Objective To analyze the effect of ultrasound assisted photocatalytic technology on the Maillard reaction effectiveness and volatile aroma compounds in the isoleucine–glucose (Ile–Glc) system.

Method An Ile-Glc reaction system was constructed, the Maillard reaction products were used as the evaluation indexes, tthe effect of the Maillard reaction effectiveness on single-factor were studied,including light band, photocatalyst types, TiO₂ addition and particle size, temperature, initial pH value and ultrasound. The ultrasonic assisted photocatalysis process was optimized though orthogonal experiments. Finally, the differences of the aroma, taste profiles, volatile aroma compounds and risk factors in Ile–Glc system were analyzed between the samples which treated by ultrasonic assisted photocatalytic and heat treatment respectively, using electronic nose, electronic tongue, gas chromatography mass spectrometry and high-performance liquid chromatography technology.

Result The optimal photocatalytic conditions for photocatalysis were full-spectrum xenon lamp irradiation, TiO₂ as the catalyst, a reactant molar ratio of 1:1, a reaction temperature of 50 °C, and ultrasound power of 150 W. The optimized process were 400 mg/L of photocatalyst addition, 150 nm of photocatalyst particle size, and the initial reaction pH value of 7.0. At optimized ultrasonic assisted photocatalysis conditions, the initial, intermediate and final stages of the Maillard reaction product ΔY, ΔOD₂₉₄ and ΔOD₄₂₀ showed a trend of rising initially and then gradually stabilizing, reaching the stable value 6.3×10⁶ a.u., 3.8 and 0.52 all at 30 days. Ultrasonic assisted photocatalytic treatment can significantly enhance the responses of phenolic compounds (W1C), nitrogen-oxygen compounds (W5S), organic sulfides (W2W), and umami taste in the Ile-Glc system, and reduce the bitter and astringent response values (P＜0.01); produce characteristic volatile aroma compounds of OAV＞1, such as 2,3,5-trimethylpyrazine, 2-methylbutanal, 2-butanone, and 2,4-di-tert-butylphenol, forming a baking and nutty aroma. Compared with heat treatment of 15.5 h, the amount of 2,3,5-trimethylpyrazine with cocoa and roasted fragrance was higher, the amount of 2-methylbutaldehyde, 2,4-di-tert-butylphenol, 2-butanone were lower; the safety risk factors including 5-hydroxymethylfurfural (5-HMF), 3-deoxyglucosone (3-DG), and glyoxal (GO) were only79.57%, 33.33% and 71.43% respectively.

Conclusion The study indicates that ultrasonic assisted photocatalytic treatment can promote the Maillard reaction in the Ile-Glc system, produce the characteristic aroma compounds such as pyrazines, enhance baked aroma, and the risk factors such as 5-HMF was relatively low.