Changes in Flavor Substances of Sauced Beef during Processing Based on the Maillard Reaction

In this study, sauced beef was prepared by three different cooking processes: ultrasonic-assisted stepwise cooking (CF), stepwise cooking (F) and traditional cooking (CT). In order to investigate changes in the flavor substances of sauced beef during different cooking processes, the effect of the three cooking processes on the flavor of sauced beef were analyzed from the perspective of the Maillard reaction. Absorbance at 294 nm (A_{294 nm}) and 420 nm (A_{294 nm}), which can reflect the amount of Maillard reaction products (MRPs) formed in the middle and late stages, respectively, were measured. The results showed significant differences in A_{294 nm} between the CF and CT groups at 0.5 h of cooking (P < 0.05), but no significant differences between the CF and CT groups at 2 and 4 h (P > 0.05). A_{294 nm} and A_{420 nm} were significantly higher in the F group than in the CT and CF groups at 0.5 and 4 h. The CF group had the highest fluorescence intensity. Protein secondary structure analysis indicated an increase in the relative content of β-sheet and a decrease in the relative content of α-helix in the CF and F groups compared with the CT group; α-helix unfolding led to the exposure of intramolecular hydrophobic groups, thereby increasing the surface hydrophobicity and fluorescence intensity. Ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) identified 103, 167, and 200 differential metabolites in the CT, F, and CF groups, respectively, and a large number of amino acids, dipeptides, nucleosides, and heterocyclic compounds were produced in the CF group; gas chromatography-mass spectrometry (GC-MS) results showed that CF and F promoted the production of volatile flavor substances in sauced beef. The above results indicated that both cooking processes could promote the Maillard reaction and consequently improve the flavor of sauced beef.