Effects and Mechanisms of Ultrasonic Pretreatment on the Maillard Reaction in Bovine Bone Protein Hydrolysates

To valorize protein-rich bovine bone, a meat processing by-product, this study investigated the effect of ultrasonic pretreatment on the Maillard reaction (MR) of bovine bone hydrolysates. The underlying mechanism was elucidated by analyzing the hydrolysate microstructure, peptide molecular weight distribution, and free amino acid content. Furthermore, the extent of the reaction and the flavor characteristics of the resulting Maillard reaction products (MRPs) were evaluated. The results indicated that ultrasonic treatment significantly disrupted the spatial structure of the bovine bone protein compared to the control, thereby increasing the proportion of low molecular weight peptides (<500 Da) to 70.96%. This structural alteration intensified the MR. Concurrently, the free amino acid consumption rate reached 59.15%, which significantly promoted the formation of key flavor compounds. Moreover, ultrasonic treatment enhanced the sourness, saltiness, and overall intensity of the MRPs while reducing bitterness. The increase in volatile compounds such as furfural (1.53 µg/L), benzaldehyde (4.64 µg/L), and 2-methyl-3-furanthiol (0.65 µg/L) improved the overall flavor profile of the MRPs. Consequently, ultrasonic treatment enhances the utilization of flavor precursors, advances the progression of the MR, and provides a theoretical foundation for developing high-quality, functional bone-derived seasonings.