Abstract
The aim of the present study was to establish the influence of high-temperature heating on the composition and thermal behavior of coffee oils obtained from Arabica green and roasted coffee beans, respectively. Morphological studies performed using scanning electron microscopy revealed the oil bodies uniformly distributed within the cells in both types of coffee beans analyzed. The obtained oils have a fatty acid composition rich in linoleic acid, palmitic acid, oleic acid, stearic acid, arachidic acid and linolenic acid. The total content of saturated fatty acids of investigated oils was 49.38 and 46.55%, the others being unsaturated fatty acids. The thermal behavior and thermo-oxidative stability of coffee oils extracted from green coffee beans and roasted coffee beans, the coffee oil high-temperature heated up to 200 °C, were investigated using simultaneous thermal analysis TG/DTG/DTA, in an oxidizing atmosphere. The data obtained for the analyzed samples depend mainly on the nature and compositions of fatty acids, and to a lesser extent on the roasting process of the coffee beans and the high-temperature heating process of the extracted oil. The chromatographic and TG/DTG/DTA data suggest that Arabica coffee oil has great potential for use in technological processes which require high-temperature heating (e.g. food industry or pastries).
Highlights
The lipid content of the coffee is mainly determined by the coffee species: Coffea arabica (Arabica), Coffea canephora (Robusta), and Coffea liberica
The literature currently available contains little, about the effect on the thermo-oxidative stability and fatty acid composition of the oil extracted from roasted and green coffee beans, of exposure of that oil to high temperatures. This was our main motivation for carrying out this study, which aims to assess the behavior of the lipid fraction of green and roasted Arabica coffee oils (GCO and roasted coffee oil (RCO)) when they are subjected to high-temperature heating (HGCO and heated roasted coffee oil (HRCO)), similar to pastry processing. In response to this lack of available information, our study addresses the following questions: (1) Does the roasting process of Arabica coffee beans, and high-temperature heating up to 200 ̊C of the extracted oils, induce changes in the composition of fatty acids? (2) How does the roasting process of Arabica coffee beans, and high-temperature heating up to 200 ̊C of the Characterization of crude and heated extracted oil from Arabica coffee beans extracted oils, influence the thermal behavior and thermo-oxidative stability of the samples? (3) What is the morphological difference between the green and roasted coffee beans used for obtaining the coffee oils?
In the present study we showed that the morphology of roasted coffee beans is preserved in comparison with that of green coffee beans, and that the oil bodies are uniformly distributed within the cells
Summary
The lipid content of the coffee is mainly determined by the coffee species: Coffea arabica (Arabica), Coffea canephora (Robusta), and Coffea liberica. The most popular varieties of coffee from which oil is extracted are Arabica (the average oil content is 15% on a dry basis) and Robusta (containing about 10% oil) [1,2,3,4,5]. A small quantity is located in the outer layer of the grain, and contains wax, oil and unsaponifiable matter, which have the role of preventing flavour volatilization during the roasting process [1, 18]. The saponifiable lipids fraction of green coffee beans contains triacylglycerols (about 75%), phospholipids and kaurane esterified diterpenes [18, 27]. The unsaponifiable fraction consists in sterols, tocopherols, free diterpenes, waxes and small amounts of other compounds with antioxidant properties, antimicrobial and antiproliferative activity [1, 28]
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