Abstract:
Cocoa (Theobroma cacao L.) beans are a key ingredient in food industries. Cocoa provides
great economic support for the farmers in the producing countries. There has been increasing
interest in bioactive components of cocoa beans as they are related to the nutritional and
sensory quality of cocoa products. This study aims to fill the gaps in the current knowledge of
natural bioactive components in cocoa beans, especially phenolics, and their dynamic as the
effect of genetics related to the post-harvest treatment.
The effect of intravariety diversity on the bioactive components of the cocoa beans was studied
on Sulawesi 1 (Sul 1) cocoa beans (Trinitario variety) with different degrees of fermentation.
The bean samples were collected from Indonesia. There was a wide variation in concentrations
of bioactive compounds among the beans. These cocoa beans can be categorized into four
distinct groups based on the profiles of flavan-3-ol derivatives, phenolic acids, flavonols, and
anthocyanins. The fermentation index of cocoa beans could not be directly related to the
phenolic profile.
The bioactive compounds in 26 cocoa beans genotypes from Indonesia were identified and
quantified. The results showed great diversity in the composition of bioactive compounds
among different genotypes. The concentrations of methylxanthines, epicatechin,
proanthocyanidin B-type oligomers, clovamide, and anthocyanins were important variables
that differentiated these genotypes. MCC 01, SUL 3, ICCRI 03, and ICS 60 genotypes had the
highest contents of flavan-3-ols, including proanthocyanidin, and could be developed for
“healthy” product formulations. Some genotypes such as DR 1, DR 2, DR 38, ICS 13, KPC 1,
KW 617, RCC 71, and TSH 858 could be favored by industries due to the potential to be made
into end-products with a brighter appearance.
The study of the dynamic of bioactive components in the Sul 1 cacao genotype during
fermentation was carried out. The first 48 h of fermentation significantly determined the
composition of the methylxanthines and phenolics in the cocoa beans. The prolonged
fermentation (> 96 h) period did not further reduce the contents of methylxanthines and
phenolics in the cocoa beans. Important volatiles characteristic of cocoa/chocolate flavor was
mostly developed after 48 h of fermentation. The fermentation for 72 h retained considerable
amounts of methylxanthines and phenolics in the beans while producing cocoa beans with high
chocolate aroma attribute and less bitterness and astringency.
Twenty-two cocoa bean samples were collected from different geographic origins of
Indonesia. These samples were dried cocoa beans currently sold by farmers and collectors in
respective areas of samples collection. The results revealed great diversity in the chemical
composition of these beans. Unfermented cocoa beans were rich in methylxanthines and
phenolics but had low amounts of key odorant volatiles. Fermented samples shared similar
characteristics (less bioactive compounds and abundant key odorant volatiles) regardless of
their geographic origins. The origins of the samples could not be determined using the results
of bioactive compounds and key odorant volatiles due to the influence of post-harvest
processing. Separation of samples based on their fermentation degree (under-fermented and
fermented samples) during PCA improved the accuracy of the determination of geographic
origins. The origin of cocoa beans could be delineated by PCA using mineral composition data
of the fermented samples.
A study on the underutilized cocoa genotypes was carried out on T. grandiflorum, T. bicolor,
and T. subincanum. The bioactive components and flavor volatiles of different bean genotypes
of these species were profiled and compared with those of T. cacao. T. grandiflorum and T.
bicolor had different profiles of methylxanthines and phenolics from T. bicolor and T. cacao.
T. grandiflorum and T. subincanum were rich in theacrine and flavones. T. grandiflorum, T.
bicolor, and T. subincanum beans generally had less phenolics than T. cacao. Roasting
decreased the concentrations of methylxanthines and phenolics in the beans. Roasted T.
grandiflorum and T. subincanum beans had higher concentrations of pyrazines and esters than
T. cacao. T. grandiflorum and T. subincanum beans had high flavor potential with more
complex and richer sensory profiles than T. cacao. Overall, the underutilized Theobroma
species have the potential to be exploited to improve the nutritional and flavor quality of cocoa
products.