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New World Wine Maker Blog

Starting your fermentation right: nutrient supplementation

By: Denise M. Gardner

Based on the number of questions I have received this year about yeast assimilable nitrogen (YAN), it looks like more winemakers are taking it upon themselves to measure YAN on pre-harvested fruit or on incoming juice.  This can be a great step in improving wine quality!  Measuring YAN offers several benefits to winemakers, including:

  • Minimizing the incidence of hydrogen sulfide development in the wine.
  • Enhancing varietal character by producing cleaner wines with adequate and specific nitrogen supplementation throughout primary fermentation.
  • Minimizing excessive nutrient supplementations, in which left-over nitrogen (after primary fermentation) may act as nutrient sources for spoilage yeast and bacteria.
  • Reducing unnecessary work for your employees by minimizing problematic production situations (e., fixing wines with hydrogen sulfide). Such actions could have economic benefit (i.e., reduction in supplies, reduction in time/labor)

Below is a quick refresher for those that may have questions about YAN.

The Basics

  • YAN = Ammonia Concentration + Primary Amino Acid Concentration given in the units: mg N/L (read: milligrams of nitrogen per liter)
  • Most suppliers (g., Lallemand, Scott Labs, Enartis, Laffort) will providerecommendations on what to add in low, medium, or high YAN situations. Make sure you consult your handbooks or supplier websites for their product-specific recommendations.
  • At the start of fermentation, you want to avoid adding diammonium phosphate (DAP) or complex nutrient additions that contain DAP (g.,Fermaid K) when hydrating your yeast. Use hydration-specific products like GoFerm or Nutriferm Energy.
  • Most suppliers recommend making 2 additional nitrogen supplementation additions during primary fermentation and after inoculation. If only making 1 nutrient addition after inoculation is practical for you, add your nitrogen supplement at about 1/3 of the way through primary fermentation (e., 1/3 drop in sugar depletion).

Yeast hydration nutrients are an important component of re-hydrating freeze dried yeast. Winemakers should make sure to avoid DAP additions at this stage. Inoculation photo by Denise M. Gardner

Yeast hydration nutrients are an important component of re-hydrating freeze dried yeast. Winemakers should make sure to avoid DAP additions at this stage. Inoculation photo by Denise M. Gardner

A Review: Why to not add DAP at yeast hydration/inoculation

YAN is composed of inorganic (ammonium ion) and organic (primary amino acid) nitrogen components.  Amino acids are brought into the yeast cell through transport across the cell membrane.  The presence of alcohol and ammonium ions (i.e., DAP) inhibit amino acids from being brought into the cell.  This is why winemakers are advised NOT to add DAP at inoculation or at the beginning of fermentation, as yeast can actively absorb organic nitrogen in the juice (aqueous) environment.

Once alcohol concentrations begin to increase, as a result of primary fermentation progression, transport of amino acids from the wine into the yeast cell will be inhibited.  Therefore, the primary source of nitrogen will then come from inorganic sources, such as DAP.  A more thorough summary of how nitrogen is utilized by yeast can be found at the following pages:

In general, winemakers can select from three different kinds of nitrogen-based products to add during fermentation:

  • Hydration Nutrients (g., GoFerm, Nutriferm Arom, etc.)
  • Complex Nutrients (g., Fermaid K, Nutiferm Advance, Superfood, etc.)
  • Diammonium Phosphate or DAP

Need more direction on when to add which nutrients?  Look no further!  We have a practical fact sheet waiting for you at the Penn State Extension website.  As a general rule of thumb, remember to make your YAN additions based on the volume of wine that you are treating.  For whites, roses, and some reds (e.g., hot pressed Concords), YAN additions will be made based on the juice volume.  For most other reds, YAN additions should be based on the must volume.

Dealing with Low YAN Fermentations

Low YAN fermentations are defined as having less than 125 mg N/L in the must/juice at the start of fermentation.  In these situations, it’s essential for the winemaker to provide enough “food” for all of the yeast during primary fermentation.

Depending on the reference, most scientific literature will recommend adding up to 200 – 250 mg N/L.  This concentration of nitrogen should provide adequate supplementation for the entire biomass throughout the duration of fermentation.

Be aware that if you are using a HIGH NITROGEN DEMANDING YEASTstrain (e.g., BM45, ICV-GRE, among others), however, you may be required to add additional supplementation.  If you are starting with a low YAN situation and would like to use a high nitrogen requiring yeast strain, we recommend contacting your supplier for specific nutrient addition instructions.

