resumo
Three mixtures containing different molar proportions of (beta 1-4)-D-mannotriose and (alpha 1 -> 5)-L-arabinotriose, oligosaccharides structurally related to coffee polysaccharides (galactomannans and arabinogalactans), were roasted at 200 degrees C for different periods. Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MSn) analyses of labeled (180) and unlabeled samples allowed identification of not only nonhybrid oligosaccharides but also hybrid oligosaccharides composed of both hexose and pentose units. The identification of hybrid oligosaccharides allowed us to infer the occurrence of nonenzymatic transglycosylation reactions involving both oligosaccharides in the starting mixtures. Also, it was observed that using different proportions of the oligosaccharides in the starting mixtures and extents of thermal treatment led to a variation in the composition of the compounds formed. These results have led to the conclusion that, depending on the distribution of the polysaccharides in the bean cell walls and the roasting conditions, different nonhybrid and hybrid structures can be formed during coffee roasting.
palavras-chave
TANDEM MASS-SPECTROMETRY; STRUCTURAL FEATURES; GROUND POLYSACCHARIDES; ARABICA BEANS; SIDE-CHAINS; ARABINOGALACTANS; GALACTOMANNANS; GREEN; OLIGOSACCHARIDES; ARABINOTRIOSE
categoria
Agriculture; Chemistry; Food Science & Technology
autores
Moreira, ASP; Simoes, J; Nunes, FM; Evtuguin, DV; Domingues, P; Coimbra, MA; Domingues, MRM
nossos autores
Dmitry Evtyugin
Professor Associado com Agregaçãoagradecimentos
We thank Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), European Union, QREN, FEDER, and COMPETE for funding the QOPNA research unit (Project PEst-C/QUI/UI0062/2013; FCOMP-01-0124-FEDER-037296) and the Portuguese Mass Spectrometry Network (REDE/1504/REM/2005). Thanks are also due to FCT for the grants to A.S.P.M. (SFRH/BD/80553/2011) and J.S. (SFRH/BPD/90447/2012).