Investigations of peptides and proteases in green coffee beans

The isolation and cleaning of peptides from green coffee beans are describe d. The peptide contents, the two-dimensional electrophoresis pattern and th e overall amino acid composition were determined using five samples of Coff ea arabica and four samples of Cof. canephora var. robusta. The coffee type s were not significantly different in peptide content, but were significant ly different in peptide composition. Peptides with weakly acid pI values we re mainly found in the Cof. robusta samples. In comparison, peptides from C of. arabica samples ranged evenly from the weakly acidic up to the weakly b asic pH range. The apparent molecular masses of the peptides in the two gro ups of samples lie between 4 kDa and 10 kDa. The cysteine content of the pe ptides was relatively high. Model roastings permitted the assumption that p eptides make a contribution to coffee flavour. Peptides are already availab le in freshly harvested coffee. Model tests have suggested that processing after the coffee harvest has an influence on peptide composition but not on the amounts of peptide. All coffee samples contained some extractable prot eases. The electrophoretically obtained enzyme patterns of Cof. arabica and Cof. robusta were different.