Abstract
The aim of the study was to characterize the thermal properties of coffee silverskin and fat extracted from the material by using differential scanning calorimetry, modulated differential scanning calorimetry and thermogravimetry/derivative thermogravimetry. Additionally, the thermokinetic parameters, oxidative stability and fatty acid composition of the extracted oil were defined. Thermal decomposition of the studied coffee roasting by-product under oxygen occurred in three defined stages. The most significant changes in weight were observed in the region of 200–500 °C and correspond to polysaccharide decomposition. These results are in agreement with the data obtained from the differential scanning calorimetry curve. On the curve course of silverskin, two main exothermic peaks can be observed with a maximum at 265 and 340 °C. These exothermic events represent the transitions of hemicellulose and cellulose. Fat extracted from silverskin turned out to be a source of polyunsaturated fatty acids with the recommended n-6 to n-3 ratio reaching the value 4:1. The studied fat was characterized by low oxidative stability. Considering the obtained results, it can be stated that thermal analysis can provide fast and reliable data concerning the composition and properties of coffee silverskin and coffee silverskin oil.
Highlights
Coffee is one of the most consumed beverages in the world and is produced in great amounts [1].Among the many steps in coffee production, the roasting process seems to be of great importance, as under the influence of high temperature, many physicochemical changes occur
The obtained results contributed to better characterization of coffee silverskin as a valuable by-product of the coffee roasting process
Profile indicates the occurrence of two main exothermic peaks, which represent the main components of silverskin, hemicellulose and cellulose
Summary
Coffee is one of the most consumed beverages in the world and is produced in great amounts [1]. Among the many steps in coffee production, the roasting process seems to be of great importance, as under the influence of high temperature, many physicochemical changes occur. Sci. 2020, 10, 8790 process, an outer layer of green coffee beans, known as coffee silverskin, is removed [2]. Green coffee beans with attached tegument (silverskin) are exported to consuming countries, where the coffee beans undergo the roasting process [3]. The amount of this waste depends on the type of green beans and on the conditions of processing used, but mostly, coffee silverskin represents about
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