Once grapes have arrived at the winery, they are processed in preparation for fermentation. White grape varieties are typically fermented without skins, while red varieties are typically fermented with skins. Either way, a winemaker needs to ensure that the yeast have a happy environment for a successful fermentation and there are several components to keep in mind.
is often considered the most important pre-fermentation characteristic in wine production. Alcohol is produced by the conversion of sugar by yeast during fermentation (1° brix equates to approximately 0.55% v/v alcohol), so typical brix levels prior to fermentation vary greatly depending on stylistic choices made by the winemaker (of course, harvest conditions can lead to some crazy brix levels; way too low to way too high). Every country has its own laws regarding whether water can be added (to decrease sugar levels) or sugar can be added (to increase sugar levels) prior to fermentation, which gives winemakers a little bit of room to play depending on where the wine is being made and where the wine is being sold. Fermenting wine to dryness (less than 2 g/L residual sugar, which is particularly desired for still wine production) is often difficult when there is too much sugar; many yeasts are subject to sugar toxicity levels and alcohol toxicity levels, which is why many commercial yeast producers offer high-brix yeast (they can start ferment with lots of sugar and finish ferment with lots of alcohol).
pH and Acidity
The balance between pH and acidity level is an important indicator of ripeness prior to harvest, used in conjunction with brix levels and sensory evaluation, to determine the best picking dates. Once in the winery, pH and acidity play a major role in winemaking.
Titratable acidity, also referred to as total acidity, is the combined measurement of all acids in a juice/must/wine presented as grams per liter (g/L). There are several different acids present in grapes and wine, but tartaric and malic acids are found in the highest concentrations. Different grape varieties are predisposed to have higher concentrations of one or the other, though environmental factors play a major role. Usually, titratable acidity levels fall between 6-10 g/L prior to fermentation, largely dependent on things such as grape variety and wine style. A winemaker will usually desire higher acid levels for wines destined for malolactic fermentation and even more for those earmarked for sparkling wines.
Most winemakers would likely argue pH carries more importance than titratable acidity. Why? pH has a major effect on microorganisms present. Yeasts require juice/must within a certain pH range to perform non-stressful fermentation. This range is dependent on the specific strain, but usually is somewhere between 3.1 and 3.8 pH. A major issue for winemakers are undesirable microorganisms, many of which can also thrive in this pH range.
There are different regulations for the types and amount of additives a winemaker can use to adjust pH and acidity. Tartaric acid is the overwhelmingly favorite for increasing acidity and therefore decreasing pH. Potassium carbonate is commonly used for decreasing acid, though it has little effect on pH levels.
Managing oxygen levels in wine is a major topic in the modern wine industry. Research continues to show that slight variations in oxygen throughout the winemaking process can have significant effects on wine quality. Nevertheless, oxygen is often left unmentioned when discussing fermentation, one of the stages its levels are most important.
Yeasts are facultative microorganisms, capable of conducting aerobic and anaerobic respiration depending on environmental conditions. Supplying wine yeast with adequate levels of oxygen during the stationary and growth phases is essential for a successful fermentation. Research shows that yeast propagated aerobically contain a higher proportion of unsaturated fatty acids and significantly more steroids than those anaerobically propagated, translating to higher yeast viability.
nce fermentation is underway, consumption of oxygen and subsequent production of carbon dioxide quickly removes oxygen present in the juice/must. In most circumstances, this is desired (not during yeast propagation activities). Oxygen may be added during fermentation of somered varieties. It is sometimes induced as a method of removing carbon dioxide, which becomes toxic to yeast above 0.2 atm concentration.
Yeast cells require several different micro-nutrients during the growth phase, including nitrogen-containing compounds, vitamins, sterols, and minerals. The extent of nutrient requirement is largely based on the amount of sugar the yeast will need to consume and convert to alcohol. The higher the juice/must brix prior to fermentation, the more nutrients the yeast will require. Yeast-assimilable nitrogen (YAN) is a measurement showing the quantity of ammonium salts (NH4+) and free alpha-amino acids (FAN) that are available in the juice/must for yeast consumption.
