Capillary gas chromatographic detection of invert sugar in heated, adulterated, and adulterated and heated apple juice concentrates employing the equilibrium method

The equilibrium method is introduced for the detection of invert sugar addi tion to apple juice. The method consists of a pre-equilibration of the samp le with dry pyridine at 50 degrees C for 20 min followed by the addition of trimethylsilylimidazole and heating at 75 degrees C for 40 min. The result ing derivatized carbohydrates are then analyzed by capillary gas chromatogr aphy. This method was successfully used by independent laboratories to dist inguish heated pure, intentionally adulterated (with invert sugar), and int entionally adulterated and then heated apple juice concentrates. The equili brium method was shown to give significantly lower coefficients of variatio n for this sample set when compared to the original capillary gas chromatog raphic method. In addition, these results indicate that it may also be an e ffective method for the detection of medium invert sugar, depending on the level of the fingerprint oligosaccharides in this sweetener.