A study published in the African Journal of Food, Agriculture, Nutrition and Development found that storing cocoa pods for seven days prior to fermentation led to higher antioxidant activity after beans had been roasted.
It also discovered cacao beans that had been roasted at a lower than normal temperature and for a longer time of 45 minutes exhibited higher antioxidant activity.
Pod storage boost
"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 lead author Emmanuel Ohene Afoakwa of the University of Ghana.
His team separated 300 pods into four groups: some pods were stored for three days, others for seven or 10 and some not at all.
After this ‘pulp preconditioning’ phase - in which pods were stored at ambient temperature - fermentation and drying were conducted as usual.
Afoakwa found seven day storage resulted in the highest antioxidant activity after roasting.
He said storage allowed the sweet pulp surrounding the beans to alter biochemical and physical constituents of the beans.
“This aided the fermentation processes and enhanced antioxidant capacity of the beans, as well as the flavor," said Afoakwa.
His team also experimented with roasting times. They roasted cacao beans at various temperatures for different lengths of times.
Afoakwa said cacao beans are typically roasted for 10-20 minutes at 120 - 130°C, but by roasting for 45 minutes at 117°C this slower process at a lower temperature increases the antioxidant activity.
Beans stored and then roasted for 45 minutes have more polyphenols than those not stored, the team found. The storage phase is also suspected to reduce bitterness of the beans.
Afoakwa said the findings could benefit cacao beans from Southeast Asia and Latin America, which usually produce chocolate with a less intense chocolate flavor and with reduced antioxidant activity.
Next moves and other research
In future, his team plans to get a better understanding on how roasting impacts the flavor of freshly picked compared to stored cocoa beans.
The study was backed by the Belgium Government under the VLIR TEAM Cocoa Project between Ghent University and the University of Ghana.
A 2013 study by Universiti Sains in Malaysia said superheated steam roasting retained more phenols and flavonoids during cocoa processing than the conventional roasting.
Barry Callebaut - which produces flavanol preserving chocolate under its Acticoa process - previously told this site that cacao beans from Central and South America had the highest cocoa flavanol levels globally due to the soil, climate and the strain of beans.
African Journal of Food, Agriculture, Nutrition and Development - Vol 15, No 1 (2015)
‘Roasting effects on phenolic content and free-radical scavenging activities of pulp pre-conditioned and fermented cocoa (Theobroma cacao) beans’
Authors: E O Afoakwa, E Ofosu-Ansah, A S Budu, H Mensah-Brown, J F Takrama