New method produces flavourful, antioxidant-rich chocolate

Researchers have found a way to make chocolate more flavourful and nutritious with greater levels of antioxidants.

Chocolate is known to have health benefits. It can potentially lower blood pressure and cholesterol and reduce stroke risk.

Cocoa undergoes several steps before it takes shape as a candy bar. Workers cut down pods from cocoa trees, then split open the pods to remove the white or purple cocoa beans.

They are fermented in banana-lined baskets for a few days and then set out to dry in the sun. Roasting, the next step, brings out the flavour.

But some of the healthful polyphenols (antioxidants) are lost during the roasting process, so the researchers wanted to figure out a way to retain as much of the polyphenols and good flavours as possible.

"We decided to add a pod-storage step before the beans were even fermented to see whether that would have an effect on the polyphenol content," said Emmanuel Ohene Afoakwa at the University of Ghana.

"This is not traditionally done, and this is what makes our research fundamentally different. It's also not known how roasting affects polyphenol content," Afoakwa said.
Afoakwa's team divided 300 pods into four groups that were either not stored at all or stored for three, seven or 10 days before processing.

This technique is called "pulp preconditioning." After each storage period passed, fermentation and drying were done as usual. He said that the seven-day storage resulted in the highest antioxidant activity after roasting.

To assess the effects of roasting, the researchers took samples from each of the storage groups and roasted them at the same temperature for different times.

The current process is to roast the beans for 10-20 minutes at 120-130 degrees Celsius.
Afoakwa's team adjusted this to 45 minutes at 116 degrees Celsius and discovered that this slower roasting at a lower temperature increased the antioxidant activity compared to beans roasted with the conventional method.

In addition, the beans that were stored and then roasted for 45 minutes had more polyphenols and higher antioxidant activity than beans whose pods were not stored prior to fermentation, said Afoakwa.

He said that pulp preconditioning likely allowed the sweet pulp surrounding the beans inside the pod to alter the biochemical and physical constituents of the beans before the fermentation.

"This aided the fermentation processes and enhanced antioxidant capacity of the beans, as well as the flavour," he said.

Afoakwa said that the new technique would be particularly useful for countries in Southeast Asia and Latin America where cocoa beans produce a chocolate with a less intense chocolate flavour and reduced antioxidant activity.

The research was presented at the 249th National Meeting & Exposition of the American Chemical Society (ACS) in Denver.