Dealing with High YAN Fermentations

Many suppliers define a high YAN fermentation anywhere above 250 mg N/L.  However, some YANs from Pennsylvania grown grapes are at concentrations greater than 400 mg N/L!  This YAN concentration can create a challenging fermentation and processing situation for the winemaker.

Due to the excess amount of available nutrients in these situations, yeast can grow and reproduce quickly, which often leads to very rapid and hot fermentations.  The speed and temperature of fermentation can affect the aromatics and quality of the wine (i.e., fast fermentations often lead tosimpler aroma and flavor profiles).  This may not be an issue with some fermentations, but for many white, rosé, or fruit (other than grapes)-based fermentations, aromatic retention should be a priority by the winemaker.

Higher concentrations of the inorganic component of YAN can lead to a high initial biomass of yeast.  This is a problem because the rapid increase in yeast populations can lead to starvation by the majority of the yeast by mid- to late-fermentation, especially if there is not enough nutrition to fulfill all of the yeast during fermentation.  Yeast starvation leads to yeast stress, and one of the stress responses by yeast is the production and release of hydrogen sulfide.  Therefore, having a high YAN at the start of fermentation may cause hydrogen sulfide issues in the wine by the time fermentation is complete.

What should you do if you have a high YAN?

  • First, always reference your supplier recommendations. Each year, suppliers publish current guidelines for how and when to add various nutrients during fermentation.
  • I’ve found it helpful to document trends in high YAN fermentations. For example, if you notice that a variety with a routine high YAN year-to-year, note the years where hydrogen sulfide becomes an issue.  Good record keeping during primary fermentation can remind you what you did during production.  You may need to alter these practices for the following vintage year.
  • If all else fails, refer to Penn State’s Wine Made Easy Fact Sheet on Nutrient Supplementation during Primary Fermentation

Additionally, high YAN concentrations may leave some nitrogen left over by the end of fermentation and could remain in suspension in the finished wine.  This excess “food” could be available for other microorganisms (like acetic acid bacteria or Brettanomyces), which could potentially lead to spoilage problems if the wine is not properly stabilized.  In high YAN situations, it is especially important to ensure that the wine is stabilized with adequate sulfur dioxide additions and by minimizing other risk factors (e.g.,temperature control of the wine).

It is also be researched that high starting YAN values may led to increased concentrations of ethyl carbamate. Ethyl carbamate is naturally produced by fermentation, but it is a mild carcinogenic compound.  For this reason, many countries have legal maximum ethyl carbamate concentrations in wine.  For more information on ethyl carbamate, please see this guide published by UC Davis or this Extension report from Virginia Tech’s Enology Grape Chemistry Group.

Our Understanding of YAN is still Developing

Every year, YAN is a big topic of conversation amongst industry suppliers and academics.  Current investigations include:

  • The impact of primary amino acid uptake as a function of temperature, reported by Cornell University and discussed at the 2016 American Society of Enology and Viticulture (ASEV) – Eastern Section conference (Missouri) in a presentation by Scott Labs.
  • YAN recommendations for hybrid varieties produced in the Mid-Atlantic, a topic discussed by Dr. Amanda Stewart from Virginia Tech University during the 2014 PA Wine Marketing & Research Board Symposium. This includes looking at other nutritional factors beyond nitrogen supplementation, which was also discussed at the ASEV-Eastern Conference in 2016 by Scott Labs.
  • Optimal nutritional strategies for challenging fermentations, which is often reported in supplier catalogs like the Scott Labs 2016 Handbook
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Louis Van Der Riet – Winemaker a De Krans Winery in Calitzdorp

Q. Where did you originate ?

“I was born in Worcester on 13th February 1987.”

Q. Was it a Friday ?

“Funny enough it was but in my case it has been a lucky day !”

Q. Where did you study ?

“I went to Elsenburg where I  was successful in diplomas Viticulture and Oenology.”

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

“No, I think all winemakers can only strive to bring forward the heart of the wine by guiding it in the right direction.”

Q. How involved do you get in the vineyard ?

“As much as possible , but that is not nearly enough.”

Q. Do you have any varieties that you prefer to work with ?

“I like our traditional Chenin blanc and of course port varieties where Touriga Nacional is my favourite.”

