Antioxidant Activity of Spent Coffee Ground Extracts towards Soybean Oil and Fish Oil

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 °C, 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.

Practical application: Due to lack of information about the antioxidant activity of spent coffee ground (SCG) extracts, this study was specifically aimed and designed to provide information on their activity towards soybean oil and fish oil during actual storage. This study showed that 0.25% acetone extract had equal or better protective effects than butylated hydroxytoluene (BHT) in soybean oil at 35 and 50 °C. The activity was further improved with increasing concentration. The activity of the acetone extract in fish oil was not as strong as in soybean oil, but higher concentrations further improved the antioxidant activity. In this study, it was clearly demonstrated that the SCG extracts could have practical use as natural antioxidants for vegetable oils and oils with high concentration of omega‐3 fatty acids.

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