Thursday, February 23, 2023

The Deliciousness of Chocolate: A Scientific Study

Environmental & Science Education, STEM, Health, Nature of Science, History of Science, Sustainability, Global Change, Climate Change, Models, Culture

Ed Hessler

One way to make a chocolate bar last a long time is to research its structure and properties. Three researchers at the University of Leeds, UK did just that. Their research is found in a recently published jawbreaker of a paper - title and content, in the ACS publication, Applied Materials and Interfaces journal. The research has applications such as more satisfying chocolate eats that are healthier and a greener planet.

The research is about the "mouth-feel" of chocolate, using materials such as real chocolate candy and artificially made materials such as a "tongue" and saliva in order to control variables.

I've chosen a few items to highlight from the technical paper which is fully accessible as well as a media report.
--The author list includes information about the researchers and affiliations.

--The chocolates - all dark and all off the store shelf. 

--Figure 1 shows a schematic of their tribological performance. (Tribology is the study of wear, friction, and lubrication.). Three stages of mouth-chocolate interactions were measured   (A) licking stage: initial perception of the chocolate by tongue where chocolate is a countersurface, (B) molten chocolate/initial mastication: chocolate has undergone a phase transition to molten state, and (C) bolus before swallowing: chocolates mixed with the saliva.

--Figure 7 shows what the licking stage, molten state and boli look like and other detailed information.

--The conclusions, one of which notes that this is "the first systematic investigation of an edible PCM - phase change materials - containing solid particles (i.e., chocolate) far...the closest approximations to the real tongue-palate contact. (T)he fat content of dark chocolates appeared to be the most influential  factor on the lubrication behavior (in the mouth). ...Altogether, we hope that the knowledge is ... attractive (enough) to facilitate engineering of PCM and other metamaterials (I found this link useful.) that are often subjected to tribological stresses."

The Star Tribune published an article from the Washington Post by Maria Luisa Paul of the about the study. "Why chocolate is so very delicious, scientifically speaking" February 19, 2023. It requires a subscription to access. Here are a few things she reported.

--Fat content matters a lot.
--When chocolate first comes into contact with the tongue - the  'licking phase'" -" a phase many of us know well as the time "when the smooth 'chocolate sensation' is set into motion. During the melting phase "and saliva enters the mix, solid cocoa particles in the chocolate are released, along with a rush of happiness-boosting endorphins." The "silky sensation is  a product of its fat droplets making cocoa's otherwise gritty particles go down smoothly in the mouth."
--Does this mean that for enjoyment chocolate has to be high in fat? In an interview with one of the authors Paul was told "if the chocolate is coated in fat, it doesn't necessarily matter whether the chocolate itself contains much fat.," i.e., not too much fat is needed after the initial coating. This made me think of the  real estate trade; the value of a house depends on location, location, location. This is also true for the location of the fat in chocolate candies.
--Research team member Anwesha Sarkar noted that "the biggest bottleneck in designing food is the test and texture. If we understand the mechanics of why something is delicious it is easier to re-create more healthy and sustainable versions".

While I said this near the beginning, this paper also shows the importance of controlling as many variables as possible in designing research including a metamaterial -- the artificial tongue -- to yield the most credible evidence possible.

And to round out the taste of chocolate, the trailer for the film Chocalat (all 1 m 58 s of it) which I've not seen. And Joanne Harris's book about Vianne Rocher who runs head on into a stiff, no-nonsense parish priest in a small French town for whom Easter and chocolate should not co-exist. The book, which I have read, provides a glimpse into a chocolatier's life. Furthermore, it tastes of chocolate candies some of which I'd never heard of but would like very much to chew.

Finally, Paul's reporting closes with a perfect sentence. "That's the magic of chocolate--according to science." Science, especially as tools become available, e.g., 3-D printing can reveal that magic without destroying it, making it even more magical.

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