Soy protein isolate (SF!) was extracted from soy flour and hydrolyzed with hydrochloric acid, sodium hydroxide, and enzyme, separately, to provide a series of hydrolysates. The SPI and its hydrolysis products were later cross-linked with ethylendiaminetetraacetic acid (EDTA) in the presence of sodium hypophosphite (SPH) after which they were complexed to chitosan as part of an on-going general chemical strategy in our laboratories to improve their incorporation into old corrugated container (OCC) matrix and thus increase inter-fiber bonding. Approximately 2% SPI-EDTA-chitosan and hydrolyzed SPI-EDTA-chitosan additives by mass (OCC-based slurry) were thoroughly mixed before generating a sheet for physical testing. The tensile and burst indices of the SPI-EDTA-chitosan additive-treated OCC pulp sheet increased 46.3% and 61.85%, respectively, while the inter fiber bonding of SPI-EDTA-chitosan additive-treated OCC pulp sheet increased 74.86% compared to the control, albeit having a decreased tear strength and roughness, with significantly increased gloss. The additive-treated pulp sheet was characterized by thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and ATR to provide evidence for product synthesis. (C) 2014 Elsevier B.V. All rights reserved.