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New World Wine Maker Blog

Understanding Wine Lees!

Reproduced with permission from the Dept of Food Science & Technology, Virginia Tech

The Nature of Wine Lees
During aging sur lie, yeast components are released into the wine. These macromolecules can positively influence structural integration, phenols (including tannins), body, aroma, oxygen buffering, and wine stability. Some macromolecules can provide a sense of sweetness as a result of bridging the sensory sensations between the phenolic elements, acidity, and alcohol, aiding in harmony and integration.
Mannoproteins in the yeast cell wall are bound to glucans (glucose polymers), which exist in wines as polysaccharide and protein moieties (Feuillat, 2003). They are released from the yeast cell wall by the action of an enzyme, β-1,3-glucanase. β-1,3-glucanase is active during yeast growth (fermentation) and during aging in the presence of non-multiplying yeast cells. Stirring increases the concentration (Feuillat, 1998).
Lees and mannoproteins can impact the following:

integration of mouthfeel elements by interaction between structural/textural features
reduction in the perception of astringency and bitterness (Escot et al., 2001; Saucier, 1997)
increasing wine body
encouraging the growth of malolactic bacteria and, possibly, yeasts
preventing bitartrate instability (Lubbers et al., 1993; Moine-Ledoux, 1996; Moine-Ledoux and Dubourdieu, 2002; Waters et al., 1994)
interacting with wine aroma (Lubbers et al., 1994)

The amount of mannoprotein released during fermentation is dependent on several factors, including the following:

Yeast strain: Large differences are noted among yeasts in the amount of mannoproteins produced during fermentation and released during autolysis.
Must turbidity: Generally, the more turbid the must, the lower the mannoprotein concentration (Guilloux-Benatier et al., 1995). Mannoproteins released during fermentation are more reactive than those released during the yeast autolysis process in modifying astringency. This helps provide additional justification for measuring the non-soluble solids of juice pre-fermentation.

Wines aged on lees with no fining have mannoproteins present, while those fined prior to aging have a large percentage of mannoproteins removed. Periodic stirring sur lie increases the mannoprotein concentration, and increases the rate of β-1,3-glucanase activity. Generally, yeast autolysis is relatively slow (in the absence of glucanase enzyme addition) and may require months or years to occur, limiting the mannoprotein concentration (Charpentier and Feuillat, 1993).
The impact of lees components such as polysaccharides on astringency can cause an increase in the wine’s volume or body. Lees contact is particularly effective at modifying wood tannin astringency by binding with free ellagic tannins (harsh tannins). Sur lie storage can reduce the free ellagic acid by as much as 60% (via precipitation), while increasing the percentage of ellagic tannins bound to polysaccharides by 24% (Ribéreau-Gayon et al., 2000).
In the Burgundy and other regions, red wines are aged on their lees in conjunction with the addition of exogenous β ‑1,3-glucanase enzyme. This procedure is an attempt to release mannoproteins, which winemakers believe may enhance the suppleness of the wine, while reducing the perceived astringency.
Several alternative methods of increasing mannoprotein levels have been suggested (Feuillat, 2003), including the following:

selection and use of yeast which produce high levels of mannoproteins during the alcoholic fermentation
yeast which autolyze rapidly upon completion of alcoholic fermentation
addition of β-1,3-glucanase to wines stored on lees
addition of exogenous mannoproteins (proprietary products), prepared from yeast cell walls, to wines on lees

Lees Management Considerations.
Table 1 shows some important practical winemaking considerations regarding lees management.
During fermentation, the level of macromolecules continually rises, peaking at approximately 270 mg/L, by which time they contain 82% sugar and only 18% protein (Feuillat, 2003).
Guilloux‑Benatier et al. (1995) found a relationship between the degrees of must clarification and the amount of yeast macromolecules recovered in the wine. When the must was not clarified, there is no production of yeast macromolecules.
Table 1Lees Management Considerations

