Abstract: The chemical modification of soybean protein with urea, sodium hydroxide, and methy1dichlorosi1ane and the plasticization of the modified soy protein isolate using glycerol, polyethylene glycol, sorbitol, caprolactam, and ethyl amide. The structure of modified soy protein isolate was characterized，and the thermal, mechanical, and rheological properties as well as water resistance of the modified soy protein isolate were studied. The long chain of protein could be cut effectively by alkali which increased the processability of protein. The hydrophilic group in the protein molecules could be reacted off or covered by urea and dimethyldichlorosilane, so the water resistance of the materials was increased. Polyethylene glycol and caprolactam were proven effective plasticizers.

Key words: soy protein isolate, chemical modification, long chain, plastication, flow ability