Dual Modification of Manila Tamarind Protein Isolate by Ultrasonication and Autoclaving and Their Characterization

Present investigation evaluated physicochemical and functional properties of Manila tamarind seed flour and seed protein isolate. Seed flour was defatted using petroleum ether (bp 40–60 °C) and used for preparation of protein isolate by alkaline extraction followed by isoelectric precipitation. Protein content in the seed flour was 32.59 ± 2.05% and 85.17 ± 0.31% in seed protein isolate. Protein isolates were treated with ultrasound (180W and 35 kHz) and autoclave (121℃ and 15psi) alone and in combination for 15 and 30 min, respectively. The autoclave treatment resulted in reduction of emulsification properties, protein solubility, and water and oil absorption capacity of the protein isolate but the same properties got enhanced with ultrasound treatment. Bulk density of samples increased with both treatments. The combination of treatments resulted in enhancement of all functional properties studied except bulk density and particle density. The values of protein solubility and water and oil absorption capacity of seed protein isolate increased from 64.11 ± 0.37% (native), 166.66 ± 2.51% (native), and 171.33 ± 1.52% (native) to 78.45 ± 1.04% (modified), 194 ± 1.73%, and 206 ± 4.00%, respectively, after autoclave and ultrasound treatments. Emulsifying activity and emulsion stability ranged between 56.47 ± 0.65% (native) to 78.19 ± 0.72% (modified) and 52.54 ± 0.80% (native) to 68.76 ± 0.81% (modified). SDS-PAGE pattern of the seed protein isolate (native and modified) revealed distinct dark bands between 50 and 90 kDa and certain fragmented bands in some of the modified samples. High molecular weight proteins were found to be stable towards the autoclave and ultrasound treatments, whereas low molecular weight proteins(~ 14–16 kDa and < 10 kDa) were slightly affected.