## 1 Introduction  
Coffee is one of the most favored beverages in the world. The production of coffee beans in 2018/19 reached 170.22 million bags, 4.6% higher than in 2017/2018 [1]. A national survey in the United States shows that 75% of adults drink coffee, and 49% drink more than one cup daily [2]. Coffee consumption has beneficial effects on lowering the risk of Parkinson's disease, Alzheimer's disease, cardiovascular disease, type 2 diabetes mellitus, and liver cirrhosis [3]. These health-improving properties of coffee are related to its antioxidant content [3]. There are about 700 or more chemical compounds in coffee extracts [4]. Studies have reported that the antioxidant activity of coffee is attributed to phenolic compounds, mainly chlorogenic acids, and other compounds such as caffeine, tocopenroels, or Maillard reaction products [5, 6]. This bioactive concentration in coffee depends on many factors, such as origin, roasting, and brewing methods.  
Coffee roasting is the process of producing coffee flavors by applying heat over 200 \({}^{\circ}\)C to green beans [7]. As the roasting progresses, temperature rise, moisture evaporation, volume increase, and dry matter decrease occur inside coffee beans, thereby roasting is one of the pivotal factors in determining coffee quality [7]. Coffee extraction refers to dissolving the soluble components of ground coffee beans in a liquid solvent [8]. The extracting procedure influences the composition of the final coffee extract. Significant differences are found in polyphenol extraction, caffeine content, total solids, antioxidant activity, and volatility profile [9]. Espresso and drip extraction is the most commonly used method of coffee brewing [10]. The espresso method applies pressure above atmospheric pressure to the ground coffee beans [8]. In a drip method, coffee beans are ground into a powder, passing water through it and filtering the coffee extract simultaneously [10].  
The antioxidant capacity of coffee extracts depends on coffee varietals and their extraction method [11,12]. However, previous studies on roasting degree and antioxidant capacity have mainly focused on coffee extracts of unknown species in local markets. Additionally, little has been reported on whether the effect of roasting degree on the antioxidant properties of coffee is the same for espresso and drip coffee. In a previous study, the amount of total phenolics and DPPH radical scavenging activity of early-roasted Java coffee bean powder have been reported [13]. However, the effect of roasting degrees on the antioxidant properties of _Coffea arabica_ cv. Java coffee prepared by espresso and drip methods has not been studied yet. Several methods have been established for the determination of the antioxidant activity of plants. In addition, several analytic methods have been developed for its determination. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP), and Trolox equivalent antioxidant capacity (TEAC) are generally used techniques to evaluate antioxidant properties in vitro. However, it has been reported that the results of these analyzes are different and not correlated in some materials. Therefore, we aimed to investigate the effect of roasting degree on the antioxidant properties of espresso and drip coffee prepared using _Coffea arabica_ cv. Java. This study applied various antioxidant assays to espresso and drip coffee with various degrees of roasting and statistically analyzed relationships among the variables.