A study on the protein fraction of coffee silverskin: Protein/non-protein nitrogen and free and total amino acid profiles
2020
Machado, Susana | Costa, Anabela S.G. | Pimentel B., Filipa | Oliveira, M. Beatriz P.P. | Alves, Rita C.
Silverskin, the main coffee roasting by-product, is rich in fiber, protein and antioxidants. Its protein fraction was studied regarding total, protein and non-protein nitrogen content. Amino acids were analysed after automated on-line derivatization. The method showed to be precise (<6.9%) and accurate (recoveries using a certified reference material and spiked blanks: 90–102%; for spiked samples: 73–113%). The real protein content of silverskin was 12%. One quarter of the total nitrogen corresponded to the non-protein fraction. All essential amino acids were present in the free form, except methionine. Regarding total amino acids, aspartic and glutamic acids (9–10 mg/g) were the major compounds. Branched chain amino acids (leucine, isoleucine and valine) were also present in substantial amounts (5–8 mg/g), as well as proline and arginine (~5 mg/g). Concluding, silverskin is a source of amino acids with relevance for the improvement of cognitive and physical performances.
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