Oligosaccharides are indigestible carbohydrates widely present in mammalian milk and in some plants. Milk oligosaccharides are associated with positive health outcomes; however, oligosaccharides in coffee have not been extensively studied. We investigated the oligosaccharides and their monomeric composition in dark roasted coffee beans, brewed coffee, and spent coffee grounds. Oligosaccharides with a degree of polymerization ranging from 3 to 15, and their constituent monosaccharides, were characterized and quantified. The oligosaccharides identified were mainly hexoses (potentially galacto-oligosaccharides and manno-oligosaccharides) containing a heterogeneous mixture of glucose, arabinose, xylose, and rhamnose. The diversity of oligosaccharides composition found in these coffee samples suggests that they could have selective prebiotic activity toward specific bacterial strains able to deconstruct the glycosidic bonds and utilize them as a carbon source.

In this study, we developed and validated a new analytical method for the quantitative evaluation of uric acid in delactosed permeate using ion chromatography coupled with an ultraviolet detector. Uric acid was extracted from delactosed permeate samples by diluted hydroxide solution at room temperature. The separation was carried out on a high‐capacity anion‐exchange column by isocratic elution with 50 mM potassium hydroxide. Uric acid was detected at 295 nm. The results from this study demonstrate that the new ion chromatography‐ultraviolet method facilitates both the resolution and the detection of uric acid and provides a highly accurate and sensitive determination of uric acid in delactosed permeate samples with minimal sample preparation effort. The new method provided an excellent range of analyte response linearity in the 2.5–255.6 ng range with R2 > 0.99. The limit of detection for uric acid obtained was 0.04 mg/kg in 1 mM sodium hydroxide. Intraday and interday variabilities were less than 3%, and the mean recoveries (%) of the uric acid spiked in two types of delactosed permeate were between 100.4% and 103.9%. This method was successfully applied to determine uric acid amounts in ten delactosed permeate samples.

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Emerging research into the bioactivities of indigestible carbohydrates is illuminating the potential of various foods and food streams to serve as novel sources of health-promoting compounds. Oligosaccharides (OS) are widely present in milks and some plants. Our previous research demonstrated the presence of OS in brewed coffee and spent coffee grounds. Armed with this new knowledge, the next step toward improving the utilization of these valuable components involved investigating the effect of roasting on the formation and abundance of coffee OS. In the present study, we used advanced mass spectrometry to analyze a variety of coffee samples and demonstrated that a great structural diversity and increased abundance of OS is associated with higher roasting intensity. The present investigation also evaluated methods for OS extraction and fractionation. A preparative-scale chromatographic method, based on activated carbon, was developed to isolate enough amounts of OS from coffee to enable future confirmation of prebiotic and other in vitro activities.

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