Published on December 30th, 2014 | By: April Gocha, PhD0
Keep calm and shine on: Material science behind chocolate’s surface sheenPublished on December 30th, 2014 | By: April Gocha, PhD
When you think about it, there aren’t too many foods that we want to change states of matter while we’re eating them.
You’d probably be a bit dismayed if your steak vaporized to gas. And who hasn’t downed a certain alcoholic drink quickly enough to skip the in-mouth appearance of solids? (You haven’t? My advice is simple—chug.)
But chocolate is one delightful exception—we deeply appreciate chocolate’s transformation from solid to gooey liquid. We actually want it to melt in our mouths.
However, breathing steak vapor may not be as far-fetched as you might think.
Paris-based “culture lab” Le Laboratoire (which now has a location stateside in Cambridge, Mass.) is a pioneer of unusual and innovative thinking, crafting experience experiments like edible ice cream wrappers and the oPhone—which sends “aroma messages” instantaneously from one location to another.
“Many of the questions that we face today—questions of innovation, of change—are not really questions we can deal with in a classical science lab,” David Edwards, biomedical engineer and Le Laboratoire founder, says in a WUNC article. “And I think that’s why culture labs are showing up increasingly around the world. By opening the creative process up to the public, it leads to a better understanding of how the world’s changing, and why it’s actually thrilling that it is.”
Another of Le Laboratoire’s interesting innovations is Le Whif, which delivers a “cloud of flavor” from a large orb-like glass bowl. Whiff consumers dip their head into a cloudy bowl, inhaling a flavor such as chocolate. A variation of the experience is Le Whaf, which turns liquid—including alcohol—into inhalable gas. (And which is now commercialized into a portable, at-home Le Whaf device.)
According to Le Laboratoire’s website, “Scientists today are exploring the creation of fine respirable aerosols with an aim to deliver especially large quantities of drugs, like antibiotics, to the body through inhalation. The use of ultrasonic waves, created by piezoelectric crystals (a technology inherent in the workings of Le Whaf) is a method particularly explored by the new biotechnology startup, Pulmatrix.”
More than a fun experiment in how we think about and experience our senses, the concept was spun off into a company called AeroLife. AeroLife markets a product that’s “an air-based smart nutrition system that delivers powdered blends of vitamins, supplements, and flavors,” according to the website.
The handheld device—somewhere between a lipstick case and an e-cigarette—allows users to inhale a breath of flavored or supplemented air to experience a sensation, administer aerosolized vitamins, or maybe someday even deliver medications.
Gaseous experiences aside, chocolate is nonetheless likely to remain one of our favorite edible state transformations to experience.
Chocolate as we know it is a combination of cocoa solids and cocoa butter (which come from fermented and roasted cacao seeds) mixed with sugar and other fats. (Dark chocolate has a greater percentage of cocoa solids; milk chocolate also adds milk to the mix; and white chocolate is completely sans cocoa solids—and so not really chocolate—in case you were wondering.)
But chocolate is fascinating for more than its deliciousness—the stuff also has some pretty complex material science going on behind the scenes.
When chocolate solidifies, the fats within undergo polymorphous crystallization into six different forms, each with a different melting temperature and with different properties—in chocolatemaking, the formation of these crystals must be carefully controlled through a process called tempering because they affect the qualities of the resulting chocolate.
Crystals with higher melting temperatures are the reason why good chocolate is glossy and snaps apart rather than crumbling. Crystals of the highest melting temperature (97°F), called type VI crystals, actually take weeks to form within chocolate.
Cocoa butter crystals are really important to the quality of chocolate, and they’re also really important to its appearance as well. If stored in less-than-ideal conditions, like with too much humidity or fluctuating temperatures, chocolate can develop an unfortunate aesthetic called bloom, which appears as white-ish splotches on the chocolate’s surface.
If you’ve seen chocolate bloom before, you might have mistaken it for microbial growth. (Not to be confused with microbial growth in your gut—which does chocolate good!)
But have no fear—chocolate bloom is neither bacteria nor fungi, and it doesn’t mean that your chocolate is ruined. It’s perfectly edible and perfectly safe to do so.
Chocolate can develop either sugar bloom or fat bloom, which are caused by separation of crystals of sugar or fat, respectively, from the chocolate mixture. It’s kind of like the separation of oil and vinegar in a vinaigrette—it looks weird, but it doesn’t affect the taste of the dressing.
Chocolate bloom is unappealing on chocolate, however, so chocolatier’s and chocolate manufacturers alike want to know how to get bid the bloom bye-bye as much as possible.
Scientists at Fraunhofer have had their eyes (and probably taste buds, too) on chocolate and have found that in addition to improper storage, other conditions can cause chocolate’s unsightly blemishes. And they want to fix that.
“Production of Christmas baked goods already starts in July,” Wolfgang Danzl, food quality expert at Fraunhofer, says in a Fraunhofer press release. “This is where the problem lies. Fat bloom does not appear immediately after production, but instead appears days or even weeks later. It can be one of the consequences that come from storage that is too warm, or under temperatures that sharply fluctuate.”
Danzl and Fraunhofer colleagues studied the evolution of fat bloom that develops on chocolate-coated cookies, candies, and confections.
“It is not uncommon for residual chocolate at the end of the coating stage to flow right back to the start,” Danzl explains in the release. “During this recycling, the shortening used for filling and baking is washed off. We were able to prove that for the first time…The filling fats cause the chocolate to crystalize more slowly, making the coating softer. This allows the fat to accumulate even more efficiently. Fat migration is facilitated, which in turn can lead to fat bloom formation.”
The researchers found that chocolate with a high proportion of cocoa butter and less of the other fats is very likely to form fat bloom on its surface. And although nut oil and lauric fats, such as coconut oil, make the chocolate coating soft, they also don’t mix well with cocoa butter. The not-so-mixed mixture destroys crystalline structure of the fats, also leading to likely formation of fat bloom.
The release fails to allude to which fats and conditions prevent the formation of fat bloom. However, apparently Fraunhofer scientists are available to consult with chocolate coating producers to investigate and advise solutions for fat bloom development, per the release. (Sounds like there might be money-making consultant opportunities keeping them tight-lipped.)
As for you chocolate consumers, just remember this: That blotchy chocolate is still edible, so keep calm and chocolate on.
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