Proprietary nutrient products are available from several different wine additive companies. Some are specifically designed for use during yeast rehydration, while others are designed for use during fermentation. Diammonium phosphate (DAP) is additive for increasing nitrogen, though varying opinions on its effectiveness exist. Many winemakers use routine rates for nutrient additions, but this can also lead to ‘too much of a good thing’ situation. Read Yeast Rehydration Nutrients and Fermentation Nutrients for more info.
Most people probably don’t realize that sulfur dioxide is a naturally occurring compound in grapes, but it is a very important additive for most winemakers. Sulfur dioxide is added to help protect juice/must/wine against oxidation and spoilage.
Balancing adequate levels of sulfur dioxide to inhibit undesirable microorganisms while allowing desirable yeast to remain active is essential. Prior to fermentation, a good baseline recommendation for free sulfur dioxide is less than 10 ppm and less than 50 ppm for bound sulfur dioxide. These levels can vary widely depending on factors including yeast strain, juice/must pH, presence of infection in the juice/must, and processing considerations. The winemaker’s stylistic choices also play a part; for instance, sulfur dioxide helps retain fresh fruit characteristics in white wines.
Just like with pH, yeast have an ideal temperature range in which they are most likely to successfully ferment within. Too low or too high of temperature will stress yeast. Since fermentation produces heat, it’s usually a good idea to begin fermentation at a slightly lower temperature than desired.
Winemakers have varied opinions on ideal temperatures dependent on the grape variety, grape quality, and wine style. White grape varieties are typically fermented between 54-63° F (12-17° C), while red varieties will commonly be fermented at higher temperatures upwards of 80° F (26° C).
Q. Where were you born ?
“I was born in Robertson on 1st April 1991.”
Q. Do you get teased about being born on 1st April ?
The answer comes with that charming , trade mark grin. “There was a time I was constantly teased about being an April Fool but I think I have proved otherwise !”
Q. Where did you study ?
“I went to Elsenburg and received my bachelor’s degree in Oenology and Viticulture.”
Q, Do you consider your approach to winemaking to be different to others ?
“Not really. There is only so much that you can do with wine. I do think winemakers distinguish themselves from other winemakers by the way he or she pays attention to the finer detail. I’m a strong believer in doing the ten small things perfectly.”
Q. How involved do you get in the vineyard ?
All of a sudden, very serious. “The truth be told, not enough. If I get a chance to see what the vineyard team is busy with, I’ll take it but unfortunately it happens seldom. The cellar keeps me really busy but it id definitely on my priority list to get out more.”
Q. Do you have any varieties that you prefer to work with ?
“At this stage, not really. What I really love about Bon Courage is the opportunity to work with a big variety of cultivars from MCC, Desset wines, Dry white and reds and even Mampoer !” Then continues “We have a big collection of cultivars on the farm so I’m patiently trying to see what each vineyard block has to offer. So far I’m really spoiled with great vineyards with amazing character. It makes it difficult to pick a favourite, but eventually I will have to narrow it down. I don’t want to look like a jack of all trades but master of none.”
Q. Have you been influenced by any particular winemaker or region ?
“Winemaker – yes. Wine region – not at this stage. I think every wine region can make any type of wine and has something unique to offer. Lourens van der Westhuizen , winemaker at Arensig Winery, once described it correctly saying we have so many terroir pockets, for instance, Robertson. Pockets where you find ideal climate for whichever cultivar you want to grow. I also admire Charles Hopkins at DFe Grendel for his attention to detail and Bartho Eksteen for his originality. Not to mention Jacques at Oom Andre Bruwer of Bon Courage.”
