Foaming properties of soybean protein-based plywood adhesives

A study was conducted to evaluate the potential of soy protein-based plywoo d glues for foam extrusion. Foaming properties were the first criterion use d to screen several soy protein sources. Foaming capacities and stabilities of glue mixes containing animal blood (control) or soy products (meals, fl ours, concentrates, and isolates) were compared and correlated with molecul ar weights and surface hydrophobicity indices (S-O) in an attempt to identi fy structure/function relationships. The blood-based glue mix produced more foam than any of the soy-based glues. Soy flours and concentrates generall y produced greater foam Volumes and more stable foams than soy meal and iso lates. Differences in foaming properties could not be explained by solubili ty profiles or S-O. However, results of gel electrophoresis indicated that soy products with poor foaming properties had extensive structure modificat ions or contained considerably lesser amounts of protein available for foam ing reactions. Glue mixes containing the soy flours ISU-CCUR, Honeysoy 90, Nutrisoy 7B, and defatted Soyafluff and the soy concentrates Arcon F, ISU-C CUR, and Procon 2000 demonstrated the desired mixing and foaming properties for foam extrusion.