title: Validation of an HPLC method for direct measurement of steviol equivalents in foods.
abstract: Steviol glycosides are intense natural sweeteners used in foods and beverages. Their acceptable daily intake, expressed as steviol equivalents, is set at 0-4 mg/kg body weight. We report the development and validation of a RP-HPLC method with fluorometric detection of derivatized isosteviol, formed by acid hydrolysis of steviol glycosides. Dihydroisosteviol was used as an internal standard. Using this method, the amount of steviol equivalents in commercial steviol glycoside mixtures and different foods can be directly quantified. The method was successfully tested on strawberry jam, low-fat milk, soft drink, yogurt and a commercial mixture of steviol glycosides. Calibration curves were linear between 0.01 and 1.61 mM steviol equivalents, with a quantification limit of 0.2 nmol. The % RSD of intra-day precision varied between 0.4% and 4%, whereas inter-day precision varied between 0.4% and 5%, for high and medium concentrations, and between 3% and 8% for low concentrations. Accuracy of the analysis varied between 99% and 115%.
authors.affiliation: Laboratory of Functional Biology, Kasteelpark Arenberg 31, Box 2436, B-3001 Leuven, Belgium.
authors.forename: Uria
authors.initials: U
authors.lastname: Bartholomees
authors.affiliation: Laboratory of Functional Biology, Kasteelpark Arenberg 31, Box 2436, B-3001 Leuven, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Struyf
authors.affiliation: Laboratory of Functional Biology, Kasteelpark Arenberg 31, Box 2436, B-3001 Leuven, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Lauwers
authors.affiliation: Laboratory of Functional Biology, Kasteelpark Arenberg 31, Box 2436, B-3001 Leuven, Belgium.
authors.forename: Stijn
authors.initials: S
authors.lastname: Ceunen
authors.affiliation: Laboratory of Functional Biology, Kasteelpark Arenberg 31, Box 2436, B-3001 Leuven, Belgium. Electronic address: Jan.Geuns@bio.kuleuven.be.
authors.forename: Jan M C
authors.initials: JMC
authors.lastname: Geuns
mesh_terms: D001628:Beverages / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D045786:Diterpenes, Kaurane / Q000737:chemistry*; D006027:Glycosides / Q000032:analysis*; D008958:Models, Molecular; D013549:Sweetening Agents / Q000032:analysis / Q000737:chemistry*
chemical_list: D045786:Diterpenes, Kaurane; D006027:Glycosides; D013549:Sweetening Agents; C515747:isosteviol; C012042:steviol
keywords: Fluorescence; HPLC; Isosteviol; Steviol equivalents; Steviol glycosides