Flavanols from Ivory Coast beans were found to increase by 30% after roasting, while Java beans decreased by half, despite being roasted under the same conditions.
The discovery was made by Kothe et al. and results were published in the journal Food Chemistry.
Method: Indonesian and Ivorian beans
The researchers compared the impact of roasting on three bean varieties: one from the Ivory Coast and two from Indonesia (Java 1 and 2).
The scientists used pilot plant scale equipment to roast 5 kg of cocoa beans from each origin at multiple temperatures and measured flavanol monomers including, epicatechin and catechin as well as five procyanidin dimers.
Fermented Java 1 beans had the highest concentration of polyphenols before roasting, followed by Java 2 and Ivorian beans respectively.
The unroasted beans from all origins had an average of 4.82 mg/g epicatechin and 0.26 mg/g catechin.
Epicatechin goes down; catechin goes up
The researchers found that roasting lowered the epicatechin content in all bean origins analysed, but increased the catechin content.
For example, at the strongest roasting temperature (160°C for 30 mins), the epicatechin content in Java 1 beans fell 68%, but the catechin content grew 240%. Certain procyanidin dimers also rose, while others fell.
Ivorian beans registered even larger increases in catechin content with a 836% rise on average across all temperatures measured.
Roast below 140°C to preserve flavanols
Higher temperatures were also said to cause loss of flavanols.
“According to our results, temperature should be kept below 140 °C in order to preserve most of the initial flavanol concentration and to obtain almost unaffected flavanol composition,” said the researchers.
Other cocoa flavanol research
An earlier study by Crozier et al. showed that dry fermented cocoa beans contain 6-7% of polyphenolic content by weight.
Previous research by Elwers et al. found that cocoa bean fermenting reduced the initial concentration of flavanols by around 90%.
During a site visit earlier this year, Barry Callebaut revealed that the presence of cocoa flavanols varied depending on the origin of the bean - with Central and South American origins having the highest concentrations due to the soil, the climate and the strain of beans
Food Chemistry, Vol. 141, Issue 4, p 3656–3663
‘Temperature influences epimerization and composition of flavanol monomers, dimers and trimers during cocoa bean roasting’
Authors: Lisa Kothe, Benno F. Zimmermann, Rudolf Galensa