Lactose, galactose and glucose determination in naturally “lactose free” hard cheese: HPAEC-PAD method validation

•A sensitive method for lactose, galactose and glucose determination is optimized.•Anionic chromatography with pulsed amperometric detector is applied.•The performances are tested on long ripened PDO Grana Padano cheese.•Results show that all the sugars are quite completely metabolized in cheese.

A chromatographic method by HPAEC-PAD was developed and in-house validated for the quantification of low sugar levels in hard cheese, specifically Grana Padano PDO cheese. Particular attention was paid to the extraction procedure, due to residual microbial and enzymatic activities. Specificity in detection and linearity were verified. Recoveries ranged from 93% for lactose to 98% for glucose and galactose. The obtained LOD and LOQ values were, respectively, 0.25 and 0.41 mg/100 g for lactose, 0.14 and 0.27 mg/100 g for galactose, and 0.16 and 0.26 mg/100 g for glucose. The method was applied to 59 samples of Grana Padano PDO cheese: galactose showed the highest concentration and variability among the samples (1.36 ± 0.89), compared to both lactose (0.45 ± 0.12) and glucose (0.46 ± 0.13). Considering the very low levels of sugars detected, authentic PDO Grana Padano could be safely included in the diet of people suffering from lactose intolerance.