How to get antioxidants from coffee residue

A team of researchers from the University of Cordoba have obtained substances that enhance the antioxidant benefits of food and pharmaceutical products from the remainders of the coffee industry. In a process where they apply so-called 'green' solvents, experts are developing a faster and more efficient method for extracting these components.

The research group aims to give value to the coffee residue by recovering these healthy substances and minimizing the generation of waste. The extracts obtained from coffee residue showed high antioxidant capacity and antimicrobial effects that would be suitable to use as supplements in food and cosmetics. A solvent called supramolecular, can obtain extracts rich in value-added compounds at a very low cost and quickly.

Supramolecular solvents (SUPRESSIONS) are liquids with a tiny internal structure, made up of aggregates the size of microns or nanometres, a diameter a thousand times smaller than the thickness of a hair. Their synthesis is very simple and inexpensive, they have low toxicity and are sustainable, as they can be obtained from renewable sources. Ingredients that are widely used in food and cosmetics are employed to facilitate their use in these industries.

The term supramolecular was coined by this particular research team and is now used by the entire scientific community. "They are also known as 'green' or 'smart' solvents because they have the ability to change in the presence of an external stimulus, such as temperature or the addition of salts, and return to their natural state once they have recovered their initial characteristics. This allows them to be very functional and versatile," says Ana Ballesteros, co-author of the article.

In addition, the extracts obtained from coffee residues showed a high antioxidant capacity and antimicrobial effects suitable for use as supplements in food and cosmetics. "Extraction with SUPRAS offers fast, simple and low-cost methods and has a high potential to be applied directly to the extraction of bioactives from by-products of the food industry, such as coffee," adds the researcher.

Coffee to wake up the industry

Through the extraction of these solvents, an economic and simple method is achieved with which the bioactive compounds are separated and prepared for use. At the same time, value is given to the coffee waste by not requiring a large investment to obtain the beneficial substances they produce, which would enhance the activity of coffee-producing areas in developing countries like Colombia.

It is proposed to use supramolecular hexanol solvent, an alcohol used in perfumes and as a flavouring in food, to begin commercial validation tests.

The technique used involves a rapid one-minute phase of stirring the coffee wells with the SUPRAS and subsequent separation by centrifugation at room temperature of the product. The 'smart' solvent is then separated from the insoluble remains of the sample. In order to recover as many bioactive substances as possible from the coffee residue, different ingredients were studied to form the solvents. 

After the identification and characterization of the extracts obtained, the experts concluded that caffeine and chlorogenic acids are the two main representatives of alkaloids and polyphenols, respectively, among another great variety of bioactives with a high antioxidant capacity and that are present in these residues.

Among the different supramolecular solvents used, the researchers propose the use of SUPRAS of hexanol, an alcohol used in perfumes and as a flavouring in food, as the ideal one to start commercial tests to validate this clean and cost-effective method for direct application in the coffee industry.

The study has been financed through the Ministry of Science and Innovation's project "Functional supramolecular bio-solvents for the development of sustainable extraction technologies in the agri-food sector".