Utilizing Dry-Heating Maillard Reaction Approach to Modify the Functional and Structural Properties of Ultrasound Pretreated Sunnhemp Protein Isolate with Dextran

Sunnhemp protein isolate (SHPI) was prepared by utilizing alkaline extraction and acid precipitation method, followed by ultrasound treatment at 50% amplitude for 20 min having fixed power, frequency, and pulse ratio of 500 W, 20 kHz, 15 s, respectively. The ultrasound pretreated SHPI was conjugated with dextran (1:1 w/w ratio) by dry-heating method of Maillard reaction at 60 °C for 0, 1, 3, 5, 7, and 9 days of incubation at 79% relative humidity. The functional properties of SHPI-dextran conjugates like solubility, emulsifying, foaming, water- and oil-binding capacities, dispersibility, and gelation were improved as compared to pure SHPI. Increments in browning index values of SHPI-dextran conjugates were observed with an increase in Maillard reaction time. The α-helix content of conjugated SHPI reduced, while the β-sheet, β-turn, and random coils content increased. FTIR spectroscopy confirmed the formation of covalent bonds between SHPI and dextran via Maillard reaction. XRD analysis indicated both the semicrystalline and amorphous structure of SHPI-dextran conjugates as the incubation time was increased from 0 to 9 days. The decreasing trend in the values of H₀ values was found with an increase in incubation time. Free and total sulfhydryl content of SHPI was increased after conjugation with dextran for up to 5 days and thereafter decreased. The incubation time of 5 days at 60 °C and 79% RH was optimized on the basis of improvement in functional characteristics and extent of Maillard reaction time. Overall, the present study showed that conjugation with dextran successfully improved the functional characteristics of SHPI.