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A study on the protein fraction of coffee silverskin: Protein/non-protein nitrogen and free and total amino acid profiles.

Food chemistry (2020-05-16)
Susana Machado, Anabela S G Costa, Filipa Pimentel B, M Beatriz P P Oliveira, Rita C Alves
ABSTRACT

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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
L-Glutamine, BioUltra, ≥99.5% (NT)
Sigma-Aldrich
L-Aspartic acid, BioUltra, ≥99.5% (T)