Cadmium speciation in cacao beans changes during a fermentation-like incubation

Area of Science:

• Agricultural Science
• Food Chemistry
• Environmental Science

Background:

• Cadmium (Cd) contamination in cacao beans frequently surpasses established food safety limits.
• Cacao bean fermentation is a critical step that influences the chemical composition and quality of chocolate.
• Previous research indicates fermentation increases Cd solubility, suggesting a potential mitigation strategy for Cd in cacao products.

Purpose of the Study:

• To investigate the specific changes in cadmium speciation during cacao bean fermentation.
• To understand the mechanisms behind Cd migration and transformation during the fermentation process.

Main Methods:

• Utilized X-ray absorption spectroscopy (XAS) to analyze Cd speciation.
• Employed speciation calculations to interpret spectroscopic data.
• Conducted fermentation-like incubations on cacao beans from high and low Cd-contaminated farms, simulating high temperatures (>45°C) and acidic pH (<5).

Main Results:

• Incubation reduced Cd concentration in cacao nibs by up to 1.5 times.
• In high Cd beans, fermentation shifted Cd complexation from sulfur to oxygen ligands, likely due to pH changes.
• In low Cd beans, Cd remained complexed with oxygen ligands both before and after incubation.
• Observed migration of Cd outward from the nib, potentially driven by pH changes and/or phytate breakdown.

Conclusions:

• XAS and speciation calculations are complementary techniques for analyzing Cd speciation changes.
• Fermentation significantly alters Cd complexation and can reduce overall Cd concentration in cacao beans.
• Understanding Cd speciation during fermentation offers pathways for mitigating heavy metal contamination in cacao products.