Abstract
Analysis of pulp and peels of Arabica coffee varieties with different external fruit color allowed the identification of 16 phenolic compounds using high-performance liquid chromatography with diode array detection and electrospray ionization multiple-stage mass spectrometry (HPLC-DAD-ESI-MSn). Nine chlorogenic acids, three flavan-3-ols, the xanthone mangiferin, the flavonol rutin and two anthocyanins were tentatively identified and quantified. 5-O-Caffeoylquinic acid together with a putative (epi)catechin hexoside were the predominant phenolics detected in the coffee varieties analyzed in this work. Whereas 3- and 4-caffeoylquinic acids, as well as 5-O-feruloylquinic acid were consistently found in higher quantities in the pulp than in the peels when individual varieties were compared, the opposite was found for the other phenolic compounds detected. Complementary, GC-MS after alkaline hydrolysis and trimethylsilylation permitted the identification of more than 30 constituents, including phenolic compounds and other benzenoids, caffeine, and diverse carboxylic acids. Detected anthocyanins were cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside. Anthocyanin contents in orange-colored berries were lower than those in red fruits, while no anthocyanins were found in yellow-colored fruit. Among non-anthocyanin pigments, we found β-carotene and lutein in all varieties, along with other chloroplast-specific carotenoids in some accessions. In addition, saponification evidenced the presence of several xanthophyll esters. Both, chlorophyll a and b, were detected in the peels of all varieties, while only chlorophyll b was observed in the pulp. Thus, the color of yellow-peeled varieties is due to carotenoids, while that of orange and red-peeled varieties is due to both carotenoids as well as low and high levels of anthocyanins, respectively. Present results point out to the potential use of by-products of particular coffee varieties with differences in the external fruit color as a source of distinctive bioactive compounds, including anthocyanins and carotenoids, with health benefits.
Highlights
By-products accruing during coffee processing represent more than 50% of the coffee fruit dry weight (Esquivel and Jiménez, 2012)
The anthocyanins cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside have been described (Prata and Oliveira, 2007), for which potential culinary applications have been proposed (Parra-Campos and Ordóñez-Santos, 2019). Their contents have been only analyzed in whole berries of coffee, without separating the different fractions, and their accumulation was associated with the expression of carotenoid biosynthetic genes (Simkin et al, 2010)
Aiming at increasing evidence about the potential use of coffee by-products as source of bioactive compounds, in this study we employed up-to-date analytical methods to characterize the phenolic compounds, including anthocyanins, as well as carotenoids in peels and pulp of five Costa Rican coffee (Coffea arabica L.) varieties growing at the same farm under the same agro-ecological conditions
Summary
By-products accruing during coffee processing represent more than 50% of the coffee fruit dry weight (Esquivel and Jiménez, 2012). In contrast to dry coffee processing, the wet procedure usually allows the recovery of non-degraded peels and pulp (Esquivel and Jiménez, 2019), a very interesting source of valuable bioactives, whose identification and quantification have sluggishly started to promote their utilization for nutritional and pharmaceutical purposes. Taking advantage of these by-products will certainly benefit from further studies and from the development of new methodologies to improve their extraction (Esquivel and Jiménez, 2012; Heeger et al, 2017; Saini and Keum, 2018; Torres-Valenzuela et al, 2020). Aiming at increasing evidence about the potential use of coffee by-products as source of bioactive compounds, in this study we employed up-to-date analytical methods to characterize the phenolic compounds, including anthocyanins, as well as carotenoids in peels and pulp of five Costa Rican coffee (Coffea arabica L.) varieties growing at the same farm under the same agro-ecological conditions
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