Antioxidant Generation during Coffee Roasting: A Comparison and Interpretation from Three Complementary Assays

Abstract

Coffee is a major source of dietary antioxidants; some are present in the green bean, whereas others are generated during roasting. However, there is no single accepted analytical method for their routine determination. This paper describes the adaption of three complementary assays (Folin-Ciocalteu (FC), ABTS and ORAC) for the routine assessment of antioxidant capacity of beverages, their validation, and use for determining the antioxidant capacities of extracts from coffee beans at different stages in the roasting process. All assays showed a progressive increase in antioxidant capacity during roasting to a light roast state, consistent with the production of melanoidins having a higher antioxidant effect than the degradation of CGAs. However, the three assays gave different numbers for the total antioxidant capacity of green beans relative to gallic acid (GA), although the range of values was much smaller when chlorogenic acid (CGA) was used as reference. Therefore, although all three assays indicated that there was an increase in antioxidant activity during coffee roasting, and the large differences in responses to GA and CGA illustrate their different sensitivities to different types of antioxidant molecule.

Evaluation of Antioxidant and Anti-Aging Efficacies of Coffea Robusta Extract on Human Fibroblast

“…This result showed that the anti-oxidant activity of coffee extract is in concentration-dependent manner. Moreover, Coffea robusta extract has stronger anti-oxidant efficacy after roasting, similar with previous study results [3,4,7]. …”

Understanding the Effects of Roasting on Antioxidant Components of Coffee Brews by Coupling On‐line ABTS Assay to High Performance Size Exclusion Chromatography

“…The observation of the lowest concentration of CGA in dark/slow roasts also indicates that lower temperatures over a longer time span have a higher impact on CGA degradation than short roasting at higher temperatures. Furthermore, LMW compounds are already prone to degradation at very early stages of the roasting process and the highest antioxidant activities are observed at even lighter roast degrees (Opitz et al , ). In addition to incorporation of CGAs in melanoidins, many other new compounds with antioxidant capacity are generated during roasting, especially structural isomers of CGAs (van der Werf et al , ).…”

“…We have previously reported results which suggest that the time–temperature history (Smrke et al , ), O 2 exposure during cooling/quenching (Goodman et al , ), and the coffee species (Opitz et al , ), all have significant impacts on antioxidant or free radical products of the beverage. However, the simple conduct of batch assays is inadequate for evaluating the contributions of various compounds to measured antioxidant values (Kusznierewicz et al , ; Celik et al , ).…”

“…del Castillo et al , ; Cämmerer and Kroh, ), but the use of different methods/assays makes it difficult to find a consistent interpretation of the various results (Vignoli et al , ). In most cases batch assays are used to characterise various coffee brews, even though the values depend also on the choice of reference standard (Opitz et al , ).…”

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

“…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). This may explain why the radical scavenging activity and metal chelating activity of both non-defective and defective coffee beans increased even if their total phenolic content decreased after roasting.…”