'Secondary' fermentation?

A famous quote from Kurt Vonnegut from his book Breakfast of Champions sums up the process:

Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast.  They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne.

This scenario actually applies to the end of the fermentation process for making any kind of wine, or any alcoholic beverage for that matter.

The duration of primary fermentation depends on temperature, growth of the yeast culture, and obviously, the sugar content of the must. In general, the primary fermentation takes about a week. At the end, only residual sugar will be left in the wine since the majority was converted into alcohol and carbon dioxide. 

Visibly speaking, the amount of ‘bubbling’ or ‘fizzing’ happening in the fermentation vessel becomes minimal compared to the vigorous primary fermentation stage. The yeast are slowing down, or dying off, as they succumb to the alcohol or lack of nutritive resources. 

Oxygen was essential for yeast propagation during the primary fermentation. However, now that the yeast cells have converted all the sugar, they no longer produce the carbon dioxide blanket to prevent oxidation of the newly made alcohol. Unfortunately, at this marginal potency of alcohol (generally about 10 to 15% for wine) the wine could spoil as the alcohol turns to acetic acid (vinegar).  I will have more on the science (and microbiology – my favourite topic!) of this process in future post.

In some instances, the fermentation finale as it occurs in the air-locked vessel as described in the last winemaking post is referred to as a secondary fermentation.  The purpose of the air-lock is to allow carbon dioxide to escape and to prevent the entry of outside air which is rich in oxygen.

The wine is siphoned off the sludge, known as ‘lees’, that settles to the bottom of the fermentation vessel.  Called 'racking'.  If at all possible, it is best practice to top up your vessel to minimize the level of airspace or ('headspace').  Using a similar wine to the kind you are making ensures that you will not dilute your creation.


The wine generally sits for at least a month at a cooler temperature to allow the vast majority of fine particulate matter to settle out. However, even after this length of time, the wine may still appear cloudy. Additional steps are taken to polish the wine to clarity with organic or inorganic agents that accelerate precipitation.  This process is known as 'fining' and will be the subject of the next winemaking post.

Primary fermentation

So by now, the yeast are well on their way to turning the grape slurry into wine. As they do so, the temperature of the fermentation vessel will begin to rise as the chemical reactions during the fermentation process give off generous amounts of heat.  As for my 120 L of must, featured below, it started at a chilly 15°C and rose to 25°C in a couple days.

In addition, you will begin to see the characteristic ‘fizz’ associated with the release of carbon dioxide.  The pleasant aroma of fruity grape and wine will fill the air.  Your sense of smell is key here.  As the yeast ferment the juice, they require other nutrients and oxygen.  You won’t have to worry too much if you bought juice from a supplier because most of the balancing of nutrients is done for you.  When working from scratch with your own grapes monitoring acidity, dissolved oxygen, nitrogen levels and a whole other suite of factors play a role (so it's not just up to the sugars) to make sure the yeast get the their dietary requirements.  Although the yeast can’t speak, they certainly let you know when they are stressed.  When nutrient starved, they will begin to use other sources of energy and excrete unpleasant smelling byproducts.  For instance if you smell, something resembling ‘rotten eggs’ it is critical that yeast nutrients be added (more on yeast and nutrients later).

When working with grape skins in your must, the floating cap should be punched down into the juice multiple times per day.  'Cap management' prevents the grape skins from drying out and rotting.  In addition, mixing the cap into the liquid extracts tannin and pigments to build body, depth of colour and flavour.  Tannins are astringent tasting chemical compounds found in grape skins, stems and seeds (other fruits that have high tannic content are pomegranates and blueberries – and don’t forget tea, it has lots of tannins too). They are a chemical class called ‘polyphenols’ and have been purported to act as antioxidants.  Tannins are one of many factors that contribute to the ability of a wine to age over prolonged periods.  We’ll revisit tannins in a section regarding how to evaluate and taste wine. 