Q. What would you consider your greatest achievement as a winemaker ?
With a great deal of modesty. “ I am still young, my hall of fame is pretty empty, but luckily last year I was in the right place at the right time and I received the Diner’s Club Young Winemaker of the Year award and only then realised what a big deal it was. I can honestly say after that night I do know how it feels to be in the life of Brad Pitt for one day with all the cameras flicking !! “
Q. What “secrets” have you “developed” that make our wines different to others ?
“I would not really say “secrets” but one of the main aspects that probably differentiate one from another is how well you manage to extract your varietal’s character for that specific vineyard and to balance it out with the correct oak. I do think it is very important to use the right oak with the right varietal and also to determine the right amount of it. I personally love to smell the vineyard in the wine and believe that oak must be used carefully and only to add some complexity to the wine.”
Q. How important is modern winemaking equipment in your winemaking ?
“Technology has made our lives much easier, especially when you harvest a few hundred tonnes. The two types of machinery which I am most thankful for is probably a destemmer and a wine pump, without those two you can still manage. I also have to admit I still enjoy a good old punch down. I like to see it as an early morning gym session and have a good work out !! During modern winemaking you still tend to go back to the old ways for instance picking by hand ! I like using a mixture of the two worlds.”
Q. What of the future ?
“ I grew up in Robertson with a typical countryside living style where everyone knows everybody. It is a friendly town where the majority still greet each other in the town. My parents farm about 4 km from Bon Courage and I am spoiled to still enjoy daily lunch with my parents. If Robertson should ever host a master chef competition my mother would , without doubt, be the champion !” In a different tack “After school I got the opportunity to go to Johannesburg for a year to play rugby and became a full blooded Lions rugby supporter. I then returned to the Cape to go to Elsenburg where I received a great education. I had a very influential lecturer in the form of Lorraine Geldenhuys. After that I did few vintages overseas.” “My main challenge is to get to know the vineyards I am working with. I am very pleased with the 2016 reds and I can’t wait to see the process through.”
People that are close to me will know that there is one more thing that I am positively passionate about besides wine, and that is music. I myself cannot play an instrument (to any extent worth mentioning), just like I cannot make my own wine (to any extent at all). So I had to think that there must be a link between these two disciplines if they both spark my intrigue so much.
I started my search on the world wide web to try and see if anyone else has found the missing link. Turns out, there are quite a few musicians and artists that have the same obsession that I have. So much so that they have written songs about their love for wine! Legendary blues artist Stevie Ray Vaughn once sang “Well I love my baby like the finest wine / Stick with her until the end of time”. Ok, so maybe the song isn’t about his love for wine, but he loves his wine just as much as his lady- which I think is saying quite a lot. And then I think back to my childhood days singing ‘Tiny Bubbles’ by Don Ho while splashing around in the bathtub- how was I supposed to know that the whole song is about Champagne? Even Jay-Z is educating the “youth of today” about Bordeaux and Burgandies (in a slightly unorthodox way) with his song ‘Tom Ford’.
I have also only recently come to realise what an influence the music that is played in a tasting room has on the overall wine experience. We all know that music is a great way to improve the so-called atmosphere, but by playing the right kind, it can help to awaken all the senses- including your taste buds. And it is enhanced even more if the music is performed live. Sure, most tasting centres opt for the very predictable smooth jazz or ever-pleasing slow blues (both of which I personally enjoy and it certainly does work), but I believe that with a little creativity it would even be possible to “pair” music and wine. Just think how your senses might be tingled when you listen to some soft pop whilst sipping on your Pinot gris, or maybe open a bottle of your favourite Chardonnay next time you turn on the stereo to listen to some Chopin- you might just like the wine even more than before.
My personal favourite music & wine combination intertwines two things that are very dear to my heart- Shiraz and rock n’ roll. Some might say that wine is not really a “rock n’ roll drink” and might even prefer whisky or gin, but nothing says hard-core, in-your-face flavour like a strong, snaring Shiraz. The bold, ballsy taste that is left in your mouth after a good glass full is nothing short of a Mick Jagger dance move. And if you are lucky enough to enjoy that glass full whilst you are listening to some Led Zeppelin, you will be sure to find yourself ascending the ‘Stairway to Heaven’.
