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Fatty acid profiles in coffee (green and roasted) and its wasted fractions (spent coffee ground and silver skin)

The re-utilisation of spent coffee ground (SCG) and coffee silver skin (CSS) has gained a large interest due to increasing of awareness for waste reduction and environmental protection, and to opening the possibilities for isolation of various value-added compounds. The concept of re-utilization of these low-cost biomasses was undertaken in this study with the aim to evaluate the recovery of fatty acids (FAs). For comparison purposes the FAs are identified and quantified in green and roasted coffees from which these residues are generated. After trans-esterification of fatty acids extracts obtained after Soxhlet treatment of coffees and its by-products the analyses were done using GC-FID analysis. The results showed that palmitic acid (C16:0) with contents of 34.1 and 40.32 % is the most abundant saturated fatty acids (SFA) in roasted and green coffees, followed by stearic (C18:0) with the mass fraction of 7.39 and 9.36 %, respectively. Among monounsaturated fatty acids (MUFA), the roasted and green coffees contained the oleic (C18:1-9c) with mass fractions of 11.53 and 12.71 %, respectively. Regarding the polyunsaturated fatty acids (PUFA), the major one is linoleic (C18:2-6, cis) with contents of 41.38 % (roasted coffee) and 25.31 % (green coffee). The results also revealed that SCG contains the similar quantities of palmitic (34.36 %), stearic (7.65 %) and oleic (10.15 %) as roasted coffee, which points out that processing of roasted coffee to obtain brew did not influence on degradation of these FAs. In comparison with coffees and SCG, in the CSS dominates behenic (C22:0) with quantity of 21.03 %, followed by palmitic (18.75 %), aracchidic (18.40 %), stearic (5.1 %) and lignoceric (C24:0) in quantity of 5.12 %. The CSS in comparison with other analysed samples contained the minor amount of oleic (7.15 %) as MUFA. Although the linoleic is major PUFA in SCC, its content is lower than that found in roasted coffee. Overall, the results showed that total mass fractions of saturated and un-saturated FAs in evaluated samples are 70.72 and 24.26 % for CSS, 55.05 and 39.64 % for green coffee, 45.68 53.43 % for roasted coffee and 45.88 and 53.46 % for SCG, respectively. Thus, considering the obtained values it could be concluded that not only coffees, but also the residues generated from them are useful, beneficial sources of FAs.

coffee ; coffee by-products ; fatty acids ; GC-FID

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