Q. Have you been influenced by any particular winemaker or region ?

A very enthusiastic reply. “ Oh yes, the Douro in Portugal has definitely had an effect  on the way I think about vineyards , Wine and winemaking.  Also in South Africa we are blessed with amazingly talented winemakers from small to massive production cellars. I try to learn from everyone I meet.”

Q. What would you consider your greatest achievement as a winemaker ?

With a great big grin. “To get through the harvest without losing your sanity ! I have been blessed with a list of lifetime achievements, but the most special was when I released my first own label wine.”

Q. What secrets have you “developed” that make you different to others ?

Now all serious. “No secrets. A lot of hard work and long hours in the cellar during harvest to grind the work out. As soon as you think you are better  than to pull pipes around  you’ve lost the plot and never think you know everything about wine !!” It is the quest to learn  that makes your wine different.”

Q. How important is modern winemaking equipment in your winemaking ? 

“Not really an issue. I work in an old cellar with old equipment. We have a very hands on approach to winemaking. Literally. We still empty some of our lagers  with buckets into an old basket press. However, I think modern knowledge is very important. To keep up with new research and to be able to think modern knowledge is very important. To keep up with and use new research and be able to understand what is happening and be able to change, adapt or implement where necessary is vitally important.”

Q. What about the future ?

“I’ve always had a passion for Portuguese  varieties. I think I have only scratched the surface about understanding how to plant and produce great wines  from these varieties. I do believe these varieties are excellently suited to our South African  climate and terroirs and I would, one day, like to see more wineries planting and producing great quality Portuguese varietal wines and  South Africans to understand and develop a love for these wines.”

Q. Haven’t you already  done this ?

“I suppose you refer to the Diners Club Young Winemaker of the year in 2014 when I was a finalist with a dry red wine made from Tinta Roriz . Traditionally a port variety but we have proved we can make outstanding natural dry reds from it.”

Q. That wasn’t all ?

“Yes, we have done well in a number of competitions with dry wines from port varieties. The Novare South African Terroir Awards has been kind to us when we won a National award for our 2013 Tinta Roriz.” He continues with a smile “There is a lot more to come. Just watch this space !”

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Ten Things to Do At a Wine Farm (Besides Drink Wine)

Ever woken up one weekend-morning and felt like going for a wine tasting, but the family is visiting and Grandma or Uncle Sam doesn’t drink wine and so you think all hope is lost? Think again! Lucky for you, these days wine farms and estates offer so much more to do than just the usual stuff like wine tastings and restaurants. Here are a few things you can keep the family (or dry friends) busy with whilst you’re tasting some wines… Chances are, you will probably enjoy them too.

