Evaluation of Antioxidant and Antimicrobial Activities in Spent Coffee Grounds

Lian, Yong Liang (2020) Evaluation of Antioxidant and Antimicrobial Activities in Spent Coffee Grounds. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

The high demand for coffee beverages has caused significant amounts of coffee by-products, such as spent coffee ground (SCG), the by-product obtained after the coffee brewing process. SCG from Arabica, Robusta and Liberica, were extracted and analysed for their quantity of bioactive compounds (caffeine, chlorogenic acid and melanoidins). The SCG extracts were also evaluated for antioxidant (DPPH, FRAP, ABTS and Folin-Ciocalteu assays) and antimicrobial activities. The relationship of the bioactive compounds and the antioxidant activities of the SCG has been evaluated too. The caffeine content ranged from 10.71 – 15.91 mg/g and chlorogenic acid (CGA) ranged from 9.06 – 11.57 mg/g. Melanoidins content ranged from 388.48 – 496.97 mg/g, which represents the highest amount of bioactive compounds in SCG. Arabica SCG extract found to exhibit the highest antioxidant activities, followed by Robusta and Liberica. All SCG extracts possessed the potential of antioxidant properties which was due to the consequences of the presence by their concentrations of caffeine, phenolic compounds and melanoidins. Caffeine and melanoidins are the compounds that highly correlated to the antioxidant activities in SCG. The antimicrobial activity in SCG extracts was observed and Gram-positive bacteria (Staphylococcus aureus) was more susceptible than Gram-negative bacteria. The minimal inhibitory concentration (MIC) of SCG extracts for Gram-positive bacteria (8 mg/mL) was lower than Gram-negative bacteria (32-64 mg/mL). The mechanisms of the bioactive compounds in antioxidant and antimicrobial activities of SCG was discussed.