A grapeskin cap forms over the surface of the must.  It must be 'punched' down a few times per day.  When making white wine, the skins are generally pressed from the must immediately after crushing the grapes.

Each day, a sample of wine from the primary fermentor is removed, measured for its specific gravity, and this value is recorded. Over the course of about a week the specific gravity will approach 1.000 kilograms/liter.  This is the density of water and indicates that almost all the sugar has been converted to alcohol.  Checking the specific gravity each day allows you to monitor the fermentation rate which helps to predict when it will finish. 

With the yeast exhausting the food supply (sugar) and raising the alcohol, a very inhospitable environment is made.  Most of the yeast die off and sink to the bottom of the vessel.  The amount of ‘fizz’ you see begins to diminish and the fermentation is almost complete.  It is now time for the wine to be pressed from its skins (if present) and siphoned off the sludge at the bottom of the vessel.  You are preparing the wine for ‘secondary fermentation’ processes.

Setting up your juice for fermentation, and great tips

Over the course of this article, I’ll show you the ropes of getting the juice fermenting, the mandatory stage for making wine, of course. In addition, I’ll mainly talk about making wine from the standard home winemaking “pasteurized” format (referred to here at http://kevindonato.blogspot.com/2009/12/buying-juice-and-kits-to-make-wine.html), which is generally 23 L (6 US gal) in volume.


1. You will need

• A food grade plastic bucket (at least 30 L capacity) and lid


• A long plastic spoon or paddle, to stir with


• 5 gram yeast sachet (provided in most kits but most can be bought for a dollar if not provided)


• Sanitizer (potassium metabisulfite powder, or food-grade sanitizing powder product such as chloroclean)


• Hydrometer and test jar (see Fig. 1)


• A wine thief


• Measuring cups

Optional items

• Pectic enzyme


• Yeast nutrient broth powder
  
• Plastic or glass gallon jug
  

2. “Cleanliness is next to Godliness”. That’s right, sanitize everything! Organisms of all kinds, including bacteria, moulds, and wild yeast are everywhere and like to coat your equipment in their mucky essence. They would just love to have a bite of your expensive, sugary juice. They will eat their fair share and give you nothing back but stinky odours and most likely turn your batch into vinegar or worse. Get rid of them by washing and soaking your equipment with the sulfite powder (a tablespoon per liter of cool water will be strong enough, a teaspoon of citric acid helps too – try not to inhale the vapours) or alternative product (follow the manufacturer’s directions for dissolving in water).

From a microbiologist's perspective, like my own, sulfites greatly inhibit the growth of these critters so that they won’t be a harm. Rinse everything in copious amounts of clean water and do not let your clean equipment touch uncleanly surfaces. Wash your hands as well, with hand soap.

NOTE: It is best not to use dish soap as it leaves a filmy residue that will make your wine taste just like the detergent you use (“Hey there, care to try my “Sapon Sauvignon 2006?” – yuck!). Do not use liquid bleach (e.g. Javex) as it too can leave a film and impart off flavours (or even poison your guests!). I often use a product called Chloroclean for big washes. It is a chlorinated product that is safe for food processing. It rinses clean from plastic and glass surfaces. Again, rinse everything well.

3. Pour the juice into the large plastic bucket (easy enough). If you bought a kit that is a concentrate, reconstitute the mix by stirring in the rest of the volume using lukewarm water. Example, if you have a kit that has a concentrate volume of 15 L and the kit makes 23 L, add 8 L of water).

4. Rehydrate the yeast culture: In 50 mL (1/4 cup) of warm water (Ideally, 40°C/104°F. I don’t think you would like to wake up from your slumber to an ice cold shower, would you?). Let the yeast sit for 15 minutes and then gently stir.

OPTIONAL: The yeast nutrients mentioned in the list refer to a mixture of carbohydrates, fats, and proteins that supplement yeast growth. Dissolve in warm water according to the manufacturer’s instructions and then add the yeast for rehydration.

