Optimal Aqueous Extraction Conditions as A Green Technique for Recovery of Phenolic Antioxidants from Robusta Dried Coffee Pulp

Abstract

Coffee pulp, a by-product of coffee processing, contains high level of flavonoids and other phenolic compounds. This by-product also contains high levels of other bioactive compounds such as chlorogenic acids and caffeine, which can be potentially recovered for further applications. This study used water as an inexpensive green solvent, for the maximum recovery of phenolics, major bioactive compounds and antioxidant capacity from coffee pulp. Recovery yield from optimal aqueous extraction was compared with organic solvent extraction. The results showed that temperature, extraction time and solid/solvent ratio significantly affected recovery yields from coffee pulp (P<0.05). Optimal aqueous extraction conditions were 100 °C, 60 min and the ratio of sample to solvent 1:100 g/mL. Under these optimal conditions, recovery yields were similar to those of 50% aqueous acetone extraction. Recovery yields were significantly higher than pure acetone, methanol and ethanol as well as methanol and ethanol in combination with water (50% v/v). Therefore, these optimal aqueous conditions are recommended for recovery of bioactive compounds from coffee pulp for further applications.

Recovery of Phenolic Compounds and Antioxidants from Coffee Pulp (Coffea canephora) Waste Using Ultrasound and Microwave-Assisted Extraction

“…Coffee pulp, also known as the mesocarp of coffee beans, is the main residue produced during coffee production, and constitutes up to 40% by weight of coffee cherries. However, Processes 2022, 10, 1011 2 of 10 the coffee pulp by-product has not been utilized effectively [7], and is typically dumped in landfills, which causes a significant environmental pollution and toxic effects for people living nearby the waste effluent [8,9]. This by-product is rich in nutritive compounds, such as protein and carbohydrates, and phytochemicals, such as phenolic compounds, tannins, and caffeine [10].…”

“…Extraction methods can be categorized as conventional or advanced techniques. Conventional methods, for example solvent and steam extraction, are simple to set up, but they are often high cost due to labor, time, solvent consumption, loss of targeted compounds, and low extraction yields [7]. In contrast, advanced techniques, such as microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE), require more sophisticated equipment, but can overcome these barriers [15].…”

Antioxidation and Tyrosinase Inhibitory Ability of Coffee Pulp Extract by Ethanol

“…Currently, the common extraction method for extracting coffee pulp is solvent extraction. Methanol is used as the main solvent [24][25][26][27][28], whereas ethyl acetate [26], isopropanol [13], acetone [25,27], and hydrochloric acid [29] are used for extraction analysis. However, these solvents are unsafe for the human body.…”

Valorization of coffee bean husk via pressurized liquid extraction for production of physicochemical extract

“…Tahirović et al 59 verified a reduction of 15.5% in the TPA content in the extract of fruits of Prunus spinosa L. with the increase of ethanol in the solvent from 50% to 80%. Similarly, Zhu et al 60 and Tran et al 56 verified a reduction in TPA, TPC, and TFC contents when changing the solvent from hydroethanolic (50% v/v of ethanol) to absolute ethanol.…”

“…In larger proportions, this variable acts by increasing the contact area between solvent and matrix, so that solutes will be more likely to move into the solvent, increasing extraction rates. Tran et al 56 reinforced this information by obtaining twice the TPC and TFC contents in the aqueous extraction of robusta dried coffee pulp when increasing the proportion (solvent to sample) from 10 to 40 mL g −1 .…”