Non-soluble solids level

Method of stirring

Frequency and duration of stirring

Type and size of vessel

Duration of lees contact

MLF

Timing and type of racking

SO2 timing and level of addition

Frequency of barrel topping

However, mild must clarification, such as cooling for 12 hours, increased the amount of yeast-produced macromolecule production by 76 mg/L, and heavy must clarification, such as bentonite fining, increased the production by 164 mg/L. Boivin et al. (1998) found that the amount of macromolecules produced will vary between 230 and 630 mg/L, and that they will contain 20 – 30% glucose and 70 – 80% mannose.
During lees contact, the composition of the wine changes as the yeast commence enzymatic hydrolysis of their cellular contents. One important feature is the process of proteolysis, whereby proteins are hydrolyzed to amino acids and peptides. These compounds result in an increase in the available nitrogen content of the wine. Amino acids can act as flavor precursors, possibly enhancing wine complexity and quality.
Yeast-derived macromolecules provide a sense of sweetness as a result of binding with wood phenols and organic acids, aiding in the harmony of a wine’s structural elements by softening tannins.
It is important to differentiate between light lees and heavy lees. Heavy lees can be defined as the lees which precipitate within 24 hours immediately post-fermentation. They are composed of large particles (greater than 100 micrometers) and consist of grape particulates, agglomerates of tartrate crystals, yeasts, bacteria, and protein-polysaccharide-tannin complexes.
Light lees, on the other hand, can be defined as those that precipitate from the wine more than 24 hours post-fermentation. These are composed mainly of small particles (1- 25 micrometers) of yeasts, bacteria, tartaric acid, protein-tannin complexes, and some polysaccharides.
There is no value in storing wine on heavy lees. Indeed, such storage can result in off aroma and flavors, and a depletion of sulfur dioxide. Light lees storage, however, can have a significant advantage in structural balance, complexity, and stability.
Lees stirring and the frequency of stirring is important, both as a practical and stylistic consideration. Feuillat and Charpentier (1998) have demonstrated that periodic stirring of the wine while on lees increases the mannoprotein level and the amount of yeast-derived amino acids, and that wines aged on their lees in barrel exhibit an increase in colloidal macromolecules.
Stirring generates an oxidative process which increases the acetaldehyde content, and which may increase the acetic acid concentration. Stirring also changes the sensory balance between fruit, yeast, and wood by enhancing the yeast component, and reducing the fruit and, to a lesser degree, the wood component.
Additionally, stirring may have the effect of enhancing secondary chemical reactions, possibly as the result of oxygen pick-up. Stuckey et al. (1991) demonstrated increases in both the total amino acid content and wine sensory score in wines stored for five months without stirring. The non-stirred wine was perceived to have greater fruit intensity.
MLF reduces the harshness of new oak and aids in the development of complex and mature flavors. Traditionally, stirring is continued until MLF is complete. After that, the lees are said to become more dense, which aids in clarification.
During barrel aging, what we are looking for is slow, well-managed, and controlled oxygenation. Some lees contact may allow for this oxygenation, and lees aid in the prevention of oxidation.
In Burgundy, wines are traditionally racked off the lees in March, usually the time when MLF is completed. Frequently this is an aerobic racking off the heavy lees, then back into wood on light lees, followed by an SO2 addition. Leaving the wine on the light lees helps to nourish the wine. The addition of SO2 helps to protect the wine from oxidation. A subsequent racking often occurs in early July, and is in the absence of air.
Timing of SO2 additions, and the quantity of SO2 added, are important stylistic considerations. Early use of SO2 increases the number of components that bind to subsequent additions of SO2. The addition of too much SO2 counters the wood flavors and limits oxidation reactions, while too little SO2 may allow the wine to become tired and over-aged.
Production considerations, such as the timing of MLF, the method of barrel storage, and time of bottling, are factors influencing SO2 levels. Barrel topping is an aerobic process that can result in excessive oxidation. Additionally, wines that spend a second winter in the cellar tend to lose their aroma unless the wine is particularly rich.
Delteil (2002) compared two red wines. One wine was barrel-stored on light lees for 9 months; the other, racked several times prior to barreling, was stored for the same period without lees. These two Syrah wines differed significantly in their palate and aroma profiles.
The wine stored sur lie had a much lower perception of astringency and a greater integration of the phenolic elements. The sur lie wine also had a lower perception of oak character, resulting in a higher perception of varietal fruit.
Lees contact is particularly effective at modifying wood tannin astringency by binding with free ellagic tannins, thus lowering the proportion of active tannins. Sur lie storage can reduce the free ellagic acid by as much as 60%, while increasing the percentage of ellagic tannins bound to polysaccharides by 24% (Ribéreau-Gayon et al., 2000).
The following is a review of the impact of lees on wines.