  1. Cellar Tours
    More and more wine farms are opening up their cellar doors to the public to give them an insight as to how their wine is made and what exactly goes into making an outstanding bottle of wine. Each winemaker and winery has their own way of going about their daily task and no two wineries are the same, therefore you will always learn and experience something new on a cellar tour. Make sure to phone the winery beforehand to hear if they do offer cellar tours and make a booking or appointment if needed.
  2. Take a Hike
    Given the beautiful setting we find most of our wine farms in, a lot of them now have hiking trails that are open to the public. Trails differ in length, but are usually not extremely difficult and even the most inexperienced hikers will find trails that they are comfortable with. In the Western Cape, we are also spoiled for choice as to what kind of scenery we can enjoy on our routes. Choose from the scenic mountainous routes, darker forest trails or simply take a stroll through the vineyards- just check with the tasting room staff which vineyards you are allowed to move through.
  3. Ride a Bike
    If walking is not for you, mountain bike (MTB) trails on wine farms have also risen in popularity. Beautiful trails wind past lusciously green vineyards and through natural veld and fynbos fields. Several farms now host regular MTB events, which you can enjoy as a spectator or participant. And if you’re not ready to compete in a race yet, get the family pedalling together on a Sunday afternoon.
  4. Take a Boat Trip
    If you find yourself in a wine region that is close to a river, chances are that there will be a farm or two that offer boat rides on the river. What better way is there to enjoy the natural surroundings with a delicious cheese platter and maybe a bottle of wine (or grape juice for Grandma). Boat rides are usually scheduled on the hour so make sure to get there early to make your reservation and shop for lovely goodies to enjoy on your cruise. No seasickness guaranteed.
  5. Visit an Art Gallery
    A lot of wineries have recently started to support local artists by displaying their work in art galleries or sculpture gardens at various wine farms. Be it beautiful landscapes or abstract paintings, interesting sculptures or blown glass art- there is something for every cultured soul to enjoy and admire.
  6. Go Fishing
    Some wine estates that are located close to a river or maybe have a large dam on the farm even offer their patrons the opportunity to have a go at catching their own fish. These wineries are ideal for Dad and Uncle Sam to “wet their lines” while the ladies enjoy a glass of Chardonnay- even the kids will have something to do other than play on the same old boring jungle-gym. And for those more adventurous fisherman, certain farms even feature fly-fishing as one of their attractions. Be sure to phone the farm first to make sure their fishing season is open and make a reservation if needed, as it is quite a popular sport.
  7. Go on a Game Drive
    If you would rather sit down and relax while enjoying the beauty that is our winelands, try visiting one of the many wine farms that offer game drives. Experience an informative tour of some of South Africa’s greatest and most beautiful wild animals from lions and cheetahs to springbucks and wildebeests. There are also wine estates that have more exotic animals like reindeer (yes, in Africa). Reservations are usually essential, so make sure to make a phone call to avoid disappointment.
  8. Relax with a Spa Treatment
    Nature not so much your thing? Head on over to the spa for a tantalising facial or a well-deserved pedicure. There are few things more satisfying than receiving a relaxing foot massage whilst enjoying your favourite glass of wine (or a fruit smoothie)- even Uncle Sam could probably do with an invigorating body exfoliation treatment. Every second wine estate now has a day spa so your options are endless and there are spas to suit everyone’s needs and pockets.
  9. Play a Game of Boules
    Long gone are the days where boules were considered to be a sport for old people. It can now be enjoyed by the whole family on your next visit to a wine farm. It is a great way to get up and get active and it is also ideal for your next team-building exercise at work. You can even enjoy a wine tasting and light lunch at the restaurant after you’ve all worked up a sweat on the greens and had a few good laughs. Many farms also have other fun lawn games that can be enjoyed, free of charge.
  10. Test Your Aim with Clay Pigeon Shooting
    And for those looking for a bit more excitement in their life and power in their hands, you can always have a go at clay pigeon shooting. This age old tradition is now being offered at a few wineries around the Cape and is great fun for both participants and spectators. You won’t be bringing home a duck for Sunday’s lunch, but at least you will be able to get rid of some of your frustrations.

Clearly there is something to do for everyone at a wine farm and there should never be an excuse not to visit one- not even the complaints from Gran and Uncle Sam. There are loads more fun activities and attractions at our wineries, but who really needs to be convinced if there is wine to be drank?

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Making red wine from fruit high in potassium

While the issue is quite challenging to address in an established vineyard, processing grapes from high pH fruit, or fruit that has the potential to create a high pH wine (>3.70), as a result of high potassium (K or K+) concentrations is also a challenge for the winemaker.

Concentrations of 22 – 32 mmol/L K+ (860 – 1,279 mg/L K+) are considered “normal” ranges for wine grapes (Somers 1977, cited byMpelasoka et al. 2003), while ranges in the 27 – 71 mmol/L K+ (1,056 – 2,776 mg/L K+) are considered “high” (Somers 1975, cited by Mpelasoka et al. 2003) and may lead to potential winemaking problems.  Grapes and juice that come in with high levels of potassium can lead to a series of difficulties for winemakers including:

  1. High potassium concentrations can cause large increases in pH during primary and malolactic fermentations, which drive the finished wine into a high pH (>3.70) range.
  2. Color hue, intensity, and stability of red wines can be negatively affected.
  3. High pH wines produced throughout the Mid-Atlantic may lead to negative perceptions associated with taste and mouthfeel of both white and red wines.
  4. As pH is a big driver in wine stability, higher pH’s will have impacts on the microbial stability (both in terms of microflora and inhibition of growth), sulfur dioxide levels and efficacy, color stability of red and rosé wines, stability of tartaric acid, and protein stability.
  5. Higher pH’s leads to an increase in oxidative potential, which may cause premature oxidation for young wines.

