Optimization of the Extraction from Spent Coffee Grounds Using the Desirability Approach

Area of Science:

• Food Science & Technology
• Biotechnology
• Analytical Chemistry

Background:

• Spent coffee grounds (SCG) are a rich source of bioactive compounds.
• Valorization of SCG is crucial for sustainable waste management and resource recovery.
• Previous studies highlight SCG's potential but lack optimized extraction protocols for specific compounds.

Purpose of the Study:

• To optimize the extraction of valuable compounds (caffeine, trigonelline, nicotinic acid) from 100% Arabica spent coffee grounds.
• To determine the ideal extraction conditions (temperature, solvent volume) using a desirability approach and Response Surface Methodology (RSM).
• To evaluate the physicochemical properties, elemental composition, and in vitro biological activity of the optimized spent coffee extract.

Main Methods:

• Extraction optimization using Response Surface Methodology (RSM) with a Central Composite Design (CCD).
• Analysis of caffeine, trigonelline, and nicotinic acid using High-Performance Liquid Chromatography with a Visible-Ultraviolet Detector (HPLC-VWD).
• Assessment of total phenol content (TPC) via Folin-Ciocalteu assay and antioxidant capacities (AC) using DPPH, FRAP, and ABTS assays.
• Elemental analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and in vitro cytotoxicity and antioxidant assays on HaCaT cells.

Main Results:

• Optimal extraction conditions identified as 80°C and 20 mL of water per gram of SCG, maximizing caffeine, trigonelline, and nicotinic acid recovery.
• The optimized extract exhibited high total phenol content and significant antioxidant capacities (DPPH, FRAP, ABTS).
• ICP-MS revealed potassium as the most abundant element, with negligible heavy metal content. In vitro studies showed dose-dependent cytotoxicity and significant reduction of intracellular reactive oxygen species in HaCaT cells.

Conclusions:

• The study successfully optimized the extraction of bioactive compounds from spent coffee grounds, demonstrating its potential as a valuable resource.
• The optimized extract possesses significant antioxidant properties and a favorable elemental profile, suggesting applications in nutraceuticals or cosmetics.
• Spent coffee extract shows promise for reducing oxidative stress in cells, with safety considerations regarding concentration.