Spent Coffee Grounds’ Valorization towards the Recovery of Caffeine and Chlorogenic Acid: A Response Surface Methodology Approach

Abstract

The amount of spent coffee grounds (SCGs) created, represents an environmental challenge worldwide. In this context, the aim of the present study was to exploit the potential of SCGs as a source of bioactive compounds that can be utilized in high value-added products. Thus, a cost-effective and environmentally friendly extraction technique was developed to ensure extracts with high total phenolic content and antioxidant activity, as well as significant amounts of caffeine and chlorogenic acid. Response surface methodology was implemented to evaluate the effects of the main extraction parameters (i.e., time, temperature, and ethanol-to-water ratio) and their interactions on the defined responses. The ethanol ratio was found to be the most significant variable. Then, a set of optimum values was determined (i.e., 7 min, 75 °C, and ethanol:water ratio 5:95), where the predicted values for responses were found to be 5.65% for the yield (Y1), 152.68 mg gallic acid equivalents per L for total phenolic content (Y2), 0.797 μmol Trolox equivalent per mL for the antioxidant activity (Y3), 30.5 ppm for caffeine concentration (Y4), and 17.4 ppm for chlorogenic acid concentration (Y5). Furthermore, the corresponding high experimental values from the validation experiment fitted well to these predictions, clearly clarifying the high potential of SCG extracts for use in high value-added applications.

Spent Coffee Grounds Valorization as Bioactive Phenolic Source Acquired Antifungal, Anti-Mycotoxigenic, and Anti-Cytotoxic Activities

“…The global coffee production in 2020/2021 is about 10.17 million metric tons, which means about 6.5 million tons of SCGs have resulted from extraction [4]. The valorization of the SCGs through their implementation in biogas, food, feed, cosmetic, pharmaceutical, soil composites, and electricity production has been referred to before [5].…”

Bioactive Compounds and Antioxidant Activity from Spent Coffee Grounds as a Powerful Approach for Its Valorization

“…According to the International Coffee Organization, over 169 million 60 kg bags of coffee were produced in 2020, which represents a 0.3% increase from the previous year. With coffee production and consumption being expected to steadily grow in the next years, the amount of byproducts produced by the coffee industry is also projected to increase [ 1 , 2 ]. Several byproducts are generated during the processing that coffee undergoes until it reaches the final roasted beans, including the husk, pulp, mucilage, parchment, silver skin, and spent coffee grounds.…”

Spent Coffee Grounds Valorization in Biorefinery Context to Obtain Valuable Products Using Different Extraction Approaches and Solvents

“…Based on the data published by the International Coffee Organization, global coffee consumption reached 10 million tons in 2020/21 [ 3 ]. SCG ending up in landfills, emits 28.6 million tons of CO 2 eq annually, which is comparable to 10.6 million litres of burned diesel fuel [ 4 , 5 ]. Decomposing spent coffee grounds releases methane into the atmosphere; methane is the second most abundant greenhouse gas and has a global warming potential up to 43 times greater than CO 2 .…”