Unwanted Sucrose Hydrolysis - HPLC-RI

[HalesCB]

Hello,
We are analysing sugars via HPLC-RI in beer samples using a Phenomenex Luna Omega Sugars column.
We run isocratically at 75% acetonitrile with the column and RI set to 40C.

Beer samples are run neat with just the IS spike.

When we spike a 1g/L mixture of sugar standards in to our beer samples, we are seeing hydrolysis of the sucrose in some of the samples. Total sugar recovery is ~100%, it's just transferred over to the glucose and fructose peaks.
It doesn't happen with every beer sample run, just some of them.
It does not happen in wine samples.

We have checked the pH of the beer and overall, pH is higher than that of wine samples.

Trying to figure out why it happens in the first place and why it doesn't happen in every beer.

Any thoughts on the matter would be appreciated!
Thanks

[DR]

Live yeast making it through, or at least some of the enzyme that begins the fermentation process? I'm thinking an initial heating of your samples would stop this. Just get them warm enough to denature any stray enzymes.