The science of chocolates (Part I): Tempering & Emulsions
How would feel if we told you, every inch of your favourite chocolate dessert is nothing but pure physics and chemistry? Or that the range of techniques involved, in one spoon of chocolate, if measured in ropes, could circle the world at least once! Well, we hope you feel really good because if you do, you are in for a treat!
by Rukmini Roy
1 year, 10 months ago
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Firstly, considering we all love chocolates and desserts with chocolates, it makes for a fantastic topic of discussion. Secondly, believe us or not, every square inch of your chocolate dessert is nothing but pure physics and chemistry, and the range of techniques involved, if measured in ropes, could circle the world at least once! Reason why we will do this lesson in 3 parts; The first part will cover the science behind Tempering and Emulsions, the 2nd Mousse and Molten chocolate cakes, and the 3rd and final- Velvet effect techniques and Thermal shock technique. Yes, Thermal Shock Technique in chocolates and you’ve heard it quite right. Julia Child fans would find this a little more un-homecook-ish but its true that to have that perfect bite of your favorite chocolate dessert, you’d need to deal with Harvard level Science!
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Chocolate is the fermented, dried, roasted and grounded form of cacao beans, which can be separated into cocoa butter, a smooth, solid fat used in both food and cosmetics, and cocoa powder. Cocoa butter and cocoa powder are combined in different proportions with other ingredients to produce chocolate. Pure chocolate must be tempered before used or it tends to melt whereas compound chocolate, which is low-quality chocolate contains other fats beside cocoa butter, so it often doesn't need tempering.
Watch Chef Ramon Morato explain what Chocolate really is!
Science & Cooking by Harvard University
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The snap that is famous worldwide amongst connoisseurs of chocolate; what the chef wants to see in your chocolate making skills and  is nothing but the magic of what is called Tempering. A process that encourages the cocoa butter in the chocolate to harden into a specific crystalline pattern that helps it to maintain the sheen and texture for a long time, tempering my friend, is no child’s play.

This 8 minute video will show what tempering is

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Beta crystals are the goal of tempering. Unlike a lot of ingredients we work with, Chocolate can achieve 6 different crystalline structures, of which only the V-form or the Beta Crystals are what we try to achieve while tempering chocolate. If you heat and cool chocolate without controlling the temperature the crystallization of cocoa butter will result in bad crystals and your chocolate will bloom (appear matte and covered with white patches). Worst part is it will also crumble or might be soft rather than snap. Tempering controls the crystals so that only consistently small Beta crystals are produced which is smooth with a homogeneous texture, without white blooms and of course with “Snap”.

Given below are the steps that are involved in tempering:

Melting the cocoa butter in the chocolate completely

Cooking literature advises us to not get the chocolate over 120° F for it might burn the cocoa solids or cause the chocolate to irreversibly separate into solid and fat. But technically melting curves of chocolate tells a different story- that most of the fats in cocoa butter aren't melted until 122° F, and some requires heating as high as 131° F. This is because cocoa beans from different geographical locations vary in their composition. If tempering professionally, one must consult the manufacturer of the chocolate for best results.

Rapid cooling to about 82° F for dark chocolate & 79° F for milk and white.

This gets the crystallization of the good beta crystals started. This process also allows some undesirable beta-primes to form.  

A slight warming

Once cooled rapidly on a marble slab, the chocolate is heated back to 86° F for dark (84° F for milk and white) for a few minutes. This is done to help the beta crystals to continue forming. A final warming to 89° to 91° F for dark and 87° to 89° F for milk and white chocolate is done to kill the remaining undesirable beta-prime crystals that were formed.

Verifying that the chocolate is tempered

If the chocolate is tempered, a thin smear onto a piece of parchment or waxed paper will peel off easy after 5 minutes. This chocolate will also be shiny, not blotchy, and if tasted will be smooth. We hate to break your heart unless you want to wade through lumpy chocolate. If after the tempering process your chocolate do not tempers, start the tempering process again.

Chocolatier and Chef Ramon Morato explains in Harvard University about why tempering chocolates is necessary, the temperature changes involved in crystallization of chocolate and how to achieve it. An interesting video that’ll make you respect chocolate!

Science & Cooking by Harvard University
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Chocolate emulsions are a different story altogether. To have a beautifully elastic ganache you’ll need to maintain the temperature of friction. To demonstrate this, you’d need a bowl of chocolate (melted) at about 40 degrees and a bowl of water. Now, this water component can be anything- whether a fruit infused water, whether juice, or cream- it’s upto the flavour of ganache or chocolate emulsion you are looking at.

The chocolate break down

When we pour some water over chocolate and start whisking at a slow pace, you’ll face a classic chocolate component break down- the solids and fats would separate and form one big fat mass of lump. This is because the water gets the temperature of the chocolate mixture below the melting point of cocoa butter making it lumpy.

The Chocolate ganache build up

Surprisingly when added more water and whisked vigorously, the same broken lump of chocolate will rise to be a beautiful, shiny ganache. At this point, note the temperature. If you have a shiny ganache, the temperature of your final product will always be higher than the melting point of your coco butter which is 34–38 °C (93–100 °F)

Cooling

Your work is not over with ganache. If you want to incorporate the chocolate as in bonbons or moulds, you need to decrease its temperature down to 28 degrees, so that it thickens.

A snippet from the same video by Chef and Chocolatier Ramon Morato

Science & Cooking by Harvard University
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Everyday, our life goes through chains of chemical activities. From pure chemistry to pure physics, from our morning tea to our evening hot chocolate- its all the doing of simple science. In fact I’ll go as far as- some of the best cooks in the world’s best friend are thermometers!

We would love science if only we read beyond our books; interpreted everyday activities the way they are- the way they happen. 

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1. Science made chocolate perfect
2. What is Chocolate?
3. What is Tempering of chocolates?
4. Case Study 1: The science behind perfectly Tempered Chocolate
5. Case Study 2: The Science Behind Emulsification of Chocolates
6. A fitting footer for the chocolaty science
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