Lees, Color and Mouthfeel.High lees concentration can reduce color, as a function of adsorption onto the yeast cell surface.  Additionally, lees adsorb oxygen which can limit the anthocyanin-tannin polymerization, resulting in an increase in dry tannin perception. This may or may not be off-set by the release of lees components which can soften mouthfeel.

Lees and Wine Aroma. Aroma stabilization is dependent upon the hydrophobicity (ability to repel water molecules) of the aroma compounds. The protein component of the mannoprotein fraction is important for overall aroma stabilization (Lubbers et al., 1994). Such interactions can modify the volatility and aromatic intensity of wines.

When wine is aged on its lees with no fining, mannoproteins are present and are free to interact and to fortify the existing aroma components. When wines are fined prior to aging, mannoproteins are removed and will not be present to augment the existing aroma components. Additionally, when wines are cross‑flow filtered, eliminating a certain percentage of macromolecules, the loss of color intensity, aroma, and flavor can be noted.

Lees and Oak Bouquet. Lees modify oaky aromas, due to their ability to bind with wood-derived compounds such as vanillin, furfural, and methyl-octalactones.

Lees and Oxidative Buffering Capacity. Both lees and tannins act as reducing agents. During aging, lees release certain highly-reductive substances which limit wood-induced oxygenation. Wines have a higher oxidation-reduction potential in barrels than in tanks. Inside the barrel, this potential diminishes from the wine surface to the lees. Stirring helps to raise this potential.

This is a primary reason why wines stored in high-volume tanks should not be stored on their lees. Such storage can cause the release of “reductive” or sulfur-containing compounds. If there is a desire to store dry wines in tanks sur lie, it is recommended that the lees be stored in barrels for several months, then added back to the tank (Ribéreau-Gayon et al., 2000).

Lees and White Wine Protein Stability. The greater the lees contact, the lower the need for bentonite or other fining agents for protein stability. It is not believed that lees hydrolyze grape proteins, or that proteins are adsorbed by yeast. Rather, lees aging produces an additional mannoprotein, which somehow adds stability. The production of this mannoprotein is increased with temperature, time, and frequency of stirring.

Lees and Biological Stability. Guilloux‑Benatier et al. (2001) have studied the liberation of amino acids and glucose during barrel aging of Burgundy wine on its lees. Their studies were done with and without the addition of exogenous β‑1,3-glucanase preparations. They found little or no increase in amino acids in wine stored on lees, versus wine stored on lees with the addition of β‑1,3-glucanase.

Their most significant finding was an increase in glucose concentration, from 43 mg/L in the control wine, to 570 mg/L in wine stored on its lees, to 910 mg/L in wine stored on its lees with added β ‑1,3-glucanase. The finding of this relatively large amount of glucose led these authors to speculate that the growth of the spoilage yeast Brettanomycesin barreled wine may be stimulated by the availability of this carbon source.

Lees and Bitartrate Stability. Mannoproteins produced by yeast can act as crystalline inhibitors. The longer the lees contact time, the greater is the likelihood of potassium bitartrate stability.