5. Wait until the juice is approximately the same temperature, as the yeast solution (i.e. within 10-15 degrees of each other; the juice will warm up in the room while the yeast solution will begin to cool down).6. Pitch the yeast into the juice and stir very well.

*ProStar Tips*:

Remember your gallon jug? Place the rehydrated yeast slurry into the jug and then stir in 2 cups of juice every 30 minutes until the jug is full (or until you get bored) and then stir the mix into the rest of the juice. What this does is help the yeast to “acclimatize” to the new “juicy” environment. They will get used to the temperature changes, acidity, and begin to digest the juices ingredients (especially sugars). Acclimatization gives the yeast population a head-start and gives excellent, no-hassle, results until the fermentation ends. Picture it like you are ‘training’ the yeast cells to do their job exceptionally well before you give them a large task. Would your boss give you responsibility over the company’s biggest jobs right away? Not likely, but they would be glad to have you ‘work your way up’ first. This mixture is called the “yeast starter” and is a technique used by even the most famous winemakers.

Pectic enzyme? This enzyme breaks down pectin (a complex of sugars that are found in jams and jellies). Pectin causes juices (and newly made wines) to haze up and prevent clearing.

7. Remove some juice with your wine thief and place into your hydrometer and test jar. Float the hydrometer in the jar and read off the point at which the surface of the juice meets the meter. Record this value because we’ll use it later! Generally it should read between 1.100 and 1.070.

Believe it or not, you have just started your first ‘primary fermentation’. It is best practice to keep monitoring the specific gravity of your fermenting juice daily. In about 5-7 days the S.G. should reach close to 1.010.

Fig. 1 A hydrometer. See the gradations and numbers along the stem. Simply drop the hydrometer in the juice and it will float or sink depending on how dense the juice is. More sugar causes the meter to rise higher. As the juice ferments, it will sink into the red zone shown here which corresponds to a specific gravity of 1.000.

Buying juice and kits to make wine

With a little more knowledge about your likes and dislikes as far as wine is concerned, you are ready to make your first purchase of juice to make your favourite wines yourself.



Oh boy! Hang on a second! Don’t you start with buying the grapes first? The short answer is, maybe. You see, years ago, the situation was generally like so: Around mid-September a farmer or grape importer/purveyor would simply set up shop in a market for just a few weeks (the importers were like members of my family who would bring crate loads of grapes, delivered by train, to Toronto from California). People would come from all over the neighbourhood to buy cases of grapes of whatever variety they fancied. Generally, the grapes were brought home already crushed by the purveyor’s crusher and placed into pails, skins, stems, seeds and all. A few days would pass and the juice-skin mixture, called the ‘must’, would start to ferment. Then, the whole mish-mash was pressed and all the juice would flow out into a collecting pail for the rest of the fermentation process.

The process was messy, very large scale (it often took 85 pounds of grapes to make two cases, 24, bottles of wine), and generally done outside. In addition, people that bought juice from starting with crushed grapes had to put in the extra effort to extract colour, especially for red wine (more on this later). Over the years, the consumer has gained a few more options to make the process simpler and more friendly so that first-time winemakers can join in the fun.



Now, you can buy the juice from the purveyor already processed. Crushing and pressing is done for you, the colour is all extracted, the yeast is already fermenting away because it lives on the skins of the grapes, and sometimes, a laboratory technician will “balance” the juice to the appropriate acidity and sugar content to make great wine. This is known as a “fresh juice format” because the yeast has already started working to convert sugar into alcohol and carbon dioxide (the source of the characteristic “fizz” you see). This is a great format for those that don’t want to deal with the mess of pressing grapes. However, I wouldn’t recommend it for a beginner because the juice has to be worked with right away and hence, won’t wait for you to take a workday off so you can tend to it. Generally, the juice is stored in large fridges to slow the fermentation process until the customer is ready to buy it. There are also even simpler options for the beginner.



