Microfluidization treatment improve the functional and physicochemical properties of transglutaminase cross-linked groundnut arachin and conarachin

Improved gelation, thermal stability and water holding properties have been observed in transglutaminase (TGase) cross-linked (TC) proteins, however, TGase cross-linking would inevitably lead to a decrease in solubility and emulsifying properties. This study explored the effects of microfluidization treatment (MT) on the solubility, emulsifying and physicochemical properties of TC-arachin/conarachin. The results showed that the protein solubility, emulsion activity and stability of TC-arachin and TC-conarachin significantly increased after MT. Although the SDS-PAGE analysis revealed only slight changes in arachin (S2 - S5) and conarachin (S1) subunits, the molecular weight distribution and microstructure analysis showed a dissociation of large aggregates into small size clumps in TCMT-linkings after MT. It was found that the surface hydrophobicity (H0) values of TC-arachin/conarachin significantly increased from 2826.7 ± 49.3/4005.3 ± 41.5 to 3918.5 ± 79.5/4542.2 ± 68.4 (p < 0.05) whereas the Z-average size declined from to 508.1 ± 4.5/175.7 ± 0.6 to 197.9 ± 1.1/155.9 ± 0.9 (nm, p < 0.05) after MT. Moreover, the increased free sulfhydryl (SH) content was observed in MT-treated TC-arachin/conarachin, which may be caused by the conformation changes of TC-arachin/conarachin. Circular dichroism spectroscopy showed a slightly decrease in α-helix and β-sheet, and a mild increase in β-turns and random coil of TCMT-arachin/conarachin. Together, our findings not only uncover the effects of microfluidization treatment on improving the poor solubility of crosslinking products with excellent functional properties, but also highlight the potential application prospects for arachin and conarachin as the emulsifying and water-retaining agents in processing and storage in the food industry.