Antioxidant activity of spent coffee ground extracts toward soybean oil and fish oil

Authors: Hwang, Hong-Sik; Moser, Jill; KIM, YOUNGMOK - SYNERGY FLAVORS, INC.; Liu, Sean

Submitted to: European Journal of Lipid Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2019
Publication Date: 2/25/2019
Citation: Hwang, H.-S., Winkler-Moser, J.K., Kim, Y., Liu, S.X. 2019. Antioxidant activity of spent coffee ground extracts toward soybean oil and fish oil. European Journal of Lipid Science and Technology. https://doi.org/10.1002/ejlt/201800372.
DOI: https://doi.org/10.1002/ejlt/201800372

Interpretive Summary: This study showed that extracts from spent coffee ground (SCG), the waste generated during the coffee brewing process, can practically be used as natural antioxidants for vegetable oils and omega-3 oils. Coffee is one of the most popular and widely consumed beverages in the world. Due to such a large consumption, about nine million tons of SCG were thrown in land'lls in a year. It has been reported that SCG contains valuable bioactive materials and antioxidants. Especially, antioxidants in SCG are of great interest as valued-added products since the food industry is constantly looking for natural antioxidants for edible oils such as vegetable oils and omega-3 oils, which can replace synthetic antioxidants that have negative health effects. Previous studies, however, did not clearly show the effectiveness of SCG extracts compared to synthtic antioxidant in oil under actual storage conditions. In this study, we extracted SCG with acetone, ethanol, and hexane and tested these extracts in soybean oil as the representative of vegetable oils, and also in fish oil as a representative of omega-3 oils. We found that acetone extract had the strongest antioxidant activity among other extracts. The activity of 0.25% acetone extract was equal or better than butylated hydroxytoluene (BHT) at its legally limited concentration (0.02%) in soybean oil. For fish oil, 0.25% acetone extract was not as effective as 0.02% BHT, but the efficacy increased with increasing concentration making the activity closer to that of BHT. This study showed that SCG extracts can practically be used as natural antioxidants for vegetable oils and omega-3 oils.

Technical Abstract: Although studies have shown that spent coffee ground (SCG) extracts have antioxidant activity, no systematic study has been reported under actual storage conditions. The purpose of this study was to estimate the feasibility of practical application of SCG extracts as natural antioxidants for soybean oil and fish oil. An ethanol extract (EE), an acetone extract (AE), and polar compounds isolated from oil (PCO) were prepared and their activity was compared to a synthetic antioxidant, butylated hydroxytoluene (BHT). EE showed the strongest radical scavenging activity for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and the highest total phenolic content (TPC) followed by AE and then PCO. However, during storage of soybean oil and fish oil at 35 and 50 ºC, AE had the strongest antioxidant activity as determined by peroxide value, conjugated diene value, p-anisidine value, and headspace volatile analyses. In soybean oil, 0.25% AE had antioxidant activity that was equal to or better than 0.02% BHT. In fish oil, the antioxidant activity of 0.25% AE was inferior to that of 0.02% BHT. However, increased concentrations of AE showed improved antioxidant activity. This study showed that SCG extracts can be practically used as natural antioxidants for vegetable oils and omega-3 oils.