Figure 1: Color instability problems associated with 2013 Chambourcin wines. The sample on the right is from our Biglerville (Adams County) research site, which we later discovered is associated with high potassium in the fruit and wine. The sample on the left is from our North East (Erie County) site, which is more representative of the color hue and intensity associated with Pennsylvania-produced Chambourcin. Photo by: Denise M. Gardner
Figure 1: Color instability problems associated with 2013 Chambourcin wines. The sample on the right is from our Biglerville (Adams County) research site, which we later discovered is associated with high potassium in the fruit and wine. The sample on the left is from our North East (Erie County) site, which is more representative of the color hue and intensity associated with Pennsylvania-produced Chambourcin. Photo by: Denise M. Gardner
Although the articles listed below are not peer reviewed, previous attention has been given to high potassium winemaking issues.  Some of the content relayed in these 2 articles will not be discussed in this blog post:

  1. Really, really high pH remedies from Wines & Vines: a discussion on potassium concentrations increasing the pH of wine and utilization of ion exchange if the problem is not prevented
  2. High pH and high potassium wines produced in Colorado from White Hall Vineyards: Includes a discussion pertaining to malic acid concentration in high pH fruit. (Author’s note: This article discusses adding tartaric acid prior to fermentation, but not exceeding a TA of 8.0 g/L while hitting a pH of 3.60, ideally.  While the practice of analytically checking your additions is encouraged, and will be discussed throughout the duration of this blog post, please note that sampling procedures and tartaric acid settling time will greatly influence your juice TA after tartaric acid addition.)

A problem for winemakers is that unless potassium uptake and management is addressed in the vineyard, they will likely have to deal with having high potassium-based fruit for several years.  However, winemakers are encouraged to work with their growers, as this is a relatively newer viticultural issue that the Mid-Atlantic is facing, and it may take several years to stabilize before results are seen in incoming fruit from the vineyard.

In regions like Australia, which frequently experience high K concentrations in their fruit and wines, making tartaric acid additions to the juice, pre-fermentation is often recommended to lower the pH of the must/juice and precipitate some of the potassium as it binds to tartaric acid during primary fermentation.  While a 2 g/L of tartaric acid addition to must/juice is a common recommendation for acidulating musts, it may not be enough in order to alter the effects of high potassium concentrations in the fruit.  In these cases, a higher addition rate of tartaric acid, such as 4 – 6 g/L of tartaric acid, may not be out of the question.

It should be noted that must/juice acidification will have chemical and sensory implications to the finished wine.   If the winemaker is aiming to produce a specific style, making large tartaric acid additions pre-fermentation may not be conducive with the desired and finished wine style.  However, when dealing with high potassium issues, and hence, high pH issues, larger tartaric acid additions pre-fermentation seem to be helpful in stabilizing red wine color and improving the flavor of red wines.  For those that would prefer a lower TA (<6.0 g/L tartaric acid), deacidification following malolactic fermentation of red wines is recommended. While there are limitations on deacidification practices, including the degree to which a winemaker can deacidify, this action may help improve mouthfeel and decrease the perception of acidity (sourness) in the finished wine.

Wine Trials at PSU

During the 2015 harvest, our research team confirmed that a couple of our varieties that annually had high pH problems came from sites or locations with high potassium retention in the fruit.  This did not necessarily correlate with high potassium concentrations in the soil.

From our Biglerville (Adams County) research vineyard, our Merlot contained 1,682 mg/L K+ and Cabernet Sauvignon contained 1,668 mg/L K+ in the 2015 growing season.  Both samples were taken from the must and analyzed by atomic absorption analysis at Enartis USA – Vinquiry.

Based on previous research from Somers (1975), both musts were considered high in potassium.  The following (Tables 1 and 2) show additional harvest parameters for our Merlot and Cabernet Sauvignon musts in the 2015 season.

As previous yeast strain selection, malolactic bacteria selection, and standard (2 g/L) tartaric acid addition trials did not seem to improve color stability or flavor of the wines in past harvest years, we took the approach at comparing 3 different tartaric acid addition rates (2 g/L, 4 g/L, and 6 g/L) to the Merlot pre-fermentation and two rates (4 g/L and 5 g/L) of tartaric acid to the Cabernet Sauvignon based on previous recommendations made in the Australian literature.  There were fewer treatments on the Cabernet Sauvignon due to decreased yields in 2015.  Please note that these treatments were not replicated and, therefore, we have not provided any statistical parameters.

For the Merlot, the 2 g/L addition rate of tartaric acid acted as the “control,” as previous years indicated no differences in pH or TA by the end of MLF between wines fermented without tartaric acid added pre-fermentation and a 2 g/L addition treatment.  There was no designated “control” for the Cabernet Sauvignon fermentations.

