Biochemical Evaluation of Beans from Different Theobroma cacao Accessions from Farmer's Field

The study involved the collection, preparation, and laboratory evaluation of cacao (Theobroma cacao) accessions to determine their biochemical, phytochemical, and mineral compositions. A total of 42 cacao accessions were used, comprising 40 accessions collected from farmers’ plantations established between 2008 and 2010 across three Local Government Areas of Cross River State, Nigeria: Ikom (5 farms), Etung (5 farms), and Boki (10 farms), with two accessions obtained from each plantation. Additionally, two accessions were sourced from seed gardens and multiplication units maintained at the Cocoa Research Institute of Nigeria (CRIN) field genebank in Ajassor.For sample preparation, ripe and healthy cacao pods were harvested, and beans fermented for seven days were obtained from eight pods collected from three stems per accession. Beans from each stem were bulked separately, dried individually, and milled into powder using standard procedures. The three stem-derived samples served as experimental replicates for biochemical analyses carried out at the Department of Pharmacognosy, University of Nigeria, Nsukka.Laboratory analyses included proximate, phytochemical, and mineral determinations. Proximate analysis followed Association of Official Analytical Chemists (AOAC, 1990) procedures to evaluate moisture, protein, crude fat, crude fibre, and ash contents. Moisture content was determined by oven-drying samples to constant weight and calculating weight loss. Crude protein was quantified using the micro-Kjeldahl method involving acid digestion, distillation, titration, and nitrogen conversion to protein using a factor of 6.5. Crude fat was extracted using a Soxhlet apparatus with petroleum ether, while crude fibre determination involved sequential acid and alkaline digestion, drying, ashing, and weight difference calculations. Ash content was obtained by incinerating samples in a muffle furnace at high temperature to estimate total mineral residue.Phytochemical analyses assessed key bioactive compounds including caffeine, flavonoids, alkaloids, tannins, and phytate. Caffeine was extracted through aqueous infusion, removal of tannins using lead acetate, solvent partitioning with chloroform, and confirmation by thin-layer chromatography under ultraviolet light. Flavonoids were quantified spectrophotometrically after charcoal purification and acid treatment. Alkaloids were extracted using acidic ethanol, precipitated with ammonium hydroxide, dried, and weighed gravimetrically. Tannins were determined using the Folin–Denis spectrophotometric method based on absorbance comparison with tannic acid standards. Phytate content was measured through hydrochloric acid extraction followed by spectrophotometric analysis against a phytic acid standard curve.Mineral composition analysis involved acid digestion of powdered samples using nitric and perchloric acids to obtain clear solutions suitable for elemental quantification. Concentrations of essential minerals—calcium (Ca), magnesium (Mg), potassium (K), iron (Fe), and zinc (Zn)—were determined using Atomic Absorption Spectrophotometry (Shimadzu AA-7000) with an acetylene flame.Overall, the methodology combined systematic field sampling with standardized analytical techniques to ensure reliable evaluation of nutritional, phytochemical, and mineral characteristics of diverse cacao accessions grown in Cross River State, Nigeria. The use of multiple accessions, replicated sampling from different stems, and internationally recognized analytical procedures enhanced the accuracy and reproducibility of the study’s biochemical characterization of cacao beans.