title: Microwave superheated water extraction of polysaccharides from spent coffee grounds.
abstract: The spent coffee grounds (SCG) are a food industry by-product that can be used as a rich source of polysaccharides. In the present work, the feasibility of microwave superheated water extraction of polysaccharides from SCG was studied. Different ratios of mass of SCG to water, from 1:30 to 1:5 (g:mL) were used for a total volume of 80 mL. Although the amount of material extracted/batch (MAE1) increased with the increase of the concentration of the sample, the amount of polysaccharides achieved a maximum of 0.57 g/batch for 1:10. Glycosidic-linkage composition showed that all extraction conditions allowed to obtain mainly arabinogalactans. When the unextracted insoluble material was re-extracted under the same conditions (MAE2), a further extraction of polysaccharides was observed (0.34 g/batch for 1:10), mainly galactomannans. Also, a high amount of oligosaccharides, mainly derived from galactomannans, can be obtained in MAE2 (0.96 g/batch for 1:10). This technology allows to obtain galactomannans and arabinogalactans in proportions that are dependent on the operating conditions.
authors.affiliation: QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal. cpassos@ua.pt
authors.forename: Cláudia P
authors.initials: CP
authors.lastname: Passos
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Coimbra
mesh_terms: D002236:Carbohydrate Conformation; D003069:Coffee / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D005590:Fractional Precipitation; D005685:Galactans / Q000737:chemistry / Q000302:isolation & purification; D005690:Galactose / Q000031:analogs & derivatives; D006358:Hot Temperature; D008351:Mannans / Q000737:chemistry / Q000302:isolation & purification; D008872:Microwaves; D011134:Polysaccharides / Q000737:chemistry / Q000302:isolation & purification*; D052616:Solid Phase Extraction / Q000379:methods; D012997:Solvents / Q000737:chemistry*; D014866:Waste Products; D014867:Water / Q000737:chemistry*
chemical_list: D003069:Coffee; D005685:Galactans; D008351:Mannans; D011134:Polysaccharides; D012997:Solvents; D014866:Waste Products; D014867:Water; C012990:galactomannan; D000431:Ethanol; C005653:arabinogalactan; D005690:Galactose