DETECTION OF SUGAR ADDITION TO CITRUS JUICES BY CAPILLARY GC

A method is described for the detection of citrus juices adulterated b y addition of industrial sugar products. The oligosaccharides maltotri ose (DP3) and maltotetraose (DP4), both of which are absent from the n atural sugar profile of citrus fruits, serve as markers. The sample pr eparation method includes clean-up on a solid phase ODS cartridge, fra ctionation of DP3 and DP4 carbohydrates by LC on aminopropyl silica ge l, and derivatization of the collected sugars to form the oxime-trimet hylsilyl derivatives. Capillary GC analysis is performed on a 30 m x 0 .32 mm i.d. polydimethylsiloxane fused silica column applying cool on- column injection and FID detection. The detection limit for maltotrios e and maltotetraose is about 1 mg I-1. Several orange and grapefruit j uices were evaluated on their authenticity. Adulteration with crystall ine sugar products cannot be detected with the described procedure.