title: Spectrophotometric total reducing sugars assay based on cupric reduction.
abstract: As the concentration of reducing sugars (RS) is controlled by European legislation for certain specific food and beverages, a simple and sensitive spectrophotometric method for the determination of RS in various food products is proposed. The method is based on the reduction of Cu(II) to Cu(I) with reducing sugars in alkaline medium in the presence of 2,9-dimethyl-1,10-phenanthroline (neocuproine: Nc), followed by the formation of a colored Cu(I)-Nc charge-transfer complex. All simple sugars tested had the linear regression equations with almost equal slope values. The proposed method was successfully applied to fresh apple juice, commercial fruit juices, milk, honey and onion juice. Interference effect of phenolic compounds in plant samples was eliminated by a solid phase extraction (SPE) clean-up process. The method was proven to have higher sensitivity and precision than the widely used dinitrosalicylic acid (DNS) colorimetric method.
authors.affiliation: Department of Chemistry, Faculty of Engineering, Istanbul University, 34320 Istanbul, Turkey. Electronic address: sozgen@istanbul.edu.tr.
authors.forename: Kevser Sözgen
authors.initials: KS
authors.lastname: Başkan
authors.affiliation: Department of Chemistry, Faculty of Engineering, Istanbul University, 34320 Istanbul, Turkey.
authors.forename: Esma
authors.initials: E
authors.lastname: Tütem
authors.affiliation: Department of Chemistry, Faculty of Engineering, Istanbul University, 34320 Istanbul, Turkey.
authors.forename: Esin
authors.initials: E
authors.lastname: Akyüz
authors.affiliation: Department of Chemistry, Faculty of Engineering, Istanbul University, 34320 Istanbul, Turkey.
authors.forename: Seda
authors.initials: S
authors.lastname: Özen
authors.affiliation: Department of Chemistry, Faculty of Engineering, Istanbul University, 34320 Istanbul, Turkey.
authors.forename: Reşat
authors.initials: R
authors.lastname: Apak
mesh_terms: D002241:Carbohydrates / Q000032:analysis* / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D000067030:Fruit and Vegetable Juices / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000737:chemistry; D019163:Reducing Agents / Q000032:analysis* / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods*; D013395:Sucrose / Q000032:analysis / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D010618:Phenanthrolines; D019163:Reducing Agents; D013395:Sucrose; D003300:Copper; C002701:neocuproine
keywords: Cu(II)-Nc; DNS; Fructose; Glucose; Reducing sugar; Spectrophotometry