Structure of chocolate unravelled by synchrotron radiation

Think about a piece of chocolate. Imagine it melting in your mouth. The sensation is delicious. Now think of the same image, but this time the chocolate is covered by a white film on its surface. This white film is produced when chocolate is poorly crystallised or when it is stored under the wrong conditions. We ’eat’ also with our eyes, so such bad-looking chocolate seems less nice to the palate. Here is where scientists come into the picture. Researchers from The Netherlands working at the ESRF try to avoid this white layer, called fat bloom, by studying the structure of chocolate. Their aim is to optimise the pleasure of eating it. They publish this week in the Journal of Physical Chemistry B the structure of a component of cocoa butter and also the crystal structure of the most common form of cocoa butter in chocolate, a result that is of great importance for chocolate production. The ESRF synchrotron light was essential for this research.

There is a lot of science in the process of making chocolate. Dark and bitter sweet chocolate contain from 31 to 38% of cocoa-butter, 16 to 32% of cocoa powder and 30 to 50% of sugar. Cocoa butter determines the physical properties of the chocolate. It has a high degree of crystallinity and may crystallise in six different crystalline forms in the course of the production process. This process includes tempering, which consists of repeatedly heating the chocolate to a specific temperature and then cooling it down. It aims to bring the cocoa butter in one of the most stable crystal forms. The different crystalline phases are numbered from phase I to the most stable phase VI. The lower-numbered phases are unstable and do not give a good product, but manufacturers nowadays manage to set the chocolate in phase V. Nevertheless, even this chocolate phase can suffer from phase transition during storage, resulting in fat bloom. This explains the importance of crystallising the chocolate properly.

A team of scientists from the University of Amsterdam, with help of the ESRF, has made a major step forward by identifying for the first time the crystal structure of one of the three main triglycerides that make up chocolate butter. The triglyceride, called SOS, is a cis-mono-unsaturated type and represents one quarter of the chocolate butter. This breakthrough helps in better understanding the melting behaviour of cocoa butter and better controlling the production process. According to Dr. René Peschar, first author of the paper, “This work is expected to be highly relevant to confectionery research and industry and the first step to a better understanding of the mechanism of the fat bloom phenomenon at the molecular level.”

The researchers used the synchrotron light to collect data from which they determined this structure using the X-ray powder diffraction technique. They also stored completely molten cocoa butter at room temperature (around 22°C) for several weeks to get the phase V. Then they studied it at the ESRF with the same technique and managed to construct a crystal structure model of this cocoa butter phase V. “It is impossible to get these results with laboratory data; you really need a synchrotron facility because of its superior data quality”, explains Dr. Peschar, from the University of Amsterdam.

The chocolate research based on data measured at the ESRF has also had impact on industry. The Dutch machine manufacturing company ’Machinefabriek P.M. Duyvis’ acquired a patent concerning an improved method of making chocolate that is based on the results of experiments carried out by the Dutch researchers at the ESRF over the last few years. The company built a prototype, tested and fine-tuned it together with the University of Amsterdam and a major European chocolate producer. The company is situated in the middle of the "Zaanstreek", a region hallmarked by a huge diversity of foodstuff manufacturers and processing more than 20% of the world’s cocoa bean crop.

Source: European Synchrotron Radiation Facility

Related stories:

Scientists work to stop chocolate going the way of George Clooney
What do George Clooney and old chocolate have in common? Both are still delicious but have greyed with age – and while this certainly hasn’t damaged the image of the former ER star, it does detract from the appeal of the beloved mocha ambrosia, despite being perfectly safe to eat.
Fighting 'fat bloom' can mean a prettier look for Valentine’s Day chocolates
Chemists in England and the Netherlands have discovered a substance that could keep those boxes of Valentine’s Day chocolates, and other goodies, looking fresher and tastier. Their finding, which prevents formation of unsightly white films on the outside of chocolate, is scheduled for the March 12 issue of the ACS’ Journal of Agricultural and Food Chemistry.
Chocolate lovers fight proposed FDA change
Chocolate lovers are fighting a proposed change to U.S. chocolate standards that would allow other fats to replace cocoa butter.
89 percent of children's food products provide poor nutritional quality
Nine out of ten regular food items aimed specifically at children have a poor nutritional content – because of high levels of sugar, fat or sodium - according to a detailed study of 367 products published in the July issue of the UK-based journal Obesity Reviews.
Mars teams up with IBM to map cocoa genome
US chocolate and sweets giant Mars is teaming up with IBM to study and map the cocoa genome in a move which could enhance the production of stronger plants, the companies said Thursday.
Study indicates grape seed extract may reduce cognitive decline associated with Alzheimer's disease
A compound found in grape seed extract reduces plaque formation and resulting cognitive impairment in an animal model of Alzheimer's disease, new research shows. The study appears in the June 18 issue of The Journal of Neuroscience.
Synthetic cocoa chemical slows growth of tumors in human cell lines
A synthetic chemical based on a compound found in cocoa beans slowed growth and accelerated destruction of human tumors in laboratory studies, and should be tested further for cancer chemoprevention or even treatment, say researchers at Georgetown University Medical Center.
Cocoa could be a healthy treat for diabetic patients
For people with diabetes, sipping a mug of steaming, flavorful cocoa may seem a guilty pleasure. But new research suggests that indulging a craving for cocoa can actually help blood vessels to function better and might soon be considered part of a healthy diet for the prevention of cardiovascular disease.

News discussion:

Physics news