Quantitative and qualitative evaluation of fatty acid content in specialty coffee bean oil

Quantitative and qualitative evaluation of fatty acid content in specialty coffee bean oil
Yuri Koshima, M. Z. Islam, Mito Kokawa and Yutaka Kitamura
Graduate School of Life and Environmental Sciences, University of Tsukuba / ESALQ USP
[email protected]
Presentation: Poster
Summary
1. Introduction
Approximately 8 million ton of coffee is produced every year globally. Flavor characteristics of specialty coffee are highly appreciated in the market. Arabica species showed the higher oil percentages, which 10 to 17% of lipid content.[1][2] Coffee oil contains a good proportion of the aromatic constituents of medium and low volatility, and is little changed during roasting and protects the aroma compounds from degradation as roasting continues. Although they can be used as flavor for food products, they are mostly retained in the grounds during coffee beverage preparation, thus being discarded. [2] The present study showed the interest to evaluate composition of fatty acids and effective utilization of coffee oil.

2. Objectives
The aim of the study was to investigate the effect of roasting conditions on quality of specialty coffee oil and extraction characteristics. To determine the fatty acid composition of the coffee oil from roasted specialty coffee bean and consider effective use of coffee oil.

3. Methods
Specialty coffee bean samples (Arabica, from Kenya) roasted in 3 different level (light, medium and dark) were ground to 250-1050 μm. 20 g of coffee beans were extracted by 360 mL of hot water using metal filter. Then, each 20 g of ground beans and residue were eluded by 300 mL of hexane in Soxhlet method (1-8h) to extract oil. For solvent removal, the extract was concentrated in rotary evaporator.
The composition of fatty acid in samples were determined by GC/FID chromatographic method, using Nitrogen gas and packed column. ANOVA and Turkey’s test were performed for determination of significant differences of fatty acid contents.

4. Results and discussion
Roasting showed impact on the extraction rate of the coffee oil. The extraction rate from roasted beans increased from 9.8% to 15.9% from light to dark roast. The extraction rate from residue was 3.8%, still 30% of whole coffee oil on residue. The most effective condition was 6 h for extraction of the whole oil. Coffee oil is not water soluble, but 70% of the oil in the beans moved to the coffee liquid physically because during roasting pulverization and extraction, eluted and peeled off the surface of the beans. During hot water brewing, 30% of the oil did not rise to the surface, but stayed inside beans, being eluted by the organic solvent.
The GC/FID chromatographic analysis of the specialty coffee oil extract shows that the main fatty acids content in all samples were Myristic acid, Palmitic acid, Palmitoleic acid, Stearic acid, Oleic acid, Linoleic acid, Linolenic acid and Arachidic acid. Any significant difference in the fatty acid profile was observed due to the effect of roasting, but the total amount of fatty acids was greatly affected by hot water extraction. The fatty acid content decreased to one third before and after hot water brewing.

5. Conclusions
The concentration of coffee oil varied with roasting. Since the fatty acid compositions did not greatly change, it seems the properties of oil did not change significantly. This study concluded that the possibility of effective use of coffee oil extracted from specialty coffee bean in oily fragrance etc. For further utilization of coffee oil in residues, it is recommended that the oil extraction will be effective by selecting the appropriate extraction methods.

-References
[1] Budryn et al., Influence of roasting conditions on fatty acids and oxidative changes of Robusta coffee oil, 2012
[2] Speer & Kölling-Speer, The lipid fraction of the coffee bean,2006
[3] Oliveira, Cruz, Eberlin& Cabral, Brazilian roasted coffee oil obtained by mechanical expelling: compositional analysis by GC-MS,2005

Key words: Coffee oil, Fatty acids, GC/FID, Specialty coffee