Correlation between color parameters and bioactive compound content during cocoa seed transformation under controlled process conditions

Abstract

The quality demanded by consumers in the cocoa sector has led to carrying out the postharvest transformation of cocoa, directing efforts to highlight properties of cocoa beans, such as the content of bioactive compounds, due to its beneficial effects on health, as well as its color, which varies from the typical brown color to the recently developed red-pink hues. This work aims to establish a correlation between the color parameters of a cocoa matrix obtained during the transformation of cocoa seeds under controlled process conditions (temperature, organic acid, and its concentration, and time) and the flavan-3-ols content (catechin, epicatechin, and epigallocatechin), methylxanthines content (theobromine, caffeine), and total phenolic content (TPC) through image analysis of color. The results showed that the content of flavan-3-ols and methylxanthines decreased as the controlled transformation advanced. However, the content of these bioactive compounds is retained by applying mild temperature conditions (30 °C) and low concentrations of organic acid (1 g/L) to transform cocoa seeds. Furthermore, the color parameters respond to changes in the internal pH of the seeds, and the red-pink hues are favored when using high concentrations of organic acid (30 g/L). Based on these findings, it was possible to establish a correlation between epigallocatechin content and four color parameters (a*,b*, hab* and Cab*) through a multiple linear regression model. In this way, color image analysis could be an appropriate alternative to predict the concentration of quality-related compounds in cocoa matrices.