How Making Chocolate Is Like Mixing Concrete

How Making Chocolate(ˈCHäk(ə)lət) Is Like Mixing(miks) Concrete(ˈkänˌkrēt, ˌkänˈkrēt)

Researchers delved(delv) into the physics(ˈfiziks) of conching(käNGk, känCH), the stirring(ˈstəriNG) process that transforms ground cacao(kəˈkou,kəˈkāō) into a meltingly(melt) smooth(smo͞oT͟H) treat(trēt).

By Veronique(ˌverəˈnēk, ˌvārô-) Greenwood(ˈgrēnˌwo͝od)

What do chocolate and concrete have in common? More than you might think.

Chocolate is made by mixing liquid(ˈlikwid) and finely(ˈfīnlē) ground cacao beans in a device(dəˈvīs) that bears(be(ə)r) more than a passing resemblance(rəˈzembləns) to a cement(səˈment) mixer(ˈmiksər). In both cases, stirring(ˈstəriNG) tiny(ˈtīnē) granules(ˈgranyo͞ol) in a fluid(ˈflo͞oid) results in a substance(ˈsəbstəns) with very specific(spəˈsifik) properties — for chocolate, it’s a meltingly smooth mouthfeel, and for concrete, it’s a cohesive(kōˈhēsiv, kōˈhēziv), consistent texture(ˈteksCHər).

However, while physicists(ˈfizəsəst) have studied the physics of mixing concrete, fewer have taken a close look at the forces at work in chocolate conching, as the process is called. Now a team of physicists, funded in part by Mars, the confectionary(kənˈfekSHəˌnerē) company, published a paper last week in the Proceedings of the National Academy(əˈkadəmē) of Sciences(ˈsīəns) showing just what happens as the ingredients(iNG-,inˈgrēdēənt) of chocolate are given a stir(stər) on their way to becoming a delicious(dəˈliSHəs) treat.

When conching was invented(inˈvent) in 1879 by Rodolphe(rōˌdäf) Lindt, it could take more than a day of steady(ˈstedē) mixing for gritty(ˈɡridē) chocolate to grow smooth. Today, it is a shorter process. For this study, the researchers spun(spən) cacao powder(ˈpoudər) and a bit(bit) of oil in a conching machine for 40 minutes. They took photographs as the stuff went around, then added a different oil that reduces friction(ˈfrikSHən) during the final phase(fāz), which lasted an additional 20 minutes.

What they saw was that much like what happens in a cement(səˈment) mixer, the dry paste(pāst) formed from the powder and the fluid(ˈflo͞oid) made shaggy(ˈSHagē) clumps(kləmp). Then, at a certain point, it morphed(môrf) into a more liquid-like state(stāt) and started to flow(flō). Adding the oil near the end just encouraged the process, resulting in a shining(ˈSHīniNG) creamy(ˈkrēmē) liquid straight(strāt) out of Willy Wonka’s chocolate waterfall(ˈwôdərˌfôl, ˈwädərˌfôl).

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https://www.nytimes.com/2019/05/21/science/chocolate-conching-physics.html