This is a summary based on the work by: Aurelie Saglio et al. (2018). All images and figures below belong to the authors.
Their hypothesis: “…hot ganache is an oil-in-water emulsion. Non-fat cocoa particles influence emulsion stability, though how is not clear. Upon cooling, cocoa butter crystallises and partial coalescence takes place between fat globules. Therefore, crystallised ganache is more a bicontinuous system tan simple emulsion.”
The authors also looked at how the microstructure of the ganache (what happens under the microscope) reflects the observable behaviour we see when making a ganache.
Let’s begin. What is ganache?
Basically, from a non scientific perspective, it is chocolate mixed with a water-based liquid. This liquid is often cream, but can also be juice, milk, water, nut milk, and the list goes on. Chefs are becoming quite creative these days!
The soft centre of a chocolate truffle or bonbon is often a ganache. For instance, a raspberry ganache will include chocolate (either dark, milk, or white), cream, and raspberry puree. Some chefs may add some extras such as butter, and maybe even alcohol such as rum.
Ganache was invented in France in the 1850’s, when water was accidentally poured over chocolate. Chocolate is hydrophobic due to its high fat content. A small amount of water added to chocolate will cause it to seize and become thick and grainy looking. However, with the right proportions of water to chocolate, that thick grainy mess can become a smooth silky ganache.
How do we define a ganache?
There is no universal standard or legislation that defines what a ganache is or isn’t. The water aspect can come from many sources as stated above, and one can use dark, milk, or white chocolate. It can be very runny or very thick. However, we can understand it from a more scientific perspective.
Saglio et al. suggests that ganache is in an oil-in-water emulsion. This means that little oil droplets (the fat phase) is evenly dispersed within the aqueous water phase (such as cream). Contrast this to a fatty margarine, which is the opposite: water droplets (aqueous phase) dispersed within a fat matrix.
To get an idea of what this means visually, here is an image of a standard emulsified ganache and a split ganache.
Chocolate is made up of a fat phase (the cocoa butter), and within it is a suspension of sugar and cocoa particles. These sugar and cocoa particles are contained within this fat phase of cocoa fat.
Cream, on the other hand, is another oil in water emulsion made up of a tiny milk fat and proteins suspended in a liquid water phase.
Ganache is a mixture of fatty chocolate chocolate suspended in a water based cream. If the proportions and method of combining are optimal, a emulsified standard ganache will be formed (Figure 1 a.). If the proportions are off, the ganache will appear “split” (the emulsion is broken) and it will appear thicker and greasy (Figure 1 b.).
Microstructure of Ganache
Emulsified liquid ganache
In Figure 2a you can see a real microscopic image of a liquid emulsified ganache (or “standard” ganache as the authors put it). The green dots are tiny fat droplets dispersed in the aqueous phase. They are more or less evenly distributed, and kept apart from each other because there is enough water in the ganache for them to be dispersed.
Bicontinuous Crystalised ganache
As the ganache in Figure 2a cools and crystalizes, what was an emulsion becomes a bicontinuous system (2b). The tiny green droplets stay put, but as they crystalized, they are linked with fat “bridges” between them. This is not coalescence as in a split ganache. They are still evenly distributed in the aqueous phase, but connected to one another into a bicontinuous fat network.
Split crystalized ganache
It’s a little more difficult to see, but in Figure 2 c. the green fat has coalesced into large areas and crystalized, instead of staying put and building bridges as in Figure 2 b. In this case, the ganache will feel more gritty in the mouth, since these large fat crystals of cocoa butter have hardened into little chunks, rather than remain as small tiny pockets as in figure 2 b. This is not a bicontinuous network of fat, but rather just a amalgamation of the fat into large droplets that harden as they cool.
The components of ganache and their role:
Here we will go through the components of a simple dark chocolate ganache as discussed by the authors. This ganache includes dark chocolate, cream, and butter.
Components of the ingredients:
Dark chocolate contains: cocoa butter, cocoa solids, sugar crystals
Cream contains: water, milk fat, milk proteins
Butter contains: milk fat, milk proteins, some water
Components of the Ganache
Cocoa butter: Cocoa butter is often the main fat component within the ganache. It is crucial that these fat droplets remain under 20 microns and are evenly dispersed throughout the water phase of the ganache, which in this case is the cream.
Milk fats: These come from the cream and the butter. These are already disperse in the aqueous phase of the cream.
The more fat contained in a ganache, the thicker it will become. A ganache with a higher ratio of chocolate to cream will end up forming a more firm ganache. A ganache with much more cream than chocolate will form in a more fluid softer ganache.
Too much overall fat within this type of ganache will lead to a split ganache. The fat droplets will coalescence and make the liquid ganache appear greasy, and the solid ganache to feel grainy in texture.
Cream: The cream contains the bulk of the water, and is classified as the water phase in this case, even though it has small amounts of proteins and fats floating within it.
It is this water phase which absorbs or dissolves many of the non-fat components from the chocolate.
