DETERMINATION OF CHLOROGENIC ACIDS WITH LACTONES IN ROASTED COFFEE

An HPLC method has been developed which allowed the determination of m ono- and dicaffeoylquinic acids (CQA and di-CQA), corresponding lacton es (CQL) and feruloylquinic acids (FQA) in roasted coffee within one c hromatographic run. The elution order was verified by isolation of the individual compounds by preparative HPLC, chromatography of the fract ions on the analytical HPLC system, NMR spectroscopy and thermospray L C-MS. At least 15 additional minor compounds had the spectra of hydrox ycinnamic acids, some of them only occurring in roasted coffee. Caffeo yltryptophan, which has been identified some time ago by another worki ng group could also be separated with this system. The average content s in commercial roasted coffee samples (n = 12) were: 3-CQA, 5.0 g kg( -1); 4-CQA, 6.2 g kg(-1); 5-CQA, 11.4 g kg(-1); 4-FQA, 0.7 g kg(-1); 5 -FQA, 1.4 g kg(-1); 3-CQL, 2.1 g kg(-1); 4-CQL, 1.0 g kg(-1); 3,4-di-C QA, 0.7 g kg(-1); 3,5-di-CQA, 0.4 g kg(-1) and 4,5-di-CQA, 0.8 g kg(-1 ) dry matter. There were only small differences between the different brands. Two series of samples with different degrees of roast produced from the same green coffee have also been analysed. One series was st eam treated before roasting (a process which is commercially used to i mprove digestibility). Only in the initial stages of roasting (light r oast) could a difference in the contents of the acids between both ser ies be observed. Keeping coffee brews at an elevated temperature (4 h at 80 degrees C) reduced the amounts of CQL to 60% of the initial valu e. The contents of 3-CQA and 4-CQA increased, whilst that of 5-CQA dec reased. The overall contents of CQA decreased.