Search

• Cacao bean incubation reveals that fermentation can reduce nib Cd content. • Reduction of nib Cd was most pronounced at high temperature and low pH. • Nib Cd mobilisation during fermentation is likely related to phytate breakdown. Earlier studies revealed that cadmium (Cd) concentrations in cacao nibs can decrease by a factor up to 1.3 during fermentation. Here, fermentation was mimicked by incubating beans at different temperatures, and acetic acid and ethanol concentrations in the incubation media. Nib Cd concentrations decreased during incubation by mobilisation in the nibs and subsequent outward migration to the testa and the incubation solution. This was most pronounced when high concentrations of acetic acid were combined with high temperature, while ethanol had no statistically significant effect. Incubation under typical fermentation conditions (45 °C and 20.0 g acetic acid L−1) reduced the nib Cd concentration by a factor 1.3. This factor increased to 1.6 under more extreme conditions, i.e. 65 °C and 40 g acetic acid L−1. The final nib Cd concentrations correlated well to nib phytate concentrations (R2 = 0.56), suggesting hydrolysis of phytate and mobilisation of the associated Cd2+. [ABSTRACT FROM AUTHOR]

Previous work has shown that cacao nib cadmium (Cd) concentrations decrease during fermentation, but only when reaching sufficiently low nib pH. In this work, lab-scale experiments (5 kg units) with lactic and acetic acid amendments were ineffective at reducing the total nib Cd concentration. In contrast, the water-extractable fraction of the nib Cd concentration clearly increased when the pH was decreased. When single pod derived beans were embedded inside a full-scale fermentation box to monitor the effect of the fermentation effect with high precision, nib Cd concentrations decreased by a factor 1.25 (P-value <0.05) after four days of fermentation. Visualisation of the mobile Cd gradient within beans with LA-ICP-MS (using imprints of transversal cuts exposed to a metal binding gel) revealed that fermentation enhances the Cd mobility in the nibs. • Fermentation induces outward migration of Cd from cacao nib to mucilage and testa. • Water extractable Cd in cacao nibs increases with decreasing pH. • Organic acid treatments during lab scale fermentation did not lower nib Cd content. • Mobile Cd gradients within cacao beans were visualized with LA-ICP-MS. [ABSTRACT FROM AUTHOR]