Abstract: The Maillard reaction degree of 15 heat-treated milks were evaluated by determining the production of two typical Maillard reaction products, furosine and 5-hydroxymethyl furfural. The change of volatile compounds in the treated samples were investigated by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and electronic nose technology (E-nose). An untreated sample was used as a control. The results showed that greater degree of heat treatment could result in higher degree of Maillard reaction, and the production of furosine and 5-hydroxymethylfurfural increased sharply when the heat treatment temperature was higher than 120 ℃ or the heat treatment time was longer than 15 s. Principal component analysis (PCA) of the E-nose data showed significant odor differences between samples treated at different temperatures for the same duration. GC-MS results showed that the flavor of heat-treated milk at 120 ℃/5 s and 120 ℃/15 s was similar to each other, and as the intensity of heat treatment increased, the number of newly formed flavor substances increased significantly, and the relative contents of aldehydes, ketones and esters increased significantly. On the other hand, the relative contents of some acids significantly dropped. This study corroborated the effect of different heat treatments on the Maillard reaction degree and flavor of milk, which could also provide guidance for milk production.

Key words: heat treatment; Maillard reaction; furosine; electronic nose; headspace solid-phase microextraction-gas chromatography-mass spectrometry