title: Enzymatic reactions for the determination of sugars in food samples using the differential pH technique.
abstract: All ATP coupled reactions, when performed at neutral or moderately alkaline pH, produce an acidification of the reaction mixture. The detection of small pH changes--0.1 mpH (1 mpH = 10(-3) pH)--in a constant buffering capacity solution makes it possible to quantify, over a wide concentration range (1-1500 mmol L(-1)), various analytes with very high precision and accuracy. Glucose, fructose, glycerol and gluconic acid can be analysed in less than 1 min with a single step reaction. Wine samples were analysed using the hexokinase reaction for glucose + fructose (sugars undergoing fermentation) and compared against an established method, showing excellent performance over the whole range of concentrations (R = 0.9994). Increased sensitivity in some applications can be obtained by cycling reactions, e.g. a kinase reaction followed by a phosphatase reaction. in a one step analysis, as required for lactulose assay in milk, a useful indicator of heat treatment damage. A sensitivity well below 0.1 mmol L(-1) in the original milk sample has been demonstrated.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biomediche, Università di Milano, Milan, Italy. Massimo.Luzzana@unimi.it
authors.forename: M
authors.initials: M
authors.lastname: Luzzana
authors.forename: D
authors.initials: D
authors.lastname: Agnellini
authors.forename: P
authors.initials: P
authors.lastname: Cremonesi
authors.forename: G
authors.initials: G
authors.lastname: Caramenti
mesh_terms: D000818:Animals; D005285:Fermentation; D005632:Fructose / Q000032:analysis*; D005947:Glucose / Q000032:analysis*; D006593:Hexokinase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007792:Lactulose / Q000032:analysis; D008892:Milk / Q000737:chemistry; D014920:Wine / Q000032:analysis*
chemical_list: D005632:Fructose; D007792:Lactulose; D006593:Hexokinase; D005947:Glucose