Table 1: 2015 Pennsylvania Merlot must chemistries in 2015; pH and titratable acidity (TA) were adjusted pre-fermentation (i.e., pre-inoculation) and given at least 3 hours of settling time before inoculation with ICV-GRE yeast


Figure 2: Pre-Fermentation tartaric acid addition (2 g/L, 4 g/L, and 6 g/L) trials to 2015 Merlot must. This image shows the wines during malolactic fermentation. Photo by: Denise M. Gardner

Figure 2: Pre-Fermentation tartaric acid addition (2 g/L, 4 g/L, and 6 g/L) trials to 2015 Merlot must. This image shows the wines during malolactic fermentation. Photo by: Denise M. Gardner

Table 2: 2015 Pennsylvania Cabernet Sauvignon must chemistries in 2015; pH and titratable acidity (TA) were adjusted pre-fermentation (i.e., pre-inoculation) and given at least 3 hours of settling time before inoculation with ICV-GRE yeast


The following table (Table 3) shows the differences in pH and TA for each pre-fermentation tartaric acid addition treatment following primary fermentation and MLF for our Merlot wines in the 2015 vintage year.

Table 3: 2015 Merlot wine chemistries (pH, TA, volatile acidity, and alcohol concentration) post-primary fermentation and post-MLF (fermentation trials were not conducted in replicate)


Trends were similar in the 2015 Cabernet Sauvignon wines, as shown inTable 4.

Table 4: 2015 Cabernet Sauvignon wine chemistries (pH, TA, volatile acidity, and alcohol concentration) post-primary fermentation and post-MLF (fermentation trials were not conducted in replicate)


While we do not quite have an explanation for the rise in TA from post-primary fermentation to post-MLF in the 5 g/L tartaric acid addition treatment in the Cabernet Sauvignon wine, we did note that post-bottling, most of the TA’s slightly decreased across all treatments in both Merlot and Cabernet Sauvignon wines.  A decrease in TA would reduce the perception of sourness even further.  This decrease was likely due to better removal of dissolved carbon dioxide within the wines due to the fact the wines had been moved (i.e., racked, transferred and bottled) more routinely prior to bottling.

The treatments within a varietal were also different sensorially, although this was not quantified.  For example, in the Merlot, the first difference noted was the color.   The Merlot wine that had been treated with 6 g/L tartaric acid had the most vibrant and red-hued color.  The Merlot with a 2 g/L tartaric acid addition had a stronger purple-blue hue.  We did not quantify these differences analytically.  In terms of taste, the 6 g/L tartaric acid treatment had more noticeable and perceptible sourness, but many that tasted the wine agreed that it could be manipulated with some deacidification trials.  The 2 g/L tartaric acid addition treatment tasted flat, had burnt rubber-like flavors and was relatively unappealing.  It did not represent a typical flavor profile associated with Merlot.  The 4 g/L and 6 g/L tartaric acid addition treatments had more noticeable red fruit flavors and less earthy characters.

What should you do in the winery if you think you have high pH wines as a result of high potassium concentrations in your grapes?

  1. Find out if potassium concentrations may be a culprit. Now is the time to find out what you are dealing with.  In a previous blog post, Michela recommended getting petiole samples to determine vine nutrition.  However, you can also test the fruit (must, juice) and the wine for potassium concentrations as well.  We recommend sending your samples to an ISO accredited lab to confirm potassium concentrations in those wines that you believe may be suspect.
  2. Make tartaric acid additions pre-fermentation (pre-inoculation).With very high potassium concentrations, a 4 – 6 g/L addition of tartaric acid pre-fermentation may not be a detriment to wine quality.  However, it is best to know the concentration of potassium you are dealing with before adding up to 6 g/L of tartaric acid pre-fermentation as this can have obvious effects on the wine’s taste and flavor as a finished wine (i.e., make the wine thin or overly sour).
  3. If you are unwilling to test to the potassium concentration, but have a wine with frequent high pH problems during production, use a 4 g/L tartaric acid addition pre-fermentation instead of 2 g/L. The 4 g/L tartaric acid addition rate is a relative “good guess” zone.  Depending on the potassium concentration in your wine, this will either work or it will not work.  If you refer to Tables 3 and 4, we can see that the 4 g/L addition rate was not a bad choice for the Merlot as it resulted in an ideal pH (3.63) and a workable TA (5.96 g/L), but for the Cabernet Sauvignon, the wine resulted in a high pH (>3.70) and a high TA (>6.00 g/L).  This high pH, high TA situation can make the wine both difficult to manage for stability reasons (e.g., making applicable sulfur dioxide additions) while retaining a relatively sour taste.
  4. White wines can also suffer from high potassium. While the content of this blog post has focused on red wines and the effects of color stability and flavor associated with higher pH’s and high potassium concentrations, white wines can also be affected by high potassium concentrations.  In most instances, high potassium can relate to a high pH in the finished wine, which makes the white wine difficult to stabilize or add proper sulfur dioxide additions in order to minimize microbial risk.  Also, many of these wines have low TA’s, giving the white wine a fat, round, or flat mouthfeel (dependent on the variety).  Stylistically, this may not be undesirable, but it is a sensory component that winemakers should be aware of that may occur in these chemical situations.
  5. Alter your pH and sourness post-malolactic fermentation. If the wine tastes too sour for your preference, the time to de-acidify is post-MLF with these wines.  By that time, the color pigments will be fully extracted from the red skins and the flavors will be as optimal as they can be for the variety.  For our Merlot wines, we made additions using (ironically) potassium carbonate, but calcium carbonate can also be used to de-acidify wines.  I usually recommend Patrick Iland’s book for practical information on how to make de-acidification trials in wine. WSU also provides appropriate options and instructions for deacidifying wine.



