Protein structures dictate their adhesive performance

Abstract

Proteins were useful as adhesives for wood bonding, including those derived from animals (collagen, casein, ovalbumin, and blood), and plants (soy, canola, and cottonseed). These proteins have different structures that dictate their wood adhesive performance. Hydrolyzed collagens from animal hides and bones are hot-melt adhesives suitable for paper applications with durability improved by crosslinking. Soy flour adhesives, even with a crosslinker, are amphiphilic, giving moderate wet-strength wood bonds, while with ovalbumin (egg whites) curing exposes hydrophobic surfaces leading to high bond strength, both wet and dry. The presence of carbohydrates in soy flour contributes to lower wet bond strength but oxidizing these carbohydrates to reactive aldehydes leads to greatly improved wet bond strength. Adhesive research has concentrated on expensive commercial soy protein isolates which provide greater wet bond strength, due to jet cooking, compared to affordable soy flour. We propose this strength is primarily due to an increase in the size of the pre-gel protein structures. While soy adhesive literature generally describes soy proteins as elongated, spaghetti-shaped molecules, the model of a hydrocolloidal gel formed from sticky rice-like globular proteins as described in the food and general protein literature is more consistent with the properties of soy adhesives.

Citation

Frihart, Charles R.; Lorenz, Linda. 2026. Protein structures dictate their adhesive performance. Wood Material Science & Engineering. 21(2): 1247-1256. https://doi.org/10.1080/17480272.2025.2507146.