Tempering is a technique applied in chocolate production to create chocolate that is glossy, has a good snap and is more resistant to chocolate bloom. It involves cooling liquid chocolate while agitating it until a small amount of cocoa butter crystallizes. The liquid is then heated to only maintain the most stable crystal forms, which serve as nuclei for the rest of the cocoa butter to solidify around.
History
editIn 1902, chocolate makers believed the texture and appearance were improved when chocolate was cooled rapidly. By 1931, the tempering process was developed to control chocolate bloom, but it was not understood how it worked. The effects on the crystal structure were only understood by the 1970s. By the 1950s, the tempering process involved cooling chocolate to 86 °F (30 °C), until it was "mushy", then raised to 91.4 °F (33.0 °C) before it was molded.[1]
The invention of tempered chocolate has been attributed to Jean Tobler.[2]
Background
editBy definition, most of the fat in chocolate is cocoa butter. Like all fats, cocoa butter is made up of several triglycerides, which solidify at different temperatures and rates.[3][4] When these crystallize, there are six different structures they can form (traditionally named by the chocolate industry I through VI), and only one of these (V) produces a snap and gloss desired by consumers.[3][5][a] The ability to crystallize in different forms is known as polymorphism. Of these forms, ones that are denser and have lower energy structures are harder to melt.[8] Chocolate will naturally crystallize into Form V when it is cooled to 93.2 °F (34.0 °C) and then mixed for several days. Tempering is a process to speed this up.[9]
Outline
editThe purpose of tempering is to create the most stable form of cocoa butter.[10] In tempering, a small amount of fat is crystallized (1–3%), creating nuclei which help the rest of the fat crystallize in the correct form.[11][12]
Tempering has four steps:[13]
- Heat to 122 °F (50 °C) to melt the liquid completely
- Cool to 89.6 °F (32.0 °C) to begin crystallization
- Crystallize at 80.6 °F (27.0 °C)
- Heat to convert any unstable crystals 84.2–87.8 °F (29.0–31.0 °C)
High shear breaks down crystals, and distributes them throughout the building, creating more nuclei for fat to crystallize onto. It also creates heat, which allows unstable crystals to melt and take on Form V. If there is too much heat, all the crystals will melt.[9] Over-tempering increases hardness and stickiness, reducing gloss and lightness.[14] After the chocolate is tempered, it can be used, for example by deposited in molds or being used in an enrober. In these uses, it is cooled, allowing the liquid to crystallize on the nuclei.[15][16]
A chocolate bloom, a white powdery substance appearing on the chocolate's surface can form if tempered incorrectly, as well as for other reasons.[4]
Effect of additives
editIt is more difficult to temper milk chocolate, as the milk fat alters how the chocolate sets and its final texture. This lowers the temperature needed for the crystal seed to 84.92 °F (29.40 °C), compared to 94.1 °F (34.5 °C) for plain chocolate.[17] It is also made more difficult in some countries where different fats can be substituted, as these fats similarly alter the texture and properties as a eutectic system is formed.[4]
Sugar lowers the melting point of crystal structures, as they are theorized to act as nuclei. The addition of lecithin somewhat slowed the rate at which the reaction began, as researchers theorize it covers the sugar molecules.[18]
Industry
editConditions needed for tempering are difficult to control in large-scale productions.[12]
Chocolate, stored at around 113 °F (45 °C), must be cooled for the fat to crystallize.[19] They are cooled in tempering machines, where chocolate is stirred so it all touches the cool sides.[19] As it is stirred, the material is sheared. The faster it is sheared, the faster the rate of crystallization. As it is sheared in tempering machines, chocolate is worked upwards, through about three or four different temperature zones. In the first zone, the temperature is cooled to the point where crystals can form. In the second, the temperature is reduced further to create different types of crystals, and it is sheared at a higher rate. In the third and final, the temperature is raised, as any correctly formed crystals, which are heat resistant, will not melt in this stage. Some machines include a final stage, where the nuclei are allowed to stabilise by continuing to shear and slowly heat the chocolate. This is known as maturing the temper.[20]
In small-scale production, tempering is done by hand. This is done on a marble table, where chocolate can be moved across different areas and heated to different temperatures. Initially poured on a cooler part, it is mixed using a scraper causing crystals to form. It is then moved to a warmer part of the table, where unusable crystals melt. Skilled chocolate makers assess if chocolate has tempered by putting some chocolate on their lip; it is tempered when they can feel a cooling sensation. Other chocolate makers use a machine known as a "temper meter". This machine observes whether chocolate sets very quickly when cooled, which indicates it has been successfully tempered. It is desirable for enrobing and molding to have the chocolate begin to set at a higher temperature.[21] More sophisticated devices use electric cooling to standardize the rate of cooling and analyse results using computers. The form of crystals present can be measured using a differential scanning calorimeter.[22]
Domestic
editIn a home setting, small amounts of set chocolate are grated into liquid chocolate that has been cooled to 86 °F (30 °C). This is only applicable to chocolate containing cocoa butter and the seeding chocolate needs to be distributed throughout the liquid.[9]
See also
editNotes
editReferences
edit- ^ Snyder, Olsen & Brindle (2009), p. 620.
