title: Determination of D-malic acid in apple juice by liquid chromatography: collaborative study.
abstract: Eleven laboratories collaboratively studied a liquid chromatographic (LC) method for determination of D-malic acid in apple juice. The mobile phase consisted of mM L-valine and 8 mM copper acetate adjusted to pH 5.5 with NaOH. The UV detector was set at 330 nm, and a single reversed-phase LC column was used. Seven paired samples containing various amounts of D-malic acid ranging from 0 to 188 mg/100 mL of 12 Brix pasteurized apple juice were tested by each collaborator. Repeatability and reproducibility coefficients of variation ranged from 1.0 to 3.5% and 7.7 to 11.7%, respectively, within the range of 26 to 188 mg D-malic acid/100 mL of 12 Brix apple juice. The collaborative study results demonstrated that the method could quantitate the economic adulteration of apple juice with DL-malic acid at lower levels than those reported with previous methods. The LC method for determination of D-malic acid in apple juice has been adopted first action by AOAC INTERNATIONAL.
authors.affiliation: Tree Top, Inc., Technical Center, Selah, WA 98942, USA.
authors.forename: T A
authors.initials: TA
authors.lastname: Eisele
mesh_terms: D001628:Beverages / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005503:Food Additives / Q000032:analysis*; D005638:Fruit; D008293:Malates / Q000032:analysis*; D012680:Sensitivity and Specificity; D013237:Stereoisomerism
chemical_list: D005503:Food Additives; D008293:Malates; C030298:malic acid