achieve the desired effect, from a major impact to a slight one. Two of the most important factors are the choice of ML bacteria used to achieve MLF, and the timing of inoculation with those bacteria. Our program of ML bacteria characterization for diacetyl allows us to better understand ML bacteria and recommend those required to influence the production of the desired compounds. In sequential inoculation, some strains of ML bacteria, such as the VP41 and Lalvin 31, are recognized as low producers, whereas PN4 and Beta are higher producers. The timing of inoculation with bacteria starters is very important, as co-inoculation will always yield lower diacetyl levels in wines, so low in fact that we can propose very low diacetyl solutions through co-inoculation. To choose the right ML bacteria for your wine, as well as the right procedure, please consult your Lallemand representative. References available upon request.