Whether you like rock, pop, classical or R&B; Shiraz, Pinotage, Chenin or Chardonnay- I am sure there is a music and wine combination out there that will get your foot tapping and your taste buds tingling.
Article by Becca Yeamans of ‘The Academic Wino’
How a wine tastes is dependent upon many factors, including (but not limited to) the variety, the vintage, where the grapes are grown (soil, climate, etc), as well as the viticultural and winemaking techniques employed during processing. The compounds responsible for how wine tastes are known as free volatile compounds, as well as aromatic precursors, the latter of which are present at much higher concentrations. Non-volatile sugar-bound conjugates (a.k.a. “glycosidic compounds) have been well studied and have been shown to be released over time during wine aging or by using specific winemaking techniques. Specific glycosidic compounds known to be released over time, thus affecting how a wine develops and tastes, include terpenes, C13 norisoprenoids, benzenic derivatives, volatile phenols, and C6 compounds. All of these glycosidic compounds have low odor thresholds, thus requiring very little to elicit a sensory response.
While wine aromatics have been extensively studied, it is not well known exactly how compounds responsible for aromatic character in wines interact with the physiological make-up of the human mouth. In addition to environmental and chemical sources, it is possible that the perception of different wine aromas can be altered by physiological factors like mouth temperature, saliva composition, or the oral microbial community present in each individuals’ mouths. Studies focusing on onions, bell peppers, and grapes found that the microbial community in the human mouth hydrolyzed odorless compounds into their corresponding volatile aromatic compounds, giving reason to believe something similar could potentially happen with wine. Perhaps the microbiota living in the human mouth can hydrolyze these odorless precursors and convert them into their corresponding aromatic compounds, just like it’s been shown with other foods.
A 2015 study in the journal Food Chemistry aimed to evaluate whether or not human oral microbiota can convert odorless aromatic precursor compounds in wine into their corresponding aromatic glycosidic compounds. The results could potentially have a profound impact on our understanding of how we taste and evaluate wines.
Experiment 1: In vitro
For the in vitro experiments, three microbes commonly found in the human mouth were cultured on sterile growth media. Different concentrations of grape extract were added to the microbes, with bacteria growth measured after 24-48 hours, depending upon the specific microbe. From these growth measurements, inhibition of growth was also calculated.
Experiment 2: Ex vivo:
For the ex vivo experiments, fresh saliva was collected from three volunteers (ages 28-31). Prior to collection, the volunteers had not taken any antibiotics or other medications, and were non-smokers. Volunteers did not consume any food or beverages within two hours of the saliva collection time.
The saliva from each volunteer was divided up into four different treatments: 1) fresh saliva in an aerobic culture, 2) fresh saliva in an anaerobic culture, 3) sterilized saliva (pasteurized), and 4) non-enzymatic saliva (heated). Microbe counts were measured after 24-48 hours at 37oC.
Grape extract (comparable to 40g of grapes) was added to the saliva cultures and bacterial growth was monitored. Glycoside hydrolysis by the microbes was measured by monitoring and analyzing the volatile compounds released after four time periods (0hr, 2hr, 24hr, and 72hr).
To test the ability of human oral microbiota to hydrolyze glycosidic compounds in general, a standard solution of octyl-β-D-glucopyranoside was cultured with the saliva samples and monitored over time.
- No human oral microbiota was found in the sterile or non-enzymatic saliva treatments (as expected).
- Adding octyl-β-D-glucopyranoside to human saliva resulted in hydrolysis and the release of the volatile compound aglycone.
- None of the oral microbes were inhibited by the glycosidic extract.
- Every oral microbe tested was able to hydrolyze the glycosidic compounds in the grape extract, resulting in the release of terpenes, benzenic derivatives, and C6 alcohols.
- Note: Many of these compounds can be associated with various aromatic characteristics in wines (e.g. terpenes can produce flowery or citrus aromas and certain benzenic compounds such as β-phenylethanol can produce rose aromas.)
