Extraction and Chemical Characterization of Functional Phenols and Proteins from Coffee (Coffea arabica) By-Products.

Barbara Prandi,Maura Ferri,Annalisa Tassoni,Ilaria Cigognini,Stefano Sforza,Dennis Schaller,Luciano Navarini,Tullia Tedeschi,Stefanie Verstringe,Stefania Monari,Chiara Zurlini,Martha Walter

doi:10.3390/biom11111571

Abstract

Not all the coffee produced goes to the roasting stage, because non-compliant green coffee beans are usually discarded by roasters and the silverskin of the coffee is usually removed and discarded. In the present work, non-compliant green coffee beans and coffee silverskins were fully characterized from a chemical point of view. In addition, enzyme-assisted extraction was applied to recover a fraction rich in proteins and polyphenols, tested for antimicrobial, antityrosinase, and antioxidant activities. Non-compliant green coffee beans showed higher amounts of polyphenols, flavanols, flavonoids, and caffeine than coffee silverskins (which were richer in tannins). The enzymatic extraction of non-compliant coffee green beans produced extracts with a good protein content and with a consistent quantity of polyphenols. The extract showed antioxidant, antityrosinase, and antimicrobial activity, thus representing a promising strategy to recover defective green coffee beans. The antioxidant and antimicrobial activity of coffee silver skins is lower than that of non-compliant coffee green beans extracts, while the antityrosinase activity is comparable.

Highlights

Global coffee production reached 170.94 million 60-kg bags in 2019, primarily produced in South America, and in Brazil (61.7 million 60-kg bags), followed by Vietnam and Colombia
All samples belonged to the Coffea arabica species
coffee green beans (CGBs) are discarded by roasters because they do not comply with the required quality standards

Summary

Introduction

Global coffee production reached 170.94 million 60-kg bags in 2019, primarily produced in South America, and in Brazil (61.7 million 60-kg bags), followed by Vietnam and Colombia. Roasters select coffee green beans (CGBs) to eliminate those that do not meet the required quality standards (non-compliant). The quantity of CGBs discarded depends on the selection criteria of the suppliers and the quality standards applied. These defective beans make up about 20% of total coffee production in Brazil and are separated from non-defective beans before being marketed [3]. The green beans are processed, using a dry or wet method. Two types of wastes are produced during wet processing: Biomolecules 2021, 11, 1571.

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