Improved backward extraction of walnut protein using AOT reverse micelles with microwave and its characteristics

The extraction of walnut protein (WP) was carried out using sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles with microwave-assisted backward extraction (MABE), which was potential to improve the extraction yield of WP. And the functional and structural properties were determined. The optimized conditions by response surface methodology were extraction time 30 min, extraction temperature 45°C, and aqueous solution to forward extraction solution ratio 3:1 (vol/vol), the backward extraction yield reached 95.43 ± 2.08%. WP from MABE exhibited the higher solubility (68.35 ± 0.67%), oil absorption capacity (2.43 ± 0.21 g/ml), water holding capacity (2.78 ± 0.02 g/ml), foam capacity (64.03 ± 1.20%), foam stability (72.17 ± 3.05%), emulsifying activity index (3.24 ± 0.86 m2/g), and emulsifying stability index (70.20 ± 0.21 min). FTIR revealed that the main backbone structure changes of WP after microwave treatment did not occur, there was a small change of protein structure, with the increase of α-helix and random coil proportions, decrease of β-turn and similar β-sheet content. Practical applications A novel microwave-assisted backward extraction method of reverse micelle was developed. The backward extraction yield and functionality of walnut protein (WP) with this method could be improved. This work have the potential for promoting the application of reverse micelles in the food industry.