Recently, I was lucky enough to be gifted a wine-making kit, from my grandfather. Being a winemaking student, I couldn’t fight off the excitement and curiosity to give garage-fermenting a bash. Before getting too excited and starting this home-ferment experiment, I would strongly recommend doing a little bit of research.
After making wine in a cellar, the poor wine-kit’s instruction manual was subjected to a lot of scrutiny from my side. For start, what appeared to be a rather fun and easy task turned out to be a lot more complicated than I had hoped it would be. After consulting with my ‘Yeast Prof’, ‘MLF Prof” and ‘Wine Prof’, we had concluded that, for the sake of producing a drinkable wine, I would have to deviate from the wine-kit’s original instructions. Topping up my Shiraz reserve with water on a regular basis just wasn’t going to cut it for this young lady!
A few helpful tips to keep in mind when attempting a home ferment, regardless of what the bizarre instruction manual recommends: The instruction manual will tell you to thoroughly read and follow instructions; do not fall for this trickery! If you are uncertain about something, I would definitely suggest asking someone in the industry for their opinion, if you are new to the winemaking-game and are using the kit as your first attempt at making wine, don’t hesitate to ask Google.
Using a beer kit fermenter is recommended, it is easy to clean, store and already comes with a fermentation/bubble cap. Winter is the perfect time of the year to use your garage as a type of cold room for a white wine fermentation, the cooler temperatures act as a natural and more cost-effective cooling system for your fermenter. In summer, I think red wine would be a better option due to the much warmer and more ideal temperatures.
The kit I have strongly suggests (they tell you…) that you rack your wine a few days after inoculation. They reason that this is due to the secondary fermentation that should occur straight after fermentation, yet they supply consumers with no malolactic-bacteria and the Shiraz reserve is pasteurized. It is also said that one should rack again after an additional 10 days, a full secondary fermentation/MLF in 10 days? – A winemaker’s dream! I would therefore skip this step altogether, this also lowers the risk of oxidation inside your fermenter and increases the palatability of the final product.
During the garage winemaking process, I would also suggest that you collect as many empty wine bottles as possible. It isn’t necessary to buy new bottles, as you can sanitise the used ones before filling and sealing them with a cork. Corks can be sourced online and are also fairly inexpensive. If you prefer beer to wine, fear not, you can also use beer bottles and screw caps. These offer a perfectly sized portion of wine (2 glasses) and can be enjoyed chilled, straight out of the bottle! If using screw caps, it is important to remember that wine can continue fermenting in the bottle, even if fermentation appears to be complete, for this reason I would suggest that you drink the wine as soon as possible.
It is incredibly difficult to produce a faultless wine from one of these kits, due to the constant risk of contamination as well as a higher oxidation risk. It is my personal belief that any garage winemaker that can produce a drinkable final product, should consider furthering their skills by taking a winemaking course or making wine in a cellar. If your wine isn’t drinkable, remember that you can always cook with it instead!
Garage winemaking is incredibly fun but unfortunately falls short in comparison to the cellar. There is nothing quite as exciting as hand selecting your grapes and being elbow deep in fermenting skins and juice doing punchdowns.
After my first harvest, I quickly learned to stop apologising to every winemaker I met for my tannin and red-wine stained hands, mostly because everyone else’s hands looked exactly the same! Feeling small berries burst as you push down on the crush-cake in the basket press and watching deep purple droplets splatter out against your ‘harvest jeans’ cannot be replaced by diluting grape must in your garage.
It is also a lot easier to control the wine and fermentation process in a cellar, with Carbon Dioxide tanks at the ready to combat oxidation, and temperature regulated tanks to ensure optimal fermentation conditions, it’s hard to go wrong. Winemaking is by no means an easy task, you are constantly kept on your toes and have to watch your wines like a parent watches a pre-schooler with a pair of scissors – on high alert and ready to pounce if something goes wrong.
