Relationships between Cadmium in Tissues of Cacao Trees and Soils in Plantations of Trinidad and Tobago

Abstract

The primary source of cadmium in cocoa beans has been linked to its direct uptake by the cacao plant from cadmium contaminated soils. This research was conducted to evaluate and interpret significant relationships between cadmium levels in tissues of the cacao plant and soils from cocoa-growing areas in Trinidad and Tobago. Total (HNO3-extractable) concentrations of cadmium in both tissues and soils were determined. The levels of cadmium measured varied in the order: leaves > pods > shells > nibs > soil. Cadmium levels in all the cacao tissues analyzed were significantly (p < 0.05), positively and strongly correlated with each other. Additionally, significant (p < 0.05) positive relationships were also identified between Cd in cacao tissues and corresponding total HNO3-extractable Cd levels in soils. These findings suggest that they can possibly be used as predictive tools for assessing Cd levels in cacao.

The impact of fermentation on the distribution of cadmium in cacao beans

“…Considering the average weight fractions for nib (0.93) and testa (0.07), 91% of the total bean Cd was located in the nib and 9% in the testa in unfermented cacao beans. In accordance to the present work, Ramtahal et al (2016) reported significantly higher Cd concentrations in testa (0.44-4.41 mg Cd kg -1 ) compared to nibs (0.35-3.82 mg Cd kg -1 ) for unfermented cacao beans from Trinidad and Tobago. Lewis et al (2018) reported more than two-fold higher Cd concentrations in the testa (average 1.83 mg kg -1 ) compared to those in the nibs (average 0.88 mg kg -1 ) for unfermented cacao beans from the same genetic group and grown in a common garden.…”

“…Gramlich et al (2018) measured the Cd concentration in cacao from 55 farms in Honduras and did not find a significant difference between the Cd concentration in the pod husks (1.1 ± 0.2 mg kg -1 ) and that in the nibs (1.1 ± 0.1 mg kg -1 ). Conversely, Ramtahal et al (2016) reported higher Cd concentrations in the pod husks (0.53-4.49 mg Cd kg -1 ) compared to the nibs (0.35-3.82 mg Cd kg -1 ) for cacao from 45 farms in Trinidad and Tobago.…”

“…The Cd concentration in the testa is generally reported to be higher than in the nibs. For example; Lewis et al (2018) found more than twofold higher Cd concentrations in the testa compared to the nib, and Ramtahal et al (2016) reported higher Cd concentrations in the testa compared to the nib in cacao from Trinidad and Tobago. The reverse has also been observed.…”

“…Chavez et al (2015) measured the Cd concentrations in cacao from 19 Ecuadorian farms and generally found higher Cd concentrations in the nib compared to the testa. Sample treatment often differs, cacao samples were provided by chocolate manufacturers with little information regarding sample processing (Lee & Low, 1985), samples were either or not washed with water which can affect Cd concentrations in the outer tissues (Gramlich et al, 2018;Lewis et al, 2018;Ramtahal et al, 2016), or samples were washed with chelating agent solutions (Chavez et al, 2015). To the best of our knowledge, the influence of fermentation on the Cd distribution in cacao has not been reported to date.…”

Cadmium isotope fractionation in the soil – cacao systems of Ecuador: a pilot field study

“…Such work has shown that there are large regional variations of Cd levels in cacao beans, whereby problematically high concentrations are particularly prominent in Latin America and some Asian countries. [4][5][6][7][8][9][10][11][12][13] In these regions, the Cd concentrations of beans commonly exceed 0.6 to 0.8 mg kg À1 , 14 which is the approximate upper range for manufacturing cocoa products that are in accord with the new EU regulations. 8,15 For example, a recent study of more than 500 farms in Ecuador revealed that nearly 50% of the cacao beans had Cd concentrations that exceeded 0.6 mg kg À1 .…”