Antioxidant Activities of Different Varieties of Spent Coffee Ground (Scg) Extracted Using Ultrasonic-Ethanol Assisted Extraction Method

Abstract

Spent coffee grounds (SCG) a by-product from coffee industries, coffee shops and domestic users contain large amounts of organic compounds which could be re-used as source antioxidants for foods or cosmetics. This project aims to study the antioxidant activity of three different spent ground coffee varieties (Robusta, Liberica and Arabica) extracted using ultrasonic-ethanol assisted extraction method utilizing 60% ethanol. The extracted samples were analysed using DPPH, FRAP, FTC and TBA, total phenolic content, total flavonoid content and also individual flavonoids to measure the quality and quantity of antioxidative activity in spent coffee. Robusta and Liberica SCGs exhibited similar activity (p>0.05) towards DPPH scavenging and ferric reducing reaction. Both showed 77.99±0.92 and 77.75±0.04%, respectively for DPPH, and 26.82±2.92 and 24.41±0.49 mg TE/g dry sample, respectively for FRAP. In FTC and TBA analyses, Robusta SCG was found to have the least activity with 61.07±2.43% and 2.9±0.14% respectively. Spent Arabica has similar inhibition percentage (p>0.05) as Liberica SCG in FTC (57.08±0.9 and 50.54±4.23% respectively), yet has different inhibition activity (p<0.05) in TBA (4.3±0.14 and 7.4±1.41% respectively). Total phenolic and flavonoid contents were found to be the highest in Arabica SCG with 941.04±37.25 mg GAE and 78.21 mg QE/g dry sample, respectively. Liberica and Robusta SCGs contain a total of phenolic content of 661.14±2.86 and 547.51±59.5 mg GAE/g dry sample, respectively and a total of flavonoid content of 71.64±1.85 and 20.66±7.82 mg QE/g dry sample. Individual flavonoids of luteolin and quercetin were present in all the three spent ground coffee varieties. Results from the study illustrated that the three different varieties of SCGs showed different extract yields as well as diverse traits of antioxidant activity that could serve as a good antioxidant.

Physiochemical properties of Sarawak's adapted Liberica coffee silverskin utilizing varying solvents

“…Different standards used to calibrate will give different values of FRAP, such as shown in Benzie and Strain ( 1996 ) as they investigated different possible standards that be used in a standard compound for references and different standards showed different values of FRAP. This is also supported by the research completed by Ansori et al ( 2021 ), as there was 24.41 ± 0.49 mg TE/g of FRAP value estimated from Liberica coffee ground spent. In the current study, the results of the Liberica CS showed only as high as 11.40 ± 18.57 μmol FSE/g of FRAP value when compared to standard FeSO 4 instead of using Trolox.…”

Valorization of SCG through Extraction of Phenolic Compounds and Synthesis of New Biosorbent

“…All studies conducted on the extraction of phenolics from SCG using ultrasound-assisted extraction employed the aforementioned solvents and, more specifically, aqueous solutions of ethanol and methanol. As far as ethanol is concerned, under optimum extraction conditions, ethanol was found to be at concentrations of 50-60% (v/v) and extraction of phenolics after 4.5 h at 28 • C was achieved up to 941.04 ± 37.25 mg GAE/g dry sample [69]. On the other hand, the use of aqueous methanol resulted in lower extraction efficiencies, leading up to 24.95 mg GAE/g.…”

“…Similarly, in the case of extraction of phenolics from SCG using ultrasounds, it appears that the majority of researchers achieved satisfying extraction yields, ranging from 18.54 to 33.84 mg GAE/g SCG, under extractions for approximately 30 min (20-40 min). However, Ansori et al [69] achieved the highest recorded extraction efficiencies, extending the extraction time up to 4.5 h.…”