Effect of ultrasonic treatment on the graft reaction between soy protein isolate and gum acacia and on the physicochemical properties of conjugates.
Soy protein isolate (SPI) was grafted with gum acacia (GA) in this work. In comparison with classical heating at high water activity, ultrasound could accelerate the graft reaction between SPI and GA. A degree of graft (DG) of 34 was obtained by ultrasonic treatment for 60 min, whereas 48 h was required with classical heating. Ultrasonic treatment improved the concentration of available free amino groups of SPI. The grafted SPI showed significantly (p < 0.05) higher levels of emulsifying activity index, emulsifying stability index, and surface hydrophobicity than native SPI. The droplet size (D[3,2] and D[4,3]) of SPI emulsion decreased from 8.3 to 2.3 microm and from 25.7 to 7.1 microm through ultrasound-assisted grafting, respectively. Moreover, SPI-GA conjugates gave emulsions exhibiting more stability against creaming than those prepared with only SPI during ambient temperature storage (20 days). Decreases of lysine and arginine contents during the graft reaction indicated that these two amino acid residues attended the covalent linkage between SPI and GA. The results of secondary structure suggested that grafted SPI had decreased alpha-helix and beta-sheet levels and increased unordered coils level.
College of Light Industry and Food Sciences, South China University of Technology, Guangzhou, People's Republic of China.
Lixia
L
Mu
Mouming
M
Zhao
Bao
B
Yang
Haifeng
H
Zhao
Chun
C
Cui
Qiangzhong
Q
Zhao
D055598:Chemical Phenomena; D005524:Food Technology / Q000379:methods*; D006170:Gum Arabic / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D011487:Protein Conformation; D030262:Soybean Proteins / Q000737:chemistry* / Q000302:isolation & purification*; D014465:Ultrasonics
D030262:Soybean Proteins; D006170:Gum Arabic