- While some aromatic compounds were found as a result of the oral microbes hydrolyzing the glycosidic compounds in the grape extract, other common compounds were not present (i.e. C-13 norisoprenoids, vanillins, and volatile phenols).
- The ability to hydrolyze and the resulting aromatic compounds produced from this hydrolysis depended upon the type of oral microbe present.
- A. naeslundii was the producer of the most linalool and its oxides, which is associated with floral notes in grapes and wine.
- E. faecalis, A. naeslundii, and S. mutans produced the most aroma-causing aglycones.
- G. adiascens, V. dispar, and F. nucleatum produced the fewest aroma-causing aglycones.
- NOTE: Some of these bacteria have difficulty growing in culture media, so it isn’t clear whether their lack of glycosidic hydrolysis is real or a function of being unable to grow under the experimental conditions.
- There were significant differences between the three volunteers in terms of the species make up of their mouths. No person had the same species in the same amounts.
- While the microbial counts were statistically the same for each volunteer, the aromatic aglycones produced were significantly different, which is likely due to the different species present in each individual’s mouth.
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Q. Where were you born ?
Q. Where did you study and what qualifications did you acquire ?
“ I did I B.Sc Agric (viticulture and oenology) at University of Stellenbosch. Graduating in 2000. The I did a Post Graduate Diploma in Management practices specialising in Wine Business Management at University of Cape Town Graduate School of Business and graduating at end of 2015.”
Q. Do you consider your approach different to others ?
“No ! But like most young South African winemakers, with great dedication.”
Q. How involved do you get in the vineyard ?
“Every day. It is just part of what a winemaker must do.”
Q. Do you have any varieties you prefer to work with ?
“Shiraz. So Allesverloren is just perfect for me.”
Q. Have you been influenced by any particular winemaker or by a wine region ?
“No. However, being here at Allesverloren the Malan influence has it’s effect ! ”
Q. What would you consider your greatest achievement as a winemaker ?
“Being able to make strong strategic moves in the cellar and in my duties on the estate in field of marketing. “
Q. What “secrets” have you “developed” that make your wines different to others ?
“I do not have any secrets.”
Q. How important is modern winemaking equipment in your winemaking ?
“It is important to have a good balance between old and new. At the end of the day one still needs to make a profit.”
Q. Are you the first Non-Malan to be winemaker at Allesverloren ?
“ There were Assistant winemakers before me but I am the first to have the title of Manager/Winemaker. So one can say that I am the first “non-Malan” winemaker but for overall marketing Danie Malan is still the man. Also, after all the many years of Malan influence at Allesverloren things don’t just change !”
Q. You say “many years”. How many years have the Malans been involved ?
“Daniel Francois Malan arrived from Wellington in 1870 to take over the farm which was considered to be all lost after a raid by the San people. Slowly but surely he put the farm in order. In 1945 the farm was divided between two sons and the one who got the portion with the old farmstead began making wine specialising in Port style wines.”
Q. Now days you make a lot of non-port style wines ?
“As the demand for port declined the port varieties were used for dry red wines and other varieties were planted hence the Allesverloren Cabernet sauvignon.” He continued “We also make a fortified muscadel but you will see the strong influence of port in our Touriga Nacianal dry red and Tinta Rose.” “We are also famous for our Shiraz.”
Q. What of the future ?
“I believe it will be possible to get more South Africans to enjoy wine. We must all stop being so snobbish about wine, then people with no wine knowledge will feel more comfortable to drink wine .”
Q. Do you have any idea how to do this ?
“We are doing our best by providing a beautiful venue at the foot of the Kasteelberg for weddings and functions. Here people can drink wine while eating good Swartland food in the most glorious surroundings.”
Q. When you were studying at Stellenbosch did you ever think you would manage such an estate ?
“No way but I will still be fully involved with winemaking and set on my goal to get more people enjoying our great South African wines.”