Again, if there is not enough water in the ganache, there isn’t enough of a water-phase for the fats to be evenly distributed. Just imagine trying to back people into a tiny room versus a very large room. In the tiny room it is harder for the people not to touch. We don’t want the fat globules to meet and coalesce. We want them to stay apart from one another within the aqueous phase.
Sugar: The melted chocolate is mixed with the heated cream, and the sugar crystals locked within the fat of the chocolate are released and dissolve in the water-phase.
If more sugar is added to the ganache aside from the sugar already contained in the chocolate, than it too will be dissolved in the water phase. However, higher sugar concentrations also makes the aqueous phase more viscous (thicker) due to high levels of dissolved sugar.
Cocoa solids : This is the non-fat component of the cocoa bean or seed (the other bean the cocoa butter), and is mostly made up of fibre or carbohydrate molecules from the kernel of the seed. As the melted chocolate and cream mix together, these non-fat cocoa solids enter the water phase and absorb the water.
The little cocoa solids therefore can expand in size as they absorb the water, making less water available within the ganache. In my opinion, this may be one reason why dark chocolate ganaches can split more easily than milk or white ganaches, especially if there isn’t enough cream or water. Since they have a higher concentration of these cocoa solids, they absorb more water and therefore limit the aqueous phase for which the fat can be distributed in, causing them to coalesce and the emulsion to break.
This expansion of the cocoa solids in the aqueous phase can also be useful at keeping the fat droplets away from each other as they crystalize. In an emulsified emulsion, they may act as “stability insurance” by decreasing the ability for the fat droplets to merge, ensuring the fat droplets don’t move and coalesce into one another.
These are already floating around in the cream, and continue to float around in the water phase of the ganache.
The Crystallization Of A Ganache
You can see the progression of the ganache from (a) to (c) to (d). The orange fat globules in (a) begin to grow fat bridges as they crystalize (c), until these bridges connect the fat globules and form a network (d). Once the fat crystalizes, the ganache ceases to be an emulsion and becomes a bio continuous system. You can see in image (d) that the non-fat cocoa particles disperse between the fat globules and swell, limiting the ability of the fat droplets to coalesce.
The research paper goes into more details about other experiments conducted, but for the purpose of this summary we will leave it at this. Below I will include a few practical helpful tips for working with ganache in the kitchen.
Troubleshooting in the kitchen
The following are some quick tips from my own chocolatier experience, and is not from information found in the preceding research paper.
If your ganache is split, or not coming together, it could be one of a few reasons that I’ll go over below. A split ganache appears greasy, grainy, and streaky. An emulsified ganache will be smooth and homogenous.
Just as a reminder, here is a very brief description of how to create a simple ganache. Scale your chopped chocolate into a bowl (the smaller the pieces, the easier it will melt). Heat up your cream (or juice or puree) and remove it from the heat just before it boils (you will see it begin to sizzle on the edges). Pour it over the chocolate and mix. Add your butter and/or alcohol at this point. The key is to ensure the chocolate and butter is melted while the ganache is still in the 35-40°C range. Then you can mix it until it is emulsified. Using a hand blender will ensure a good emulsification and smoother ganache.
A ganache, especially a dark chocolate ganache, should be below 45 or 40°C before you try to emulsify it together. If the ganache is too hot, whisking or using a hand blender likely will not work. Allow it to cool, optimally between 35°C-40°C, then attempt to bring it together.
However, a dark ganache shouldn’t be worked (emulsified, whisked, or ingredients added) below 34°C. Mixing it at too low a temperature may also break the emulsification. You want to ensure all your fats are in liquid form before being emulsified so that they can be as small as possible as they are broken up into droplets.
Amount of Water (cream)
If it is still not coming together and quite viscous or thick, try heating up some cream (or whatever liquid you are using) and add it little by little into the ganache as you mix it. It’s hard to say how much cream, as this would depend on the the size of your ganache. As you add this warm cream, mix the ganache and you should see it come together. If not, try adding a bit more cream.
Tools & Agitation
You don’t want to agitate your ganache too much. Especially if it is intended to be a very firm ganache, which means there is less cream or water overall. Mix it until it is combined and emulsified, but don’t overmix it, as it could break the emulsion.
Whisks add too much air. An electric hand blender works really well emulsifying the ganache. Just make sure that you don’t incorporate too much air into the ganache. Air pockets contain little amounts of oxygen from which bacteria can grow. It also alters the structure of the ganache.
I have noticed that dark chocolate ganaches with a large amount of fruit puree tend to be more susceptible to splitting, especially if they are too hot, too cold, or borderline do not contain enough liquid. I don’t have this problem with milk or white chocolate ganaches, likely due to less cocoa solids, so that the fruit fibers and cocoa solids don’t have to fight over the water available. This is just my hypothesis.
This work by Saglio et al. is wonderful, as it helps us visually and theoretically understand what is happening to our ganaches. Although we are told what to do and what not to do, understanding why can sometimes push us to really stick to some of the rules necessary for a successful ganache.