Big differences in cocoa flavanol losses during roasting

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

Source:
Food Chemistry,​ Vol. 141, Issue 4, p 3656–3663
http://dx.doi.org/10.1016/j.foodchem.2013.06.049​
‘Temperature influences epimerization and composition of flavanol monomers, dimers and trimers during cocoa bean roasting’​
Authors: Lisa Kothe, Benno F. Zimmermann, Rudolf Galensa