Mpelasoka, B.S., D.P. Schachtman, M.T. Treeby, and M.R. Thomas. (2003) A review of potassium nutrition in grapevines with special emphasis on berry accumulation. Australian Journal of Grape and Wine Research. 9:154-168.

Somers, T.C. (1975) In search of quality for red wines. Food Technology in Australia. 27:49-56.

Somers, T.C. (1977) A connection between potassium levels in the harvest and relative quality in Australian red wines. Australian Wine, Brewing and Spirit Review. 24:32-34.

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Richard Duckitt – Red Winemaker at Boschendal

Q. When and where were you born ?

“I was born on 24th September 1982 in the Somerset Hospital. However I come from Darling and from a long line of well-known farmers.”

Q. Where did you study and what qualifications do you have ? 

“I studied at Elsenberg doing their diplomas in Cellar Technology and Viticulture.” Then added “That is a great institution and being an Agricultural College  you get to see all manner of agriculture including animal husbandry and so , I believe, their graduates are better all-round farmers/winemakers.”

Q. What was your first job when you left Elsenberg ? 

“Almost across the road with the Melcks at Muratie. That was a great experience  to start your career.”

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

“All winemakers will have similar interests and a basic winemaking foundation, but I am a technical and focussed individual always looking at the little things. I love experimenting and tasting. I also  don’t force any wine into something that it’s not.” Then adds with a grin “If that makes any sense to anyone ! It needs to express itself and I believe in natural freshness and balance.”

Q. How involved do you get in the vineyard ? 

“At Boschendal we have a designated viticulturist, but I venture  into the vineyards  as often as I can and never harvest anything without thorough prior tasting. “

Q. Do you have any varieties you prefer to work with ? 

“Shiraz has always been the top spot, but I am developing a love for Bordeaux varieties. They are definitely more challenging. “ Then adds “I really love a challenge. “ The carries on “ I found that I enjoyed working with cabernet sauvignon when I was in Sonoma, California.  In Spain Tempranillo was good while in Italy Barbera and Nebbiola filled the bill.”

Q. Have you been influenced  by any particular winemaker or region ?

“For us at Boschendal the vineyards and regions play a huge role ! The different styles that the regions deliver has helped build and distinguish our different brands, and I am hugely privileged  to work with so many  different varieties and origins. It is humbling, and also makes me proud to see the variety of styles that our South African terroir can produce. My favourites  seem to come from altitude sites, or cooler coastal vineyards, but I have proved myself wrong on many occasions !” He adds with a grin.

Q. What would you consider your greatest achievement as a winemaker ? 

He answers with seriousness.  “I didn’t become a winemaker foe awards or recognition. For me it is, however,  highly rewarding  to see people just enjoying the wine. To be a skipper of the Boschendal Red wine ship is probably my biggest achievement, and through my whole career I have been working toward this kind of responsibility.”

Q. What “secrets” have you  “developed” that make your wines different to others ?

“The realisation that one cannot fiddle  too much, but gently guide with winemaking intervention. That means harvesting at the correct time, ripe tannins, natural freshness. And no dominating new oak. Also trying new things and seeing what works best for certain areas and varietals.”

