Research of the determination method of furfurals and furosine in milk and the application in the quality evaluation of milk

The heat treatment process usually affects the quality and safety of milk and could produce different compounds, including furosine and furfurals. To help evaluate the effect of different heating temperatures on furfurals, a method based on gas chromatography-mass spectrometry (GC-MS) combined with QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction technology was used to detect four furfural compounds, including furfural, 2-acetylfuran, 5-methyl-2-furfural, and 5-hydroxymethyl-2-furfural. A sample extraction was performed with acetonitrile, and the use of both octadecylsilyl (C18) and primary secondary amine (PSA) sorbents can provide satisfactory recoveries. The determination of furosine was performed by using a high performance of liquid chromatography method (HPLC), and the milk samples were hydrolyzed with HCl for 18 h at 110°C. Under the optimized conditions, good linearity was obtained with linear correlation coefficients (R2) above 0.99, and the recovery values from the spiked samples were 88.1–109.5%. The limits of detection were in the range of 0.005 mg/kg–0.015 mg/kg. The established GC-MS and HPLC methods were successfully applied to market milk samples and heat-treatment samples. The highest detection values for 5-hydroxymethyl-2-furfural and furosine were 0.051 mg/kg and 593.2 mg/100 g protein, respectively, in charcoal-flavored fermented milk. It showed a high correlation between the formation of 5-hydroxymethyl-2-furfural with the treatment temperature and time, and the maximum content was 0.886 mg/kg after heating for 180 min at 100°C. However, there was no noticeable linear increase of furosine concentrations when certain temperatures and heating times were reached; the maximum value was 55.0 mg/L after heating for 60 min at 100°C, and 55.4 mg/L after heating for 150 min at 80°C.