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Defatted wheat germ is a highly nutritious protein, which contains about 30% protein. In this study, defatted wheat germ (DWG) protein was used to form coacervate with apple pectin. Structural transition during coacervate formation was evaluated by ζ-potential, spectrophotometry, and light scattering as a function of pH (2.0-6.0), protein to polysaccharide ratio (DWG protein-Pectin, R=1:1, 2:1 and 4:1) and total biopolymer concentration (0.5 and 1%). Furthermore, the phase changes of DWG protein-pectin complex coacervate was studied by checking the turbidity during the time. The best ratio of DWG protein/pectin for complex coacervation was found 4:1 (Pr:Ps). The critical pH affiliated with forming of soluble and insoluble complexes (respectively pHc and pHf1) at the optimum DWG protein/pectin ratio were found 6.0 and 4.9, respectively. The most interaction, the most turbidity, was found at pH=4.0. The inconsistency and liquidation of DWG protein/pectin complex coacervates initialized at pH=2.0. Particles size of DWG protein/pectin (R=4:1, CT=1 %) measured by dynamic light scattering (DLS) at critical pH values, provided further insight into the segregate and associative processes during complex coacervation. The findings can be contributed to the development of DWG protein/pectin complex coacervates as delivery systems for volatile aromas, or bioactive compounds. [ABSTRACT FROM AUTHOR]