The Preparation Of Okara Protein(OP) And Study On Interaction Between OP And Carboxymethyl Cellulose(CMC)

China is rich in okara,with an annual output of 2.8 million tons.Okara contains 14~30% protein and 40~80% dietary fiber,making it a suitable source of protein and dietary fiber.Okara protein(OP)have all essential amino acids required by human body and high nutritional value.However,in okara,OP usually combines tightly with non-starch polysaccharides such as soybean cellulose,hemicellulose,lignin,etc.,which makes it difficult to separate from okara.Besides,OP have poor functional properties,especially solubility and emulsifying ability,resulting in limited application.The aim of this paper is to explore an effective way to separate OP from defatted okara with good solubility and emulsifying ability,and focuses on the interaction between OP and carboxymethyl cellulose(CMC)and its mechanism in aqueous system,oil-water interface and emulsion system.Firstly,different pretreatments(homogenization,ultrasound and steam-cooking treatments)and different acids(HCl,citric acid and malic acid)during acid-precipitate process were used to extract OP from defatted okara,and their effects on the structure and fuctional properties of OP were studied.According to the results,OP with good functional properties was obtained.Then this reaearch explored the effects of pH(7.0,4.0 and 3.0)and CMC concentration(0~0.5 wt%)on the interaction of OP-CMC in different systems(aqueous system,oil-water interface and emulsion system).The mechanisms of emulsion stabilization and instability were uncovered,providing more theoretical basis for the development of food additives prepared by OP and the improvement of added value of okara.Different pretreatments and acid type significantly affected the structure and functional properties of OP.Results showed that the main subunit components of OP were 7S,11 S and Bg 7S globin.In addition,OP obtained without pretreatments showed good solubility and emulsifying ability than that of obtained by pretreatments.It should also be noted that OP precipitated by malic acid had the hightest surface hydrophobicity of 1032.70,and its solubility and emulsifying ability index were 69.77% and 83.69%,respectively,which were 47.53% and 47.86% higher than that of commercial SPI,respectively.pH and CMC concentration apparently changed oil-water interfacial properties of OPCMC.Results demostrated that under neutral condition,there was no adsorption between OP and CMC,and CMC had little effect on interface characteristics of OP.Nevertheless,CMC constantly adsorbed on the surface of OP with the increase in CMC concentration,under acidic conditions.Furthermore,OP-CMC aqueous system could stay stable when CMC concentration was equal to or higher than 0.2 wt% under pH 4.0,while under pH 3.0,the system could remain stable only when CMC concentration was up to 0.5 wt%.It was also revealed that CMC leaded to change in surface pressure and viscoelasticity of OP-absorbed film under acidic conditions.pH and CMC concentration distinctly influenced the stability of OP-CMC-stabilized emulsion.Results suggested that under pH 7.0,OP-stablized emulsion had good storage stability and emulsions became unstable after the addition of CMC because of flocculation.But the stability of OP-CMC emulsions enhanced with increasing CMC concentration.Under pH 4.0,CMC obviously improved emulsion stability while under pH 3.0,the emulsion was still unstable due to droplet aggregation even when CMC concentration reached 0.5 wt%.