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Interview with Nadia Barnard – winemaker at Waterkloof

Q:  Where do you originate from ?

“I was born in Pretoria.”

Q : How does someone from Pretoria get to be winemaker in the Cape?

“My Dad worked for a large company and was transferred to Somerset West.” She continued “Once the novelty of the ocean began to wane I realised the entire country was covered in grape vines. Then at school, Bloemhof in Stellenbosch. some of my friend’s parents were involved with making wine or growing grapes.” Then added, with great enthusium “ “My Dad often took me to wineries while he was buying wine. He often gave me taste and I enjoyed what I tasted.”

 Q :When you graduated where did you first work ? 

“Well I  did my first student vintage at  Flagstone. Then did another vintage there in 2007. Then I set out to travel the world ! I did a vintage at Coonawarra in Australia.  Then moved to the Northern hemisphere and did a vintage in Burgundy, In 2008 I worked a vintage at Vergelegen. Then back to New Zealand for a short stint. Then back north for a vintage at Chablis.

Q  When did you settle back in South Africa ? 

“I joined the Waterkloof team at the end of 2008 as assistant winemaker and was appointed winemaker for the 2013 vintage

Q   Do you consider your winemaking to be different to others ? 

“At Waterkloof we try and not interfere with nature in the winemaking but it is in the vineyard that we really differ. Winemaking is all about taking your time and getting to know your vineyards.

Q  Does having your vineyards certified fully biodynamic make a difference ?

“Of course it does. Our vineyards are chemically free and we make all our own compost using traditional biodynamic methods. This ensures healthy soil full of bacteria and oxygen  and as a result a perfectly balanced vineyard ideal for the production of the best grapes”

Q   And what about the Percherons ?

“I must say they are an added attraction and serve a purpose in the narrowly planted old vines”

Q  You mention old vines , you have been making a wine from 40 year old cinsaut ?

“Yes , and it has turned out particularly well. It was given four and a half stars in Platter ! Described as having ripe blackberry notes, dark cherry and plum.”

Q  With the mention of old vines then there is you at the tender young age of 30 in charge ? 

a somewhat bashful reply, “I accept I carry a great responsibility but the entire team at Waterkloof are dedicated to producing the best.”

Q  What do you consider  your greatest achievement as a winemaker ?

“Bottling my first Waterkloof Sauvignon blanc”

Q  Have you developed anything “secret” that makes your winemaking different any others ?

“No, not really. Leading up to vintage I go back to tasting the grapes all the time”

Q   How important is modern winemaking equipment ? 

“Not very. Although the winery building is strikingly modern the winemaking is pretty conventional. We do have a new Coquard press which is based on the traditional basket press.”

Q  If Nadia is not in vineyard or cellar where is she most likely to be ?

“With the winery situated high up in the Schapenberg you would probably find me powering along a trail in the mountains on my mountain bike !

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Napoleon’s Box Wine

Certain wine farms in South Africa take a great deal of pride in reminding us that Napoleon Bonaparte drank their wine! In some cases this is quite possible. These people love to romanticize the idea of sharing history with others by drinking this same wine; as if wine were a cosmic worm hole of experience, which it somehow is. Although, in this case, if people were really drinking the same wine that Napoleon did whilst in exile on St Helena, they would be running the risk of dying of both stomach cancer and arsenic poisoning. This is definitely not an experience anyone in their right mind would happily sign up for.

On top of that, wine spoilage was such a problem back then – almost an inevitability. The common ‘horse sweat’ taint (how anyone came up with that descriptor still perplexes me) of Brett or other spoilage organisms was cleverly masked with high residual sugar. And voilà – we have the sweet wines of Constantia. Ironic now that we know residual sugar is the buried treasure that any and all fungus will seek and find, and in hindsight probably not the best solution to hide wine spoilage. Sulphur was administered in a primitive soaked-rag form; sterilisation and sanitation was minimal; and vineyard practices hardly the art form they are today. Combine this with the low alcohol of an incomplete fermentation and it is an absolute miracle Napoleon didn’t receive shipments of vinegar from South Africa.

