Ultrasound-Assisted Intensification of Maillard Reaction Involving Reducing Sugars Obtained from Wheat Straw and Whey Protein Isolate

The current study aimed to generate value-added products through the Maillard reaction between reducing sugars obtained from wheat straw and whey protein isolate (WPI) coupled with process intensification using ultrasound. Optimization of the parameters was performed using a one-factor-at-a-time approach by varying WPI concentration (over the range of 0.5–2.0%), pH (6–10), temperature (50–90 °C), and treatment duration (10–40 min) using the conventional water-bath method. The optimal reaction conditions obtained using the water-bath approach were then applied to the ultrasound-assisted process, in which varying ultrasonic power and duty cycle were evaluated at a fixed sonication frequency. The degree of browning at 420 nm, DPPH radical-scavenging activity, color parameters, and intrinsic fluorescence were analyzed, and all experiments were performed in triplicate. The optimal conditions were 1.5% WPI, pH 9, temperature 80 °C, a treatment time of 30 min, an ultrasonic power of 100 W, and a 60% duty cycle. Under these conditions, ultrasound increased the A420 value from 1.104 to 1.769, corresponding to an approximately 60% increase in browning, and enhanced DPPH radical-scavenging activity by 35% compared with conventional water-bath treatment. The ultrasound-treated sample also showed the highest b* value (2.06) and greater fluorescence intensity than native WPI and the conventionally treated conjugate, indicating enhanced glycation. Overall findings demonstrate that ultrasound can intensify the Maillard reaction while enabling the value addition of sustainable raw materials.