Study On Modification Of Tomato Seed Protein

Tomato is one of the most popular vegetable. There are a large amount of tomatoes being processed into tomato-based products like sauces, pastes and kechup every year in China. Besides, the scale of processing is increasing. The content of protein in tomato seeds which is byproducts produced from the processing of tomatoes is high, which makes tomato seed a potential protein source. Tomato seed protein can be extracted with the method of alkali solution along with isoelectric precipitation which is conventional. However, the functional properties of tomato seed protein are poor. This study focuses on the protein modification, aiming at exploring utilization means for tomato seed protein, providing theory basis for exploiting and utilizing tomato seed protein.The work was done to investigate the effects of freeze drying and spray drying on the functional properties and structure of tomato seed protein which was prepared by alkali extraction and acid precipitation. The solubility, emulsifying ability and foaming ability of tomato seed protein isolates dried by spray drying(SD-TSPI) is better than that of tomato seed protein isolates dried by freeze drying(FD-TSPI), while FD-TSPI has higher water/oil holding capacity. The surface hydrophobicity and the S-S content of SD-TSPI are higher than that of FD-TSPI, while crystal structure and subunits composition show no difference between FD-TSPI and SD-TSPI. The composition of secondary structure in SD-TSPI and FD-TSPI are different. In FD-TSPI, the content of β-turn is higher than that of SD-TSPI, while the contents of β-sheet and random coil are lower than that of SD-TSPI, which shows that the freeze drying method can reserve native protein structure better. The choice of drying method could significantly influence protein structure, consequently determining the functional properties.Micro-fluidization treatment was choosed to modify the tomato seed protein isolate(TSPI). The effect of micro-fluidization treatment on structure and functional properties of TSPI was investigated. It was found that microfluidization can significantly improve the solubility and emulsifying ability, and change the particle size of TSPI; the content of exposed sulfhydryl and total sulfhydryl decreased; the hydrophobic group in protein molecules exposed which result in increased surface hydrophobicity; the changes in protein crystal structure is too little to be noticed. As for the changes in secondary structure, it caused an increase in β-turn and random coil at the expense of β-sheet. The maximum change was showed when TSPI was treated at 130 MPa. Protein functional properties are changed after microfluidization treatment may due to the fact that micro-fluidization treatment unfolded or aggregated the protein molecular.Various proteased were used to hydrolyze directly tomato seed protein concentrate, and the effects of enzymatic modification on functional properties of tomato seed protein(TSP) were investigated. Enzymatic hydrolysis of TSP can significantly improve protein functional properties and protein content. The hydrolytic process of tomato seed protein with different proteases were similar, the degree of hydrolysis increased with the hydrolysis time. The degree of hydrolysis of five different TSPHs in equal times varied with the proteases, which indicated that the hydrolysis efficiency of proteases is different. According to the result, the hydrolysis efficiency of alcalase is highest among them. While papain was more effective in recovering of protein reached to 81.12%. The functional properties and antioxidant activity varied with the protease.The maillard reaction was used to midify tomato seed protein. The functional properties of maillard reaction products were investigated. The results showed that pH values decreased as the heating time increased; the absorbance at 420 and 294 as well as the solubility and emulsifying ability increased; the surface hydrophobicity of maillard reaction products were higher than that of tomato seed protein. However, it decreased as the heating time increased. In a word, maillard reaction can improve the functional properties of tomato seed protein.