The overall point is that the Kings of Mesopotamia, to the Noble Dukes of Medieval Burgundy, were likely drinking a wine that could barely make the cut of box wine these days. So high has the standard become! This applies not only to wine, but to food as well. Hundreds of years of work has gone into creating your average fast food meal, which probably has just enough nutrients to sustain a human throughout their whole life if they were to have it every day (though I don’t recommend it).

Much like the oil crisis, the “wine quality crisis” (absolutely not an official term) is effecting everyone in a positive way, unless, of course you want to make money selling wine. Us, the stricken consumers, aim to pay low prices for wines made under the highest sanitary conditions of all time, and with the most advanced technology of Oenology. We want the best wine for the lowest possible price. The producers, though, must produce (as they do) at an incredible standard to simply even have the “audacity” to sell above the average price. As a foreigner myself, it’s quite shocking what even the most expensive South African wine would cost once converted back into Pounds Sterling (UK). For example R600 translates to just under £30 – at that cost you’d be lucky to buy a drinkable French wine, let alone something the equivalent to the top bracket wines of South Africa.

I always imagined even a middle class European coming to South Africa to realise the quality their money could fetch and never understood why wine tourism never caught on to the universal extent that it should have. While it always seemed an injustice to the rising quality of South African wine, perhaps it is best to bask in the undiscovered glory of the industry as it is today, with the wake of globalisation, overnight luxuries can move into price brackets designated only for millionaires, as we’ve seen in France. Don’t take my wine away!

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Anchor Alchemy red blends, another exciting innovation from Anchor Yeast

Anchor Alchemy Red Blends III and IV were developed to respond to the industry’s need for similar innovation to Alchemy Blends I and II for white wines. Following this overwhelming success, Oenobrands is proud to launch Alchemy Blends for red wines. These two novel blends for red wine application have been scientifically formulated by Anchor Yeast, in collaboration with the Australian Wine Research Institute.

Anchor Alchemy III Complex Red – produces complex red wines with good structure and body.

Anchor Alchemy IV Intense Red – produces well-rounded and smooth red wines with significantly higher aroma intensity.

Common to both blends is their significant contribution to aromatic fruit intensity due to a high level of total esters and ethyl hexanoate. This is further enhanced by the inclusion of -damascenone and a reduced level of methoxypyrazines, which can mask fruity characteristics. These blends offer winemakers the opportunity to create wines with increased complexity and more intense aromas. Anchor Alchemy III Complex Red and Anchor Alchemy IV Intense Red are available from Oenobrands distributors.

For more information, please contact Oenobrands at info@oenobrands.com or www.oenobrands.com

This is another ADVANCED WINEMAKING SOLUTION brought to you by OENOBRANDS.

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How quickly does oxygen disappear from white wine?

by Wessel du Toit, Daniella Fracassetti, Carien Coetzee, Andreja Vanzo & Davide Ballabio – for Wineland Magazine

Introduction

Oxygen plays an important role in wine production. The exposure of red wines to small amounts of oxygen can be beneficial to the wine’s development in terms of colour stability and the softening of tannins during barrel ageing. However, in general the addition of oxygen in white wine is not wanted. This is due to the development of a brown colour, a decrease in fruitiness in the wines and an increase in acetaldehyde levels. Factors affecting the consumption of oxygen in white wines are not completely clear, which is probably due to the large chemical differences existing between white wines from different cultivars, areas and vintages. The main aim of this work was thus to follow the decrease in dissolved oxygen concentrations in a number of white wines and to try to link these with the chemical composition of the wines.

