Effect of cacao bean quality grade on cacao quality evaluation by cut test and correlations with free amino acids and polyphenols profiles.

Cacao fermentation induces biochemical changes in the beans that lead to different cacao grades such as slaty (unfermented), violet (under fermented) and brown (fully fermented) beans. This grade heterogeneity in a sample set can impact the quality of the end-products. In the present study, amino acids and polyphenol contents of slaty, violet and brown beans were evaluated. Free amino acids were derivatized from o-phthalaldehyde and detected with a fluorescence spectrophotometer coupled with a reverse phase HPLC system. Polyphenols were analysed at 280 nm by HPLC using a Photodiode Array Detector. Amino acids content in the violet beans were significantly higher (11,165 ± 4281 mg kg-1 fat free dry material, ffdm) than that of the slaty beans (4304.5 ± 1927.6 mg kg-1 ffdm), meanwhile there was no significant difference between violet and brown beans. Epicatechin, catechin, cyanidin-3-arabinoside and cyanidin-3-galactoside contents were significantly lower in violet and brown beans when compared to slaty beans. Our results have shown that a mixture of violet and brown beans is suitable to obtain polyphenols and amino acids in the development of cacao products.