What is tempering?

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The term tempering has two different meanings in the kitchen that tend to be ingredient specific.  One can temper eggs and one can temper chocolate.

Tempering Eggs:

The thickening properties of eggs are used in a variety of sauces and custards (flan, crème brulee, pot au crème, chawamushi, etc).  As the proteins in eggs cook, they thicken what they’ve been mixed in to.  However, if eggs are introduced directly into a liquid that is too hot, they will turn into scrambled eggs…not what you want in your carbonara!  The trick is to introduce some of the hot liquid to the eggs slowly while rapidly whisking, this brings the eggs to the correct temperature in an even, controlled manner, keeping them from seizing up.  Once the eggs have reached the same temperature as the rest of the liquid, the two can be mixed together normally.

Tempering Chocolate:

Tempering chocolate is far more complicated.  When discussing chocolate, tempering is the art of creating a specific matrix of cocoa butter crystals within melted chocolate via one of a couple of methods.  Properly tempered chocolate will set faster, have a better (more shiny) appearance, and a delightful snap when bit into.  Tempering is essentially a prerequisite for enrobing chocolate truffles and other candies (giving them a thin chocolate shell). 

Improperly tempered chocolate will set very slowly, be too brittle, and may display unattractive sugar crystals or cocoa butter sheen (known as “sugar bloom” & “fat bloom” respectively).

Tempering involves melting the chocolate, cooling it in a controlled fashion while stirring, then re-warming to a temperature below where the new crystals start to break down.  Though chocolate tempering machines exist, they are rather expensive, so most home cooks temper by hand, which generally requires practice and careful temperature monitoring for reliable results.

The methods most often used for tempering chocolate are:

1) Tabling –  Melted chocolate back and forth across a marble slab with a pair of paddles, cooling the chocolate at a controlled rate while encouraging crystal growth.  This method is the most difficult and really an art, but many artisan chocolatiers swear by the quality of temper it provides.

2) Seeding (aka Block Method) –  Chocolate is melted past the point when its internal crystals dissolve, then pieces of unmelted chocolate are stirred in to cool it down while providing seed crystals.  Seed-tempered chocolate does not need to be rewarmed unless it gets too cool (and consequently too thick for dipping/coating/mold use).

3) Cooling – Melted chocolate is stirred over an ice water bath until it starts to set, then re-warmed until it is melted but the crystals have not dissolved.

4) Direct Warming – Since chocolate is sold pre-tempered, if it is melted but kept below the temperature where its already existing crystals melt, it may be able to be used without using an active tempering method.  However, as soon as the crystal matrix melts it must be re-tempered using one of the above methods.

Important note: tempering chocolate by hand requires top quality, high cocoa butter chocolate to work well.  This grade is referred to as couvertures chocolate and contains a minimum percentage of 32% cocoa butter.  Cheaper chocolates have frequently had much of their cocoa butter replaced with cheaper emulsifiers like soy lecithin.

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