Structural And Functional Properties Of Walnut Protein Obtained From Chinese Four Varieties

Walnut(Juglans)with many variteies has a great production and a wide area in China.As a common oil crops walnut is usually used to produce edible walnut oil.After oil pressed there are a large amount of by-product-walnut meal,which is rich in proteins and amino acids composed reasonable.Four representative walnut varieties were seclected and pressed to make walnut oil by cold and hot hydeulic pressing method,respectively.Walnut meal was used as raw material to extract walnut protein.The component composition,structural and functional properties among cold and hot pressed protein were compared and analyzed.The study was aimed to provide reference for further developing of walnut protein deep-processing products according to walnut protein characteristics.The main results show as follows:(1)The compositions,amino acid and subunit of walnut protein were determined.There was no significant differences in protein,fat and water content among different varieties of walnut protein(WP).The content of water and protein in cold-pressed walnut protein(CPWP)was significantly higher than that in hot-pressed walnut protein(HPWP),and the content of fat was significantly lower than that in HPWP.Diferent walnut protein showed a significant difference in amino acid composition.Yangbi HPWP and J.mandshurica Max had the high degree of similarity to the FAO/WHO model protein with a good nutritional value.There was no significant difference in the subunit bands from the result of SDS-PAGE of different WP varieties,while the changes between CPWP and HPWP did not significantly.(2)The differences of structural of CPWP and HPWP were analyzed,HPWP showed a less compact structure than CPWP,Zha 343 CPWP structure was relatively compact,while J mandshurica Max.and Yangbi HPWP structure were more loose.Fluorescence spectrum results showed that the maximum fluorescence emission peak(?m)of HPWP had redshift,the most obvious redshift appeared in J.mandshurica Max.HPWP.Surface hydrophobicity(HO)of HPWP was higher than CPWP and J.mandshurica Max showed the higest H0.Denaturation temperature(To)of Zha 343 CPWP was the highest up to 102.6?.(3)The functional properties of CPWP and HPWP were analyzed.There was no significant difference in the solubility of WP between different varieties.HPWP had lower solubility than CPWP.The water and oil absorbency of CPWP were significantly higher than HPWP.Yangbi,Xiangling and Zha 343 HPWP showed the less in vitro digestibility by pepsin and trypsin than CPWP except J.mandshurica Max.Among all samples Zha343 CPWP had the best solubility,foaming and emulsifying properties,while J.mandshurica Max HPWP showed opposite results,Xiangling HPWP had the best water and oil absorbency.