Hi, Chloe! We have yet to ever receive this feedback/experience happening with our syrups! Did you happen to combine the syrup with the milk when steaming? Curdling can be prevented by mixing the syrup directly with the espresso first, then adding in the steamed milk (the milk's freshness or overheating can also be the reason). Otherwise it may be due to the acidity creating a natural occurence (though rare), and should not affect the flavor whatsoever! Regardless, we're sad to hear you did not enjoy the flavor and completely understand they may not be for everybody!