Shirley O. Corriher
American Chemical Society
New York, October, 2007
Chocolate (Theobroma "food of the gods")
Chocolate is a mixture of finely ground cocoa and sugar particles in a rich fat, cocoa butter. This fat, cocoa butter, has a sharp melting point, which just happens to be right at body temperature. You bite into hard, firm pieces of chocolate, seconds later, your whole mouth is filled with a luscious, thick liquid, sensuous aromas, and the sublime taste of real chocolate. This is a sensual experience far beyond taste alone.
Care of Chocolate
Chocolate does require tender loving care. It can suffer from storage conditions. Too moist or too warm and a grey coating will appear on chocolate. This coating is called bloom and there are actually two kinds of bloom. As you may suspect, one is caused by moisture and the other by warmth.
Sugar Bloom
If chocolate is not tightly wrapped, moisture from the atmosphere condenses on the surface when the temperature drops. This moisture dissolves some sugar from the chocolate. When the air warms again, the moisture evaporates leaving behind a gray film of very fine sugar called "sugar bloom."
Fat Bloom
If chocolate is held for six months or more at a temperature in the high 70s Fahrenheit, mid 20s Celsius, tiny amounts of some fats in the cocoa butter melt and float to the surface of the chocolate forming a gray film, "fat bloom." In appearance, fat bloom and sugar bloom look alike, but there is a slightly oily feel to the fat bloom.
Working With Chocolate
Working with chocolate can be startling! When you are melting chocolate, you can have glistening, thick, oozing chocolate, and then suddenly, just a few degrees hotter, you have dark, grainy lumps in pale, golden oil.
Equally startling, your shiny, flowing, melted chocolate can suddenly become a dull, solid, grainy mass. Overheating and moisture cause these two most common problems with chocolate.
Overheating
Chocolate melts at a relatively low temperature--it literally melts in your mouth. When you heat chocolate, the cocoa butter crystals melt and the chocolate becomes fluid, but if you get the chocolate too hot, it can separate into burned, blackened cocoa particles and pale golden liquid.
We both scoured every source we could imagine. It seemed like such a simple question, “At what temperature does chocolate separate into cocoa particle and melted cocoa butter?” I finally got Dr. Paul Dimick, chocolate expert at Penn State University. He explained that cocoa butter, like most natural products, is a complex mixture of fats. It contains small amounts of fats that do not melt until high temperatures--over 200°F/93 °C.
When French pastry expert Bruce Healy asked me, “How hot is too hot?” I thought that this was an easy question--somewhere around 120°F. It seems that a lot of things say, “Don’t heat over 120°F.” But Bruce pointed out that in Valhrona tempering directions they advise heating above 131°F. I though we could just look it up in Minifie, Confectionery, the technical chocolate bible. Bruce had already looked. It wasn’t there.
Cocoa beans from different locations are very different since the plants adapt to the climate of their surroundings. In a room at moderate temperature, say at 70°F/21°C, cocoa butter from Malaysian beans which grew near the equator would be quite firm, while cocoa butter from Brazilian beans which grow in a much colder mountain climate would be quite soft.
Dr. Dimick says that one of the major factors causing separation when heating is inadequate stirring. With constant stirring, you can exceed chocolate’s normal separation temperature by a little without ill effects. This separation temperature for dark chocolate is over 130°F/54°C (the exact temperature depends on the cocoa bean from which the chocolate was made), and for lighter chocolates it is 115°F/46°C, which is not very hot.
Chocolate can be safely melted in many different ways--on very low heat or over hot, not simmering water (avoid steam) or in the microwave at 50% power for semisweet, 30% for milk or white chocolate, stirring every 15 seconds. Heat and stir until the chocolate is just melted.
Moisture--Seizing
Chocolate's "seizing" (becoming a solid, grainy mass) is a sudden, totally unreal happening. It is as if a witch put an evil spell over your beautiful velvety brown liquid. Actually, this “evil spell” is caused by moisture. The tiniest bit of moisture, even steam, can cause flowing, shiny melted chocolate to become a solid, dull, grainy mass.
