Comparación de los niveles de cadmio en cacao tipo nacional en la parroquia Río Bonito, provincia de el Oro-Ecuador

Abstract

The high cadmium (Cd) content in cocoa tissues and soils has shown great concern in the consumption of chocolates and derivatives, leading to food safety agencies imposing a critical level (NC) on both soils and cocoa beans (0.5 mg/kg). Some researchers have demonstrated in their studies that the soils and tissues of Ecuadorian cocoa have high levels of this heavy metal exceeding the NC, being the coastal region the most affected. The investigation had as objective to determine the levels of cadmium present in leaves, testa and almond of cocoa in the genotypes National and Collection Castro Naranjal Tree 51 (CCN51), located in the parish Rio Bonito (El Guabo, El Oro). Two cocoa farms were selected: F1 (National) and F2 (CCN51); where three plants were taken at random from which the vegetative tissues were extracted (leaf, shell, almond) for subsequent analysis in the laboratory by acid digestion and reading with the atomic absorption spectrophotometer; additional soil samples were collected in the study farms (n = 2), to know the current nutritional status of the sites. Descriptive statistical analyses were performed (mean, standard deviation, maximum and minimum values), Pearson correlation (soil chemical properties, nutritional elements, cocoa tissues), T-test considering (P > 0.05). pH levels ranged from F1 5.25 to 4.47 F2 being an indicator of the presence of Cd. MO (%) values in F1 were higher (3.35 %) than F2 (2.75 %). The contents of CE varied according to F1 0.11 dS/m to 0.16 dS/m F2 being within the optimal levels in both sites (< 1 dS/m). As for the nutritional elements in the soil there is an imbalance (low, medium, high), causing the plant to absorb the Cd and accumulate it in its tissues; the absorption rate of this heavy metal (Cd) is related to the deficiencies of Zn and Mn due to the fact that they are in competition for the proteins transporting the cell membranes in the root and foliar tissues of the plant. The levels of Cd analyzed in the farms of study reflected variations in the contents of leaf, F1 0.36 mg/kg and in F2 2.59 mg/kg; in the almond there were few statistical differences within the sites F1 1.93 mg/kg and F2 1.21 mg/kg; in the testa the F1 evidenced greater concentration 4.00 mg/kg while in the F2 3.30 mg/kg. The results showed negative (pH/leaf) and positive (pH/almond) correlation. In the case of nutritional elements, significant correlations were presented (NH4-Ca-B), due to the few samples analyzed per farm, studies should be made with a greater number of samples. The contents of Cd in the sites presented values that are above the maximum permissible limit (LMP), presenting the highest levels in the shell, followed by almonds. It is recommended to look for viable mitigation alternatives to reduce Cd contents in soils and tissues.