Abstract
This research paper investigates the use of 5-hydroxymethylfurfural (5-HMF) as marker for the heat treatment of spreadable dairy creams (dulce de leche, DL). The proposed method applies solid-phase extraction (SPE) with final analysis by liquid chromatography coupled with high-resolution mass spectrometry (SPE-LC–MS). The method was successfully applied to analyze spreadable dairy creams prepared by hot melt extrusion using different heating temperatures from 100 to 130 °C. The concentrations of 5-HMF correlated linearly with the applied temperatures, with a signal response in the range from 0.5 to 100 μM (R2 = 0.9997). The limit of detection (LOD) was 1.54 ± 0.03 µM with a precision of 1.77%. The results were compared with the analysis of 5-HMF in spreadable dairy creams using reference methods for the determination of 5-HMF in milk products. These methods mainly employed acid digestion and derivatization as pre-processing steps and determined 5-HMF spectrophotometrically and via HPLC–UV. These resulted in higher LOD (2.99 and 2.01 μΜ) and less precision (4.44 and 2.09%) compared to the proposed method. Furthermore, the proposed pre-processing procedure was faster by omitting the acid digestion and derivatization steps and by employing SPE.
Highlights
Spreadable dairy creams are a popular snack food, especially within children
A typical example of spreadable dairy creams is represented by dulce de leche (DL), a brown and sweet cream obtained by the extensive heating of milk, when mixed with sugars and bicarbonate
This study proposes a rapid method to determine the content of 5-HMF in DL samples based on liquid chromatography coupled to mass spectrometry (LC–MS) after solid-phase extraction (SPE)
Summary
5-Hydroxymethylfurfural (5-HMF) was purchased from Sigma-Aldrich (Steinheim, Germany) at purity higher than 99%. Three millilitres of diluted sample were mixed with 1.5 mL oxalic acid solution (0.3 mol L−1). The supernatant containing the watersoluble fraction and the whey proteins was collected and directly subjected to SPE omitting the acid hydrolysis for 23 h foreseen by Resmini et al 0.5 mL of sample was loaded on a preconditioned (15 mL 1:2 MeOH/H2O v/v) C18 SPE cartridge (V = 6 mL, Thermo Sci.) and eluted with 3-mL hydrochloric acid solution (3 mol L−1) until dryness of the cartridge using air flow with an automated SPE system (GX-271 Aspec, Gilson Italia S.r.l, Italy). One millilitre of the eluate was dried under nitrogen flow at room temperature (MultiVap 8, LabTech S.r.l., Milano, Italy) and dissolved in 1 mL of 5% acetonitrile in deionized water and analyzed by LC-HRMS. The mobile phases included solvents A (water with addition of 0.1% trifluoroacetic acid v/v) and B (acetonitrile), and the following gradient: 5% B (v/v) for 7.5 min, from 5% B to 95% B at 8 min, hold until 8.5 min to 5% B at 9 min followed by a re-equilibration step (5% B) from 9 to 10 min
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