Incorporation of chlorogenic acids in coffee brew melanoidins.
The incorporation of chlorogenic acids (CGAs) and their subunits quinic and caffeic acids (QA and CA) in coffee brew melanoidins was studied. Fractions with different molecular weights, ionic charges, and ethanol solubilities were isolated from coffee brew. Fractions were saponified, and the released QA and CA were quantified. For all melanoidin fractions, it was found that more QA than CA was released. QA levels correlated with melanoidin levels, indicating that QA is incorporated in melanoidins. The QA level was correlated with increasing ionic charge of the melanoidin populations, suggesting that QA may contribute to the negative charge and consequently is, most likely, not linked via its carboxyl group. The QA level correlated with the phenolic acid group level, as determined by Folin-Ciocalteu, indicating that QA was incorporated to a similar extent as the polyphenolic moiety from CGA. The QA and CA released from brew fractions by enzymes confirmed the incorporation of intact CGAs. Intact CGAs are proposed to be incorporated in melanoidins upon roasting via CA through mainly nonester linkages. This complex can be written as Mel=CA-QA, in which Mel represents the melanoidin backbone, =CA represents CA nonester-linked to the melanoidin backbone, and -QA represents QA ester-linked to CA. Additionally, a total of 12% of QA was identified in coffee brew, whereas only 6% was reported in the literature so far. The relevance of the additional QA on coffee brew stability is discussed.
Bekedam
E Koen
EK
Laboratory of Food Chemistry and Product Design and Quality Management Group, Department of Agrotechnology and Food Science, Wageningen University, Wageningen, The Netherlands.
Schols
Henk A
HA
Van Boekel
Martinus A J S
MA
Smit
Gerrit
G
D002109:Caffeic Acids / Q000032:analysis / Q000737:chemistry; D002726:Chlorogenic Acid / Q000737:chemistry*; D002852:Chromatography, Ion Exchange; D040503:Coffea / Q000737:chemistry; D003069:Coffee / Q000737:chemistry*; D003373:Coumaric Acids / Q000032:analysis; D006358:Hot Temperature; D008970:Molecular Weight; D011108:Polymers / Q000032:analysis / Q000737:chemistry*; D011801:Quinic Acid / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D012639:Seeds / Q000737:chemistry
D002109:Caffeic Acids; D003069:Coffee; D003373:Coumaric Acids; D011108:Polymers; C472707:caffeoylquinic acid; C011908:melanoidin polymers; D011801:Quinic Acid; D002726:Chlorogenic Acid; C004999:ferulic acid; C040048:caffeic acid