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United States Department of Agriculture

Agricultural Research Service

Title: Foaming Properties of Soy Proteins and Their Use in Plywood Adhesives

Authors
item Hojilla-Evangelista, Milagros
item Dunn, Jr, Larson - WILLIAMS BIOENGERY

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2001
Publication Date: N/A

Interpretive Summary: Foam extrusion is one method of applying glue to plywood. The glue is foamed with air to about six times its originial volume and then extruded in parallel strands (called "noodles") onto veneers that pass under the extrusion head. Glues for foam extrusion contain a protein extender, a material having adhesive properties that is added to the glue to reduce the amount of resin. Animal blood is the industry's current protein sourc in foamed glues, but concerns about animal blood's limited supply, health issues and storage stability have prompted the search for alternate protein extenders. This research was conducted to determine if soy proteins can replace animal blood in foamed glues. Foaming properties of glue mixes containing animal blood or various commercially-available soy products (meals, flours, concentrates, isolates) were compared. There were several soy products that matched the foam volume and foam stability that were produced by the blood-containing glue mix. The soy flours ISU-CCUR (Iowa State University-Center for Crops Utilization Research), Honeysoy 70, Honeysoy 90, Nutrisoy 7B and defatted Soyafluff, and the soy protein concentrates Arcon F, ISU-CCUR, Procon 2000 and Promine HV were identified as having the best potential to replace blood protein in foamed glue mixes. The development of soy-based foamed glues will not only produce a more environmentally-friendly plywood adhesive, but a cheaper one as well, if soy flours are used in the formulation.

Technical Abstract: No study has been reported on soy protein-based adhesives that are applied by foam extrusion, a relatively new technique that appears to have several advantages over other popular modes of glue application. Foamed plywood glues currently use animal-blood as their only extender. The main goal of this research was to determine if soy proteins could replace animal-blood protein in foamed glues. Foaming properties of glue mixes containing animal blood or soy protein products (meals, flours, concentrates, and isolates) were first compared and then correlated with molecular weights and surface hydrophobicity indices in an attempt to identify structure/ function relationships. The blood-based glue mix produced more foam than any of the soy-based glues. Soy flours and concentrates generally produced greater foam volumes and more stable foams than soybean meal and soy isolates. Differences in foaming properties could not be explained by solubility profiles or surface hydrophobicity indices. However, results of gel electrophoresis indicated that soy products with poor foaming properties had undergone extensive structure modifications during process- ing or contained considerably lesser amounts of protein available for foaming reactions. Foaming test results identified the soy flours ISU- CCUR, Honeysoy 70, Honeysoy 90, Nutrisoy 7B and defatted Soyafluff, and the soy protein concentrates Arcon F, ISU-CCUR, Procon 2000 and Promine HV as having the best potential to replace blood protein in foamed glue mixes.

Last Modified: 7/25/2014
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