If you want the juice to sit around ‘silent’ until you are ready. The “pasteurized” or “wine-kit” format is the right one for you. In this format, the juice is made just like the above fresh format but is flash heated. This “pasteurization” is intended to kill (or at least stun) the yeast living inside the juice. These formats generally come with all the instructions you need to make good wine and come with all the ingredients you may want along the way. Most important of these ingredients is the yeast culture that you’ll add back into the juice when you are ready. Because they aren’t actually fermenting when you purchase them, these juices can be kept at room temperature and can be made into wine at any time of year.
Even more exciting is the fact that you can buy pasteurized juices from grapes sourced internationally.



After my first (and botched) attempt at making wine from crushed grapes, I swallowed my pride and opted for a wine kit. It’s the best place to start and you’ll almost never run into any rude surprises along the way.



What about the price? It’s the same concept as buying anything at all – you pay more for convenience. Pasteurized formats cost anywhere between $60-$150 (yielding 30 bottles of wine, and higher quality generally commands a higher price), while pressed juice ranges from $35-90 (also making 30 bottles) and the price is just a tad cheaper when buying a corresponding amount of grapes.



The entire process to make wine from a kit lasts 4-8 weeks, depending on its quality. In addition, these wines generally benefit from aging, from a month to a year, before enjoying them.

Fall 2008: I enlisted the help of my best friend Nader (left) for this batch. Over 250 litres of Cabernet Sauvignon, Merlot and Cabernet Franc juice and 100 pounds of skins went into the drums behind us.

Here we are, you’ve learned about your tastes in wine, decided on a format you wish to purchase and now the work (fun) begins!

Grapes to wine in five minutes

If someone has any ideas on how to make grapes turn into decent wine in five minutes please let me know, because I’ll start some high-throughput, large-scale production and we’ll become rich beyond our wildest dreams. Rather, the five minutes I’m talking about is how I’ll briefly describe how wine is made.

First, we start with the newly picked grapes (but also be aware that it takes an entire year of work, a great deal of patience, and luck from mother nature to get a mature grapevine to produce quality grapes). In a production facility the grapes are lightly broken apart to let the sugary juice drain out. The whole mash is placed into large open vats. For those that like white wine, the juice almost never sees the skins of the grapes again and is pressed out and saved. For red wine, the juice will bathe in the skins from a few days to even a month depending on how much of the red colour needs to be extracted from the skins.

When the grapes have been broken apart the juice is exposed to the most important player, the yeast. These little critters are met with a foray of sugars to eat. They mingle, have a great big party, and over one to two weeks will turn the majority of that sugar into alcohol – what we know as fermentation. As they do this, they produce the carbon dioxide that gives the characteristic fizz and foam that helps to preserve the newly made wine. This “primary” fermentation lasts for about a week and converts almost all the sugar into alcohol. It is also at this point that red wines are pressed from the skins.

By the time the stage is complete most of the yeast have died off (when they party way too hard and have nothing left to eat they succumb to the alcohol) and sink to the bottom of the vat. The new wine is siphoned off and then placed into a new vessel with a special one way valve to lock off the air and prevent spoiling. There are still a few yeast partygoers that manage to stick it out and stay for an afterparty. This “secondary” stage of fermentation allows these yeasts to ferment the rest of the sugar and the process can go on for weeks. In more advanced techniques, the “secondary” fermentation actually refers to a stage where special bacteria are added to the wine. Rather than make ethanol, these bacteria convert a certain type of acid in the wine that tastes very ‘tart’ into an acid that we perceive as ‘smooth and round’.

When all the fermenting is complete, the wine can be left in a cooler environment to clear itself of the rest of any suspended sediment. After, the wine can be either filtered and bottled right away, or left to “age” in an oak barrel or other container for months to years before bottling.

Now the winemaking is complete, you can uncork the bottle and enjoy – just try not to finish it all in five minutes.

One of the key components of this blog will be to describe in further detail how great wine is made. The amazing thing about this process is that there are so many variables that will affect overall quality of the wine, and each represents a stage in which you can 'customize' the wine to reflect your personal tastes.