Does oxygen catalyze the decomposition of sucrose?
If any sucrose hydrolysis were occurring due to oxygen as a factor, it's more likely due to acids formed as it oxidizes species in the solution (for example, alcohol groups to carboxyls), which conceivably could include sucrose itself. But, it seems more likely that the $\ce{CO2}$ in air would be a factor because $\ce{CO2}$ dissolution increases the acidity of the solution, in addition to any other acids present (citric, for example). 

However, sucrose hydrolysis is really slow unless the acidity and/or heat is significant ($\mathrm{pH} &lt; 0$, or heat near boiling), so I doubt either of these explanations, unless these are really old, and/or had been heated.  More likely the glucose was there in the first place.

The way to properly answer this question would be to do control studies in which known amounts of sucrose and acid are initially present and tested with or without exposure to air having varying amounts of oxygen and carbon dioxide.