The acid-soluble protein (AP) and alkali-soluble protein (BP) from cold-pressed pecan cake were separated using the pH-shifting method, and the functional properties of AP and BP were analyzed.The optimal conditions for the extraction of AP and BP from pecan cake were determined based on protein dissolution rate and precipitation recovery.The pH of 2.0 and 12.0 were found to be the optimal dissolution conditions of AP and BP, resulting in dissolution rates of 4.79% and 53.01%, respectively.For precipitation recovery, the optimal conditions of AP and BP were pH 12 and pH 3, with protein recovery rates of 70.09% and 99.88%, respectively.The molecular weights of AP were distributed below 22 kDa, while those of BP subunits were aggregated at 20 kDa, 39 kDa, and 45 kDa, based on the results of SDS-PAGE.The contents of free sulfhydryl groups and disulfide bonds of AP were 16.6 and 1.40 μmol/g and the contents of free sulfhydryl groups and disulfide bonds of BP were 14.58 and 1.34 μmol/g.AP had the highest solubility of 76.77% at pH 3, while BP had the highest solubility of 94.75% at pH 11.AP retained more water than BP, while BP had better oil holding capacity.Additionally, the foaming and emulsifying capacities of BP were higher than those of AP.The scanning electron microscope results showed that BP exhibited a large lamellar structure with a smooth surface, while AP displayed an irregular shape with honeycombs and holes on the surface.The results of the study illustrated that AP was suitable for application in acidic food products such as milk and acidic beverages, while BP was recommended for the ice-cream, bread, and cakes which require higher foaming properties.
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