Preparation and characterization of polyphenol-modified gelatin products

Authors: Taylor, Maryann; Lee, Joseph - Joe; Bumanlag, Lorelie; Latona, Renee; Brown, Eleanor - Ellie; Liu, Cheng Kung

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2011
Publication Date: 2/1/2012
Citation: Taylor, M.M., Lee, J., Bumanlag, L.P., Latona, R.J., Brown, E.M., Liu, C. 2012. Preparation and characterization of polyphenol-modified gelatin products. Journal of American Leather Chemists Association. 107(2):51-59.

Interpretive Summary: In recent studies, we successfully addressed the problems of poor leather quality by utilizing fillers produced from enzymatically-modified waste proteins from sustainable resources, specifically proteins from the leather and dairy industry (such as low quality gelatins and caseins or whey). As we continue our research into use of sustainable resources, we are building on these and additional techniques to make products that could enhance finished leather. Vegetable tanning, utilizing the compounds extracted from plant materials, is used primarily for production of heavy leathers for saddles, belts and shoe soles. Recently, these compounds involved in vegetable tannage have been investigated extensively for their ability to modify gelatin. It has been reported that the resulting products could be used as films, encapsulating agents, and/or emulsions. We explored whether gelatin, when modified using these compounds, could give products with properties that might have application in leather processing. In our first study, we used quebracho, a commonly used vegetable tannin. It was demonstrated that gelatin could be modified, using quebracho, to make products that had increased melting points, high viscosities, and polymer-like behavior. We applied these products to hides as fillers and found that the resulting leather had superior subjective properties when compared to untreated control samples. Also the strength and other mechanical properties of the treated samples were not significantly different than control samples. Thus gelatin, a byproduct from the leather-making process, modified with quebracho, a commonly used sustainable tanning agent, could be utilized to improve crust leather products in the retanning, coloring and fatliquoring process.

Technical Abstract: We have demonstrated the effectiveness of enzymatic and chemical modification of waste protein from leather, used alone or in combination with protein from the dairy industry, in preparation of fillers for leather treatment. We are continuing to build on these techniques to make products from sustainable resources that can enhance retanned leather. Vegetable tanning, utilizing polyphenols extracted from plant materials, is used primarily for production of heavy leathers for saddles, belts and shoe soles. Recently, the polyphenolic acids involved in vegetable tannage have been investigated extensively for their ability to modify gelatin. We explored whether gelatin, when modified using polyphenols, could give products with properties that might have application in leather processing. In our initial studies, before we investigated individual polyphenolic acids, we tested tannins, e.g., quebracho, to see if indeed these vegetable tannins themselves could be used in crosslinking. These studies demonstrated that gelatin could be modified, using quebracho, to make products that had varying physical properties such as high melting points and viscosities and that the molecular weight determinations showed an extensive alteration in gelatin profile. These products were applied to blue stock as fillers and the resultant leather showed improved subjective properties and no significant differences in mechanical properties between treated and control samples. Thus a byproduct (gelatin) from leather-making process, modified with a common polyphenolic tanning agent (quebracho), can be employed to improve crust leather products in the retanning, coloring and fatliquoring process.