Where lumpy cocoa goes to die


Cocoa beans and leaves

You may not care all that much, but at a place like Nestle, lumps in powdered beverages such as cocoa, coffee and infant formula are a big, big deal. So much so that the company conducts quite a bit of sophisticated research into ways to eliminate said lumps in said cocoa, coffee and infant formula.

Recently, the company claimed a breakthrough -- a theory that predicts more accurately than ever before the way certain substances, such as sugar and other carbohydrates, will dissolve in water. It turns out that until a doctoral student turned two video cameras on a droplet of water as it dissolved a very thin layer of maltodextrose, this was a relatively poorly understood process.

The student, Julien Dupas of the École Supérieure de Physique et de Chimie Industrielles in France, spread the layers of carbohydrate so thinly that they refracted light as the water droplet touched them. Then he used that information and the "contact angle" of the water droplet and the carb layer to figure out how the solution process worked at its leading edge.

I was intrigued that so much work went into what, for me, was a matter of pouring water into a cup containing powder and stirring, so I read Dupas's paper, published May 6 in a physics journal (here's the abstract). Suffice it to say that I didn't understand much, if any, of the complicated description and formulas therein, so I interviewed Laurent Forny,  a food scientist in the Nestle Research Center in Lausanne, Switzerland, who worked with Dupas on the research.

Again, I was pretty much overwhelmed, but I managed to take this away from our conversation: "What we [were] not able to predict before is what is the mechanism that drives the wetting," Forny said. "We didn’t know why the droplet was spreading and why in some cases [wetting] better, in some cases [wetting] worse."

Or, as Nestle said in a news release, the research shows "for the first time that the way a drop of water spreads over certain soluble substances depends on the amount of water absorbed by the substance, as well as the softness of the part of the substance closest to the water." I would have guessed that someone had figured that out by now, but maybe not.

Anyway, if you have occasion down the road to lift a particularly smooth cup of hot cocoa to your lips on some cold winter day, you might think of Dupas and Forny and those video cameras and smile, knowing that such small pleasures don't come about by accident.

Lenny Bernstein writes the To Your Health blog. He started as an editor on the Post’s National Desk in 2000 and has worked in Metro and Sports.
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Lenny Bernstein · June 20