Rapid screening of unground cocoa beans based on their content of bioactive compounds by NIR spectroscopy

Abstract

Near Infrared (NIR) spectroscopy was evaluated as a fast and easy method for identifying the most interesting cocoa genotypes according to chemical composition, including bioactive compound contents, in more than 80 samples of cocoa beans from the Mexican Germplasm Bank, which were harvested over three years. Clear differences in chemical composition were detected in fermented and dried samples among genotypes. The contents in fat, protein, total sugars, total phenols, phenolic compounds and theobromine were determined for both whole cocoa beans and ground cotyledon samples; and calibration models were developed from the spectra of intact beans, nibs and ground cotyledons. In general, the calibration models obtained for cotyledon composition from the spectra of cocoa nibs and ground beans were better than those obtained from the spectra of intact beans. Fat content showed better calibration statistic values from the spectra of nibs and ground cotyledon (r2 = 0.70). Bioactive compounds, such as theobromine (r2 = 0.77), total sugars (r2 = 0.74), total phenols (r2 = 0.66) and derivatives of epicatechin (r2 = 0.88), together with fat (r2 = 0.70), protein (r2 = 0.64) and husk content (r2 = 0.82), were well-predicted using NIR spectroscopy in intact beans, cocoa nibs and/or ground cotyledon. The potential of NIRS technology was confirmed to support germplasm banks and breeding programs for the rapid identification of interesting genotypes based on their contents in bioactive compounds.