- ^ Poelmans & Swinnen (2016), p. 20.
- ^ a b Beckett (2019), p. 81.
- ^ a b c Beckett (2019), p. 82.
- ^ Beckett (2019), p. 84.
- ^ Beckett (2019), p. 85.
- ^ Louisel et al. 1998, p. 426
- ^ Beckett (2019), p. 83.
- ^ a b c Beckett (2019), p. 86.
- ^ Afoakwa et al. 2008, p. 128
- ^ Beckett (2019), p. 95.
- ^ a b Hendrik et al. 2023, p. 1556
- ^ Afoakwa (2016), p. 128.
- ^ Afoakwa (2016), p. 317.
- ^ Afoakwa (2016), p. 298.
- ^ Pirouzian et al. 2020, p. 1
- ^ Afoakwa (2016), p. 129.
- ^ Pirouzian et al. 2020, p. 2
- ^ a b Beckett (2019), p. 95–96.
- ^ Beckett (2019), p. 97.
- ^ Beckett (2019), pp. 97–99.
- ^ Beckett (2019), p. 146.
Sources
edit- Afoakwa, Emmanuel Ohene (April 8, 2016). Chocolate Science and Technology. Wiley (publisher). ISBN 9781118913789.
- Afoakwa, Emmanuel Ohene; Paterson, Alistair; Fowler, Mark; Vieira, Joselio (2008). "Effects of tempering and fat crystallisation behaviour on microstructure, mechanical properties and appearance in dark chocolate systems". Journal of Food Engineering. 89. doi:10.1016/j.jfoodeng.2008.04.021.
- Beckett, Stephen T (2019). The Science of Chocolate (3rd ed.). Croydon, United Kingdom: Royal Society of Chemistry. ISBN 9781788012355.
- Hendrik, Nathaniel J; Marchesini, Flávio H; Van de Walle, Davy; Dewettinck, Koen (August 3, 2023). "Chocolate Tempering in a Rheometer: Monitoring Rheological Properties During and After Crystallization of Cocoa Butter". Food Analytical Methods. 16. doi:10.1007/s12161-023-02522-4.
- Loisel, C; Keller, G; Lecq, G; Bourgaux, C; Ollivon, M (1998). "Phase Transitions and Polymorphism of Cocoa Butter". Journal of the American Oil Chemists' Society. 75 (4). doi:10.1007/s11746-998-0245-y.
- Pirouzian, Haniyeh Rasouli; Konar, Nevzat; Palabiyik, Ibrahim; Oba, Sirin; Toker, Omer Said (2020). "Pre-crystallization process in chocolate: Mechanism, importance and novel aspects". Food Chemistry. 321. doi:10.1016/j.foodchem.2020.126718.
- Poelmans, Eline; Swinnen, Johan (2016). "A Brief Economic History of Chocolate". In Squicciarini, Mara P; Swinnen, Johan (eds.). The Economics of Chocolate. Oxford University Press. ISBN 9780191793264.
- Snyder, Rodney; Olsen, Bradley Foliart; Brindle, Laura Pallas (2009). "From Stone Metates to Steel Mills". In Grivetti, Louis Evan; Shapiro, Howard-Yana (eds.). Chocolate: History, Culture, and Heritage. Hoboken, New Jersey: Wiley. ISBN 9780470121658.