Microwave-Assisted Extraction of Phenolic Compounds from Spent Coffee Grounds. Process Optimization Applying Design of Experiments

Abstract

In this study, sustainable technology microwave-assisted extraction (MAE) in association with green solvents was applied to recover phenolic compounds from spent coffee grounds (SCGs). A design of experiments (DOE) was used for process optimization. Initially, a 24−1 two level Fractional Factorial Design was used and ratios “solvent to solute” and “ethanol to water” were identified as the significant experimental factors. Consequently, Central Composite Design (CCD) was applied to analyze the effects of the significant variables on the response yield, total polyphenols content (TPC), and antioxidant activity (AA) by the DPPH assay method, and quadratic surfaces to optimize those responses were generated. The values of the significant factors of 16.7 (solvent/solute) and 68.9% (ethanol/water) were optimized simultaneously the yield (%) at 6.98 ± 0.27, TPC (mg GAE/g) at 117.7 ± 6.1, and AA (µmol TE/g) at 143.8 ± 8.6 and were in excellent agreement with those predicted from the CCD model. The variations of the compositions of the lipids, caffeine, pentacyclic diterpenes, and FAME as a function of the dominant factor % ethanol in the solvent mixture were analyzed by applying NMR and GC-FID, and the results obtained confirmed their determinative significance.

Optimization of 5-CQA Extraction Conditions from Green Coffee By-Product (Coffea arabica) Using a Response-Surface Design and the Study of Its Extraction Kinetics

“…Adequacy accuracy is a signal-to-noise ratio. It compares the range of predicted values at the design points to the mean prediction error, and a value greater than 4 is adequate [ 29 , 32 ], which was verified in our case (15.5083). Thus, the regression equation could be applied for the prediction of the optimal conditions of the extraction process.…”

Investigation of the Genotoxic, Antigenotoxic and Antioxidant Profile of Different Extracts from Equisetum arvense L.

“…Plant extracts are widely used for the production of novel therapeutic drugs against a number of ailments [ 1 , 2 ]. Solvents, such as ethanol, methanol and water, are extensively used for the extraction of valuable compounds of different origin [ 10 , 35 , 36 , 37 , 38 ]. The results of the present study show that these solvents were very effective and could mediate the beneficial effects of the plant E. arvense L., at least in the case of its cytogenotoxic potential.…”

The Potential of Spent Coffee Grounds in Functional Food Development

“…The recovery of these compounds from SCG has used a range of methods of extraction [ 69 , 70 ]. Some of these methods include conventional solvent extraction, high hydrostatic pressure-assisted extraction, ultrasound-assisted extraction and microwave-assisted extraction [ 69 , 70 , 71 , 72 ]. Further, extraction methods have also been studied for coffee oil, which is a rich source of fatty acids and caffeine [ 73 , 74 ].…”