Effect of in vitro digestion-fermentation on green and roasted coffee bioactivity: The role of the gut microbiota
Introduction
Coffee is the food product most consumed in the world after water (Farah & Ferreira dos Santos, 2015). Coffee has been related to health since ancient times and still today is studied frequently in many research projects related to chronic diseases (Galluzzi Bizzo, Farah, Ann Kemp, & Berguinins Scancetti, 2015). The protective role of coffee on health is thought to be mostly related to its high antioxidant capacity and is also linked to its high consumption (Saura-Calixto & Goñi, 2006). Coffee brews have a wide range of antioxidant compounds such as different types of phenolics (hydroxycinnamic acids such as caffeic, ferulic, coumaric and chlorogenic acids), aromatic compounds and Maillard reaction products such as melanoidins (Pastoriza & Rufián-Henares, 2014). Polyphenols have been reported to exert a protective role against several diseases such as cardiovascular or neurodegenerative diseases and cancer thanks to their ability to protect cells against oxidation (Galluzzi Bizzo et al., 2015). Further, 5-caffeoylquinic acid (a chlorogenic acid) has been shown to have a protective role against neurodegenerative diseases (Jeszka-Skowron, Stanisz, & De Peña, 2016). Melanoidins which are produced during roasting process, are also potent antioxidants (Jiménez-Zamora, Pastoriza, & Rufián-Henares, 2015).
During the roasting step, most of the aromatic compounds of coffee are generated while others are affected (mostly chlorogenic acids) by the heat treatment. During this process, some other compounds (like melanoidins or quinic acid) appear, which contributes to coffee’s antioxidant capacity (Ludwig, Bravo, De Peña, & Cid, 2013). Generally, the main changes in composition involve loss of polysaccharides, oligosaccharides, chlorogenic acids, and trigonelline (Gniechwitz, Reichardt, Blaut, Steinhart, & Bunzel, 2007). Moreover, the lactones of the chlorogenic acids are formed during roasting, but such formation depends on the degree of roasting.
Dietary polyphenols are mostly utilized by the gut microbiota, since most escape digestion and have low absorption rate in the small intestine (Selma, Espín, & Tomás-Barberán, 2009). Phenolic compounds feed the human gut microbiota, and microbial metabolites of polyphenols are absorbed in the large intestine and reach the blood stream (Russell & Duthie, 2011). It has been reported that coffee is able to change some microbial communities and modify the end-products of community metabolism (Cowan et al., 2014). On the other hand, roasted coffee is also able to modify the gut microbiota due to the high content of melanoidins, which can behave as fiber-like compounds in the gut (Jiménez-Zamora et al., 2015).
Taking all this information into account, green and roasted coffee could be considered as two different products due to the different chemical composition they have, which in turn will shape the composition and functionality of the gut microbiota. Therefore, the aim of the present paper is to unravel the differences between green and roasted coffee after in vitro digestion-fermentation process. To do that, the differences in antioxidant capacity, individual polyphenols and gut microbiota structure of digested-fermented extracts of three green and roasted coffees from different locations were studied.
Section snippets
Chemicals
Trolox ((±)-6-Hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid), 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, 2,4,6-Tri(2-pyridyl)-s-triazine (TPTZ), potassium persulphate, 3,5-dicaffeoylquinic acid, caffeic acid, dimethyl caffeic, chlorogenic acid, ferulic acid, coumaric acid, gallic acid, tyrosol, p-hydroxybenzoic acid, m-hydroxyphenylacetic acid, acetic acid, propionic acid, butyric acid, Folin-Ciocalteu reagent, sodium hydroxide, hydrochloric acid, iron (III)
ABTS assay
The antiradical antioxidant capacity of coffees measured with the ABTS assay showed values in the same range for the regular coffee brew, digested and fermented coffee brews (Fig. 1A). Regular coffee brews had values ranging from 18.1 to 30.1 mmol Trolox equivalents/L for BA and VRR, respectively. In general, undigested coffee brews obtained from roasted coffees were statistically more antioxidant (p < 0.05) than their respective green coffees, with an exception of Brazilian coffee. The effect
Conclusions
This manuscript reports the effect of in vitro digestion-fermentation of green and roasted coffees on the antioxidant capacity, phenolic profile, SCFAs production and microbial community structure. In many cases, roasted coffee brew showed higher antioxidant values than green coffees. Moreover, in FRAP and Folin-Ciocalteu assays, digested coffee brews displayed significantly higher values than regular coffee brews, and even higher values were obtained for fermented coffees. On the other hand,
Acknowledgements
This study was supported by project AGL2014-53895-R from the Spanish Ministry of Economy and Competitiveness and by the European Regional Development Fund (FEDER) and by the National Science Foundation award DBI-1335772 to OP. This paper will form part of the doctoral thesis by Sergio Pérez-Burillo, conducted within the context of the “Nutrition and Food Sciences Programme” at the University of Granada. We are thankful to Denise Kramer for her assistance with high-throughput sequencing.
Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Conflict of interest
The authors declare that there is no conflict of interest regarding the publication of this paper.
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