I don’t think anything can quite compare to the anticipation of popping the bung on an oak barrel, religiously checking up on your wines and watching them improve weekly. Wood chips in a plastic fermenter just aren’t the same. If you are a wine enthusiast, a wine drinker or even just perhaps a curious bystander, the garage wine-kit can be a very exciting and new process to try. If you are a winemaker, it may be a bit difficult to overlook the minor things like, “do not rehydrate the yeast” or “leave an air gap of about 1 litre”, but I would like to encourage and challenge you to give it a go. Even if the final product isn’t amazing, it is still a very entertaining and enjoyable experiment!
by Natasha Pretorius, Lynn Engelbrecht & Maret du Toit – Wineland Media
Various factors influence the amount of diacetyl, acetoin and 2,3-butanediol produced during fermentation impacting the buttery aroma.
Malolactic fermentation (MLF) is a secondary fermentation carried out by lactic acid bacteria (LAB). This process can occur spontaneously or can be induced by using MLF starter cultures. Currently, the commercially available MLF starter cultures belong to the species Oenococcus oeni and Lactobacillus plantarum. The use of starter cultures to induce MLF is preferred to avoid the risks associated with spontaneous MLF. The starter cultures can be inoculated simultaneously with the yeast, known as co-inoculation, or after the completion of alcoholic fermentation, known as sequential inoculation. MLF is a desirable process as the decarboxylation of l-malic acid to l-lactic acid and carbon dioxide decreases the acidity and increases the microbial stability of wine. This process also influences the organoleptic properties of wine.
In addition to malic acid, some MLF starter cultures can also degrade citric acid usually present in grape must at concentrations of 0.031 g/ℓ to 0.42 g/ℓ. The metabolism of citric acid leads to the production of acetate, d-lactate, diacetyl, acetoin and 2,3-butanediol (Figure 1). The production of acetate is one of the reasons for the 0.1 g/ℓ to 0.3 g/ℓ volatile acidity increase during MLF as citric acid metabolism is linked to malic acid degradation.
When present at low concentrations, diacetyl can contribute to the complexity of wine. Diacetyl has a buttery aroma which contributes to wine complexity when present at concentrations above its sensory threshold value of 0.2 mg/ℓ to 2.8 mg/ℓ. However, high diacetyl concentrations above 5 mg/ℓ can give rise to an overwhelming buttery aroma that masks the fruity and/or vegetative aromas in wines. Diacetyl can be reduced to the less sensory active acetoin and 2,3-butanediol (Figure 1) with much higher sensory thresholds of 150 mg/ℓ and 600 mg/ℓ, respectively. The reduction of diacetyl to these compounds is therefore encouraged during winemaking if a buttery style wine is not wanted. Several factors influence this reduction, as well as the sensory perception of diacetyl in wines.
A few of these factors include:
Composition of grape must
The grape must composition influences the concentrations, as well as the sensory perception of diacetyl. There are three main components of grape must that can influence the diacetyl concentrations during fermentation. These components are:
Diacetyl is more rapidly reduced to acetoin during the fermentation of grapes from warm climate regions that have a higher pH. Wines from these regions might therefore have less diacetyl than wines from cool climate regions that are usually associated with a low pH.
- Citric acid concentration
Grape must with a higher citric acid concentration leads to increasing concentrations of acetate, d-lactate, diacetyl, acetoin and 2,3-butanediol. Excess acetate and d-lactate causes over acidification and inhibits bacterial growth thus prolonging MLF. A longer MLF duration can result in more diacetyl being produced during the fermentation.
Several studies have previously indicated that diacetyl in white wines was less stable and more likely to be reduced to acetoin and 2,3-butanediol than in red wines. However, the buttery aroma of diacetyl is more likely to occur in white wines than in red wines, due to the presence of phenolic compounds such as p-coumaric, caffeic, ferulic, gallic and protocatechuic acid. These phenolic compounds lower the buttery aroma in red wines by binding to diacetyl.
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