Lactose detection and quantification in milk by gold nanoparticles-based surface-assisted laser desorption/ionization mass spectrometry technique

Abstract

Lactose, or milk sugar, is one of the essential carbohydrates included in the human diet. Its most significant source is milk and other dairy products. Still, due to the ever-increasing percentage of the population with lactose intolerance, there is a need to detect and quantify it in food products. Surface-assisted laser desorption/ionization mass spectrometry (SALDI MS) method on gold nanoparticle enhanced steel target (AuNPET) was used to rapidly detect and quantify lactose with a minimum sample pretreatment including molecular weight cut-off ultrafiltration. The carbohydrate was tested directly in the concentration range from 500 µg/mL to 1 µg/mL, which corresponds to 1.46 nmol to 2.92 pmol per analyzed spot. Limit of detection (LOD) of 0.14 µg/mL or 0.42 µM is one of the best among the techniques used to determine lactose. In addition, the quantitative approach based on mass spectrometry of milk samples shown in this study made it possible to decide on lactose concentration in real samples.