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Video

Protein and Co-Products

Session:: Protein-based Materials and Hydrocolloids for Food and Non-food Applications

Relations between soy protein aggregation state and adhesive performance

Wednesday, May 3, 2023
12:00 PM – 12:20 PM MDT
Room: 207
Abstract: Interest in replacing some of the ~15 million tons/yr of urea-formaldehyde (UF) adhesives in interior wood products with bio-based alternatives continues to grow because of a desired bio-based, circular economy, new European regulation on melamine (used to meet formaldehyde emission targets with UF), and lower allowed formaldehyde emissions.

Typical soy adhesive preparations do not fully utilize protein’s adhesive potential, as evidenced by the ~2-3x increase in wet strength that results from jet cooking soy protein. Unlike many methods of improving soy adhesive strength, jet cooking is still highly effective even when crosslinking agents are added.

In this study we investigated the impact of soy formulation on wet adhesive properties (nanoindentation hardness and elastic modulus, mixed mode crack propagation energy, network structure via SEM), as well as plywood performance - wet shear (ASTM D906) and 3 cycle soak (ANSI/HPVA HP-1).

Soy adhesives overwhelmingly fail cohesively when tested wet, indicating that interactions between soy components are the weak link needing improvement. Under typical plywood production conditions, there was little to no performance benefit from removing carbohydrate from the soy adhesive. The jet cooking method of denaturing soy protein, on the other hand, dramatically improved bond strength. This leads us to believe that the aggregation state of the protein is far more important to adhesive performance than is carbohydrate interference. Supporting evidence is provided by the fact that ovalbumin, which undergoes a hydrophilic-hydrophobic conversion upon heating, is an excellent wood adhesive. The role of protein-protein interactions, and potentially helpful protein aggregation conformations in adhesives, will be discussed.