# Thermal and Kinetic Properties of Brazilian Coffee Arabica Beans
## 1 Introduction  
Coffee is both one of the most popular drinks and also one of the most important food commodities in the world [1]. Coffee production increases annually, with values reaching 7 million tons in 2010, and over 9 million tons in the 2015/2016 season. The worldwide importance of coffee is mainly due to the unique properties of coffee brews. Coffee beverages are known for their stimulating and refreshing effects on humans, their antioxidant activity and unique, pleasant flavour [2].  
To pull out the best characteristics of each green coffee bean, a roasting process is required. The roasting causes a broad spectrum of physicochemical changes in green coffee beans. Due to the high temperatures used in the process, the moisture present in the coffee beans rapidly expands, causing the destruction of the bean matrix. The newly formed porous structure of the roasted beans induces the release of water and aromatic compounds into the atmosphere [3]. Coffee contains thousands of chemical compounds. Due to the complex chemical composition of green coffee beans, an intricate set of concurring chemical reactions lead to the formation and decomposition of many bioactive compounds. As a result, changes in the physical and sensory properties as well as the bioactive compounds profile occur [2, 4, 5]. The roasting process is responsible for the degradation of polysaccharides [6] and phenolic compounds due to their low thermal stability [7], and the formation of Maillard reaction products that darken the colour of the bean and contribute to its overall antioxidant activity [8]. Both green and roasted coffee beans are also a rich source of fatty acids and triacylglycereros [9, 10]. The fat extracted from coffee beans has several industrial applications, mainly in cosmetics and food [11, 12].  
The thermal analysis of food samples supplies reliable and comprehensive information about the nature of the material or the changes within the material that occur during the processing phases. There are many studies reporting the applications of different techniques of thermal analysis in food sciences [13; 14; 15]. These techniques can be used to evaluate a range of specific properties of the analysed samples such as rheological, thermal or structural. Modulated differential scanning calorimetry (MDSC) provides an insight into the many aspects of the thermal response of materials, especially the glass transition. MDSC, through the application of a sinusoidal cooling or heating signal to a sample, measures the reversing and non-reversing component of the heat flow response [16; 17]. Thermogravimetric analysis (TGA) measures the changes in the sample's mass as a function of temperature. The loss of mass during the analysis provides an understanding of the chemical composition of the material. It can be caused by many processes and gives information about occurring phenomena, e.g., phase transition, desorption absorption, thermal decomposition, reduction or oxidation. TGA can be used to evaluate the thermal stability of the sample. In thermally stable samples, no changes in mass are observed over time [18].  
Due to this, the use of thermal analysis such as thermogravimetry or differential scanning calorimetry could be considered as a useful tool to determine the final quality of coffee beans during the roasting process but also to characterize the thermal parameters of the fat extracted from coffee beans [13].  
Taking the aforementioned reasons into account, the objective of this study was to evaluate the thermal properties of coffee powders obtained from Brazilian coffee beans of different roasting degrees, which were characterized using thermogravimetry analysis at nitrogen and oxygen flow and using modulated differential scanning calorimetry (MDSC). The thermal behaviour of the fat obtained from these beans was also studied.