Dr. Richard Schwartz at Wilbur Chocolates explains this using a sugar bowl as an example. If you pour a cup of boiling water into a sugar bowl, it dissolves all the sugar--no lumps. But, if you dip the spoon that you just used to stir your coffee into the sugar bowl, you get little grainy lumps of sugar. The small amount of moisture from your spoon caused the dry sugar particles to glue together. This is exactly what happens when you get a little moisture on chocolate. The fine, dry sugar and cocoa particles glue together to change melted chocolate into a solid, grainy mass.
What can you do when chocolate seizes? Is there anything that you can do to retrieve it? Yes and no. Applying the sugar bowl example, if you add more water so that all the particles get wet, they will no longer stick together. Work a tablespoon of warm water into the grainy mess by breaking up the solid and pressing the mess with the back of the spoon. When this is incorporated, work another tablespoon in until you have a smooth shiny chocolate again. This slightly watered down chocolate is fine for many uses--icing, fillings, etc. but will not work for enrobing where you need a hard finished product.
Preventing Seizing
The Recipe--Enough Water-Type Liquid
Cooks have to check their recipes and make sure that there is enough water-type liquid in the recipe to prevent seizing.
In recipes containing water-liquid (this can be the water in butter, milk, heavy cream, eggs, etc.) and chocolate, there is going to be a certain amount of water-type liquid that the recipe must contain to prevent seizing. (An amount that is enough to wet all the cocoa particles.) See Definitions Pages for chocolate liquor, high-percentage chocolates, etc.
With the regular 55% to 60% chocolates (bittersweet and semisweet that contain 55% to 60% chocolate liquor), the minimum amount of water-type liquid needed to prevent seizing is 1 tablespoon per 2 ounces of chocolate. High-percentage (60 to70%) chocolates, which contain more cocoa particles, require more liquid (1 1/2 tablespoons water-type liquid per 2 ounces of chocolate). Unsweetened chocolate requires 2 tablespoons of water-type liquid for 2 ounces of chocolate. Any recipe with less liquid may cause the chocolate to seize.
Since high-percentage chocolates require more liquid, recipes that worked beautifully with regular chocolate (containing 55 to 60% chocolate liquor) may not work with the high percentage chocolates (chocolate containing 60 to70% chocolate liquor), which have many more cocoa particles that have to be wet. So, you may well have a recipe that you have made for years with regular chocolate that is a disaster with high percentage chocolates.
Add Melted Chocolate to Other Ingredients
To prevent seizing, cooks must avoid any situation where you have a small amount of liquid with chocolate - for example, when combining melted chocolate and the other ingredients in the recipe. If you pour liquid into chocolate, you can have that dreaded situation of a lot of chocolate and a little water-type liquid. Cooks should add the melted chocolate to the other ingredients with stirring to insure that there is always plenty of water to wet all of the cocoa particles.
One of the few situations where you can get away with adding liquid to chocolate is in the food processor with the processor running when you add hot cream to finely chopped chocolate, but Alice Medrich cautions that the cream must be added in less than 15 seconds.
Ideally, to melt chocolate, chop it into small pieces or process it a few seconds in the food processor. These fine pieces melt faster and more evenly than large lumps. Stir the chocolate constantly while melting to keep the temperature even throughout.
Unfortunately, there are many truffle recipes that instruct adding a small amount of liqueur to melted chocolate. The recipe usually says something like the chocolate will thicken. Thicken nothing! It is seizing.
Watching the voluptuous, flowing, melted chocolate turn instantly into a grainy rock is a startling, terrifying experience. It is not something that you forget. The two lessons that I have learned from seizing are: Lesson one, never even think of combining melted chocolate with an ingredient unless there are enough water-type liquid ingredients to wet all the chocolate particles.
Lesson two, always add melted chocolate to other ingredients, not the other way around. If you add a liquid to melted chocolate, you risk having the terrible situation of a lot of chocolate with too little liquid. Even if this lasts for a just few seconds, tiny seized particles of chocolate can appear.
