Stable Radical Content and Anti-Radical Activity of Roasted Arabica Coffee: From In-Tact Bean to Coffee Brew

Abstract

The roasting of coffee beans generates stable radicals within melanoidins produced by non-enzymatic browning. Roasting coffee beans has further been suggested to increase the antioxidant (AO) capacity of coffee brews. Herein, we have characterized the radical content and AO capacity of brews prepared from Coffea arabica beans sourced directly from an industrial roasting plant. In-tact beans exhibited electron paramagnetic resonance signals arising from Fe3+, Mn2+ and at least three distinct stable radicals as a function of roasting time, whose intensity changed upon grinding and ageing. In coffee brews, the roasting-induced radicals were harboured within the high molecular weight (> 3 kD) melanoidin-containing fraction at a concentration of 15 nM and was associated with aromatic groups within the melanoidins. The low molecular weight (< 3 kD) fraction exhibited the highest AO capacity using DPPH as an oxidant. The AO activity was not mediated by the stable radicals or by metal complexes within the brew. While other non-AO functions of the roasting-induced radical and metal complexes may be possible in vivo, we confirm that the in vitro antiradical activity of brewed coffee is dominated by low molecular weight phenolic compounds.

EPR Methods Applied on Food Analysis

“…An example of the use of Mn II X-band EPR spectroscopy for the discrimination of Cypriot wines from various grape varieties is shown in Figure 3 (unpublished results). In addition to the characteristic shape of the spectrum, the quantity of Mn II in each wine can be measured from the double-integrated spectra in the presence of standard [14,16] information that can be additionally used as a variable for the wine discrimination.…”

Ochratoxin A, fungal contamination and antioxidant property of defective Arabica coffee in Benguet, Philippines

“…Based from the results presented in Table 1, non-defective green coffee beans had the highest total phenolic compounds to defective green coffee beans and the roasted coffee samples. Troup et al (2015) reported that low molecular weight polyphenolic compounds contributed greatly to the antioxidant activity of coffee brews. In addition, the antioxidant property of green coffee bean extracts is chlorogenic acid (Chachurin et al, 2002;Ramalakshmi et al, 2007;Ramalakshmi et al, 2009;Jeszka-Skowron et al, 2016).…”

“…The metal chelating activity of coffee bean extracts has been attributed to the contribution of low-molecular weight phenolic compounds (Gornas et al, 2016), caffeic acid (Generato-Mattos et al, 2015) and melanoidins (Vignoli et al, 2011;Troup et al, 2015). While metal chelating activity shows an increasing trend relative to the total phenolic compounds in green coffee beans, this was not observed in roasted coffee samples.…”

“…This explains why roasted coffee samples had lower total phenolic content compared to green coffee bean samples. However, roasting also promotes the formation of several compounds such as melanoidins due to caramelization and Maillard reactions (Chachurin et al, 2002;Franca et al, 2005b;Troup et al, 2015), and melanoidin-like compounds which forms polymers with sugars, amino acids and other remaining phenolic compounds (Takenaka et al, 2005). Roasting coffee beans increase the formation of other antioxidants compared to the loss of phenolic compounds (Vignoli et al, 2011;Opitz et al, 2014) thereby compensating the loss of antioxidant activities during roasting (Liang & Kitts, 2014).…”

Investigation of the modulatory role of Bulgarian Mentha Piperita L. oil against radiation-induced oxidative disorders and antioxidant status In Vitro

“…The usage of in vitro and in vivo model systems, serve as models for preliminary observations in the evaluation of pharmacological activities, radiation-induced oxidative changes in chemical composition and different EPR spectrum shapes as a function of temperature and time [23,25,26].…”