Q. How important is modern winemaking equipment in you winemaking ?

“We have a new crusher de-stemmer that makes a huge difference in our Bordeaux varietals  by removing almost all the stalks and green berries. Much more so than conventional machines. I believe in using what works best and if there is new equipment that can have a quality impact we will most certainly look into  it. Saying that we bought a hand cranked basket press this year and it was one of the best buys ever ! So new is not necessarily best.”

Q. What brought you to be the Red winemaker at Boschendal ? 

“Well I grew up on a Duckitt farm in Darling so I am a farmer at heart. I matriculated at SACS and then went to Elsenberg followed by three vintages overseas. The a few locally before spending ten years  at Franschhoek Vineyards. I joined Boschendal in May 2015 as their Red Winemaker.” Then continues in serious vein “As you know Boschendal has been producing great wines for years and have made great strides in the market place so one does not want to change what works or re-invent the wheel, but we constantly look for ways to improve and tweak in pursuit of perfection. We also have some exciting new wines that will be released soon.” Then adds with a mischievous grin “I have been sworn to secrecy so cannot tell you more!”

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We don’t need no education?

“Natural winemaking” is taking South Africa by storm. Whatever that means. The only people who call it “Natural winemaking” are the ones who don’t practice it, which is odd, because generally it’s used condescendingly, as if the “Natural winemakers” are making wine with hemp barrels soothed by the vibrations (that’s an important hippy word) of a moonlit Cape Town Philharmonic Orchestra. It’s also odd because it implies somehow someone else is making wine “unnaturally”, which brings to mind some Nazi-Indiana Jones scene: somewhere deep in a bunker in the Dyatlov Pass, neon blue light bulbs flash on and off in an otherwise darkened room, drums beat,  Robert Parker chants lines from the Necronomicon in baritone and summons a batch of first fill wooded Cabernet from the netherworld – 96 points, should’ve chanted louder or culled a goat for those extra 4 points! Obviously this pertains to the capacity of your imagination, and obviously it’s ludicrous. We both know both camps make excellent and crappy wine.

Now that I have built a wall of preference equity, I shall assert my opinion; today I will take a dig at Natural/Minimal intervention wine. The idea occurred to me in some sort of jolting epiphany. I was trying to memorise the structure of a wood tannin (a taste chemical derived from wood often found in wine), and was struck by a sense of futility. I’ve spent four years learning chemical and biological movements in wine; furthermore, millions of Rands, Euros and Dollars have gone to yeast profiling, wine chemistry and Oenological research. Yet, this minimal intervention movement, whilst not rendering this research and technology useless, certainly makes it seem more like connoisseur’s trivia than practical knowledge. In a perfect scenario, the grapes would arrive healthy, and minus a timely addition of sulphur, all the heavy lifting is done by the microorganisms in the wine (and the vineyard workers who carried the crates).

As an example: your wine is starting to smell cheesy. Stick it in a barrel and let it sit for 12 months. Bob’s your Uncle; the smell blew off. Sure, it’s interesting to know that yeast produces toxic medium-chain fatty acids that smell like feet, but if we don’t even know what yeast species it is, and we’re not going to do anything (interventionally) about it, then who cares?

I suppose this is not an argument against Natural winemaking, but it does slowly seem to be turning into one opposing wine education. Whilst I sit here, I can think of a few winemakers off the top of my head who possess little to no formal wine education. Furthermore, I can think of many well known winemakers who probably use a mild fraction of the oenological knowledge they paid so many “Madibas” for in tertiary education.

It should be noted that my argument is very contextual (which sort of makes it bullet-proof). I think it would only be possible to make wine in this (scientifically) hands off approach in a small scale boutique winery. When the grapes are healthy, space and time are flexible, it’s much easier to make sure things run smoothly and no wine is spoilt. Conversely, as a friend of mine always says, co-op winemakers are the real winemakers, in the literal sense. They handle vast quantities of, often, very poor quality wine, diseased grapes, massive volumes worth millions in damages should spoilage occur.

Basic (and often the best) winemaking is a recipe, with as few ingredients as possible. As much as no one wants to admit they follow a recipe. It is a consumable food product after all, though the calories are about as functional as eating a pile of paper. The more ingredients/faulty ingredients require more background knowledge to handle, but as long as the grapes are good and the facility is well managed, the wine largely makes itself.

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