Ganache
Why I Worry About Ganache
The classic method to prepare ganache is to place coarsely chopped chocolate in a heatproof bowl, bring heavy cream to a boil, pour the hot cream over the chocolate, and stir together until it thickens. This is adding liquid to chocolate, which I just said can cause seizing. If the cream and chocolate are not successfully combined, the ganache can contain little hard, undissolved chocolate specks or it can separate with an oily, shiny glaze on top.
Using the classic technique, ganache can fail even in the hands of a master. In a tiny kitchen in Erice, Italy I watched as a French restaurant owner/chef poured the boiling cream over finely chopped chocolate while a famous French pastry chef stirred vigorously. The famous chef got a product that he was unhappy with two out of five times. He pointed out the tiniest chocolate specks in the otherwise smooth mixture. There were only the three of us there; the two chefs spoke little or no English, and I spoke no French. So, I could not ask my burning question, “Why not add the chocolate to the cream instead of the cream to the chocolate? That has always worked for me.” But, this was one of the most famous pastry chefs in France. I remained respectfully silent.
I strongly suggest heating the cream almost to a simmer in a medium skillet, then removing it from the heat. Allow it to cool about 1 minute, then dump the finely grated chocolate in all at once. Shake the skillet just enough to settle the chocolate, and then stir to combine.
Melting Chocolate with Liquid
If you have to deal with chocolate that has grey sugar bloom on the surface, it may well seize when you try to melt it, even if you avoid getting any steam near it. To prevent seizing, you should melt the chocolate with sufficient liquid. Melting the chocolate with other recipe ingredients (butter or liquids) is a fail-safe way to handle it. As long as you have the necessary amount of water-type liquid, you avoid all risk of seizing.
You will notice that experienced dessert cooks write their recipes in just this way--melting the chocolate with liquid from the recipe. Maida Heatter melts chocolate and butter together in her Palm Beach Brownies, Alice Medrich melts chocolate, butter and corn syrup together for her glassy smooth chocolate icing.
Cold Ingredients
A different problem is blending cool chocolate with ice cold ingredients. When you add cool melted chocolate to ice cold ingredients, the cold makes the fat in chocolate, the cocoa butter, harden instantly. For example, if cool melted chocolate is drizzled into ice-cold whipped cream, tiny flecks of solid chocolate may form instantly (a chocolate-chip mousse!) rather than an even blend of chocolate and cream.
To avoid a chocolate chip mousse, the chocolate that you are adding should be a little warm, right at body temperature. This will not be hot enough to deflate the whipped cream, but warm enough to blend smoothly.
Another solution to the problem is to blend the chocolate and the cream before the cream is whipped. You can melt the cream and chocolate together and then cool well, about 5 hours or overnight. The chocolate cream whips beautifully for a perfect chocolate mousse.
Chocolate At a Glance
What to Do |
Why |
Chop chocolate into small pieces before melting it. |
For quicker and more even melting as chocolate may burn before large lumps |
Melt chocolate over very low heat, warm not boiling water, or in the microwave. |
If chocolate is heated beyond 120°F/49° C it separates and burns. |
Stir chocolate as it melts. |
To keep the temperature even. |
Use at least 1 tablespoon of liquid for every 2 ounces of 55% chocolate. Use 1 1/2 tablespoons for each ounce of 60% to 70% chocolates and 2 tablespoons of liquid for unsweetened chocolate. |
The minimum of liquid necessary to prevent the dry particles from sticking together (seizing). |
Avoid getting even a drop of water or steam into melted chocolate. |
A small amount of water causes dry particles in chocolate to stick together and seize. |
When possible, melt chocolate with other liquid ingredients in a recipe. |
Adding adequate liquid at the beginning of melting prevents seizing. |
Add water to seized chocolate to bring it back to a liquid state. |
Sufficient liquid wets all the particles so they no longer stick together, but the chocolate is not suitable for all uses. |
Do not mix warm melted chocolate into ice cold ingredients. |
Cold ingredients cause the cocoa butter to harden immediately. |
© Copyright Shirley O. Corriher, 2007