Materials and methods

We obtained 13 young Sauvignon blanc wines from the 2010 vintage just after the completion of alcoholic fermentation. These wines were collected from different commercial wineries before any SO2 additions were made after alcoholic fermentation and transported to the Department of Viticulture and Oenology, Stellenbosch University. The wines were collected in 20 ℓ canisters into which N2 gas had been previously blown. The pH of these wines ranged from 3.2 to 3.5 with alcohol levels ranging from 12.3% to 13% v/v. Each wine was then divided into two treatments, one that received no SO2 addition, with the other half receiving 30 mg/ℓ SO2. All the wines were then saturated with oxygen and the wines placed at 37°C for 60 days to enhance the oxidation process. Oxygen levels were monitored daily during this period and wine samples drawn at the beginning and end of the experiment for chemical analyses. Analyses included free and total SO2, glutathione (GSH) analyses, oxidised GSH, grape reaction product, range of phenolic compounds such as caffeic acid, caftaric acid, catechin, coumaric acid, ferulic acid etc., Cu, Fe, as well as absorbencies at 280 nm (total phenolics) and 420 and 440 nm (brown and yellow colour).

>> CLICK HERE TO READ FULL ARTICLE

 

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Tasting notes from a tasting room assistant

I have not been a part of the wine industry for a very long time (a full four years to be exact), therefore I am very cautious to make generalisations of what I find and experience in industry. But after having some discussions with friends that have also had the glorious job of being a wine tasting room assistant, I have learned that there are certain things and people that are bound to cross your path if you find yourself presenting wines to at least 20 different people in one day.

Let me start by putting things into perspective, as I used to be a tasting room assistant myself. Back in my second year at varsity, I worked part-time in a tasting room for about six months to gain practical experience in the wine industry. The farm was on the smaller side and situated on the outskirts of Stellenbosch, thus the tasting room did not have an extremely large capacity. On the weekends the operations were singlehandedly run by one of the tasting room assistants, which usually led to either one of the following two extremes: a) a chaotic day of running around like a headless chicken or b) dying of boredom and wishing that one of the security guards at the gate would decide to come up for a tasting. Lucky for me, the latter situation occurred less frequently.

Given this experience I am well aware that presenting tastings and selling wines is not always a fun job- especially if you work on your own. But having said that, I also believe that it is one of the most rewarding jobs you can have as a student. The abundance of different people you meet is an assurance that there will never be a dull day as long as you meet someone new. Don’t get me wrong, I know that every now and again you will come across a know-it-all customer that claims to have a degree in Pinotage, but he (or she) can’t tell a Pinot gris from a Pinot noir. And of course there are the dreaded days when a group of 20 students arrive to create havoc in the bite-sized tasting room. To the great relief of tasting room staff, more often than not, the general public is curious and eager to learn more about the farm and the wines- regardless of their own level of wine expertise.

My personal favourite customers were always the “wine tasting virgins”. They were easily identified as they were usually confused by the placement of a spittoon on the table or used phrases such as “What should I be smelling in this wine?”. Although they were cautious and unsure individuals at first, they quickly warmed up to a person and always had interesting questions to ask and showed a genuine interest in what you were telling them. It was self-satisfactory to know that you are passing on some of your wine knowledge and you experienced a sense of proudness as they left the tasting room to move on to the next farm, almost like a parent must feel when their child moves off to college- I have done my job the best I could, the rest is up to you (queue single tear drop from left eye).

Working in a tasting room also presents you with the incredible opportunity to meet and mingle with winemakers from other farms that are keeping an eye on the competition. Hearing their personal philosophies about winemaking and views about the industry instilled a new sense of excitement in me and reminded me that our industry is surely one of the most unique ones in the world and certainly one to be very proud of.

So even though being a tasting room assistant isn’t seen as being one of the most glamorous jobs in the wine industry, it does expose you to a great number of people that find themselves in it- from the amateur wine taster to the winemakers and producers that are making waves and revolutionising the way we produce, market and sell wines and everyone else in-between. It’s a hands-on job that allows you to make a contribution to the industry every time you present a glass of wine and therefore it’s a job to be proud of!

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