Tempered chocolate

History

As far back as the mid-1800s, chocolate makers knew crystallization mattered, with manuals stating that top-quality chocolate needed a glossy, smooth surface, a crisp snap, and a pleasing feel in the mouth. In 1902, makers believed that fast cooling made chocolate look and feel better. By 1931, a process called tempering was invented to stop bloom, though no one understood how it worked until the 1970s. Jean Tobler is credited with creating tempered chocolate.

Outline

Tempering chocolate aims to produce the most stable cocoa butter crystals. The process involves crystallizing a tiny fraction of the fat, about one to three percent, into a specific structure. These crystals act as seeds, guiding the remaining fat to solidify correctly. The method has four stages: first, heat the chocolate to 40 degrees Celsius to fully liquefy it.

Next, cool it to 32 degrees to start crystallization. Then, hold it at 27 degrees to encourage crystal growth. Finally, warm it to between 29 and 31 degrees, which melts any unstable crystals. Applying high shear breaks existing crystals into smaller pieces, creating more nucleation points.

This shear also generates heat, melting unstable crystals so they can reform into the desired Form V. Too much shear, however, can melt all crystals. Over-tempering makes chocolate harder, stickier, and less glossy. Once tempered, the chocolate can be poured into molds or used in an enrober, where cooling allows the fat to crystallize onto the nuclei. Poor tempering leads to a gritty texture or a white bloom on the surface.

Effect of additives

Tempering milk chocolate is more challenging than dark chocolate because milk fat lowers the seeding temperature to 84.9 F, compared to 94.1 F for dark chocolate. In some countries, fats substituted for cocoa butter alter texture and properties by forming a eutectic system. Sugar lowers the melting point of crystal structures, theorized to act as crystallization nuclei. Lecithin slows fat crystallization, as researchers theorize it coats sugar molecules, creating a surface that fat crystallizes onto with difficulty.

Industry

The conditions for tempering are difficult to control in large-scale productions. Chocolate stored at around 45 C is cooled in tempering machines, where stirring ensures all chocolate touches the cool sides. Faster shearing increases the rate of crystallization. In tempering machines, chocolate passes through three or four temperature zones: the first cools to where crystals can form, the second reduces temperature further and shears at a higher rate to create different crystal types, and the third raises the temperature so correctly formed heat-resistant crystals remain.

Some machines include a final stage where nuclei stabilize through continued shearing and slow heating, called maturing the temper. In small-scale production, tempering is done by hand on a marble table with areas at different temperatures. Chocolate is poured on a cooler area and mixed with a scraper to form crystals, then moved to a warmer area to melt unstable crystals. Skilled makers assess temper by putting chocolate on their lip, feeling a cooling sensation when tempered.

Others use a temper meter that observes whether chocolate sets quickly when cooled. More sophisticated devices use electric cooling to standardize cooling rate and analyze results with computers. Crystal forms can be measured using a differential scanning calorimeter.