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Title: Use of high molecular weight biopolymers to improve the properties of chrome-free leather

Author
item Taylor, Maryann
item Lee, Joseph - Joe
item Bumanlag, Lorelie
item Brown, Eleanor - Ellie
item HERNANDEZ BALADA, EDUARD - University Of Barcelona

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2011
Publication Date: 12/1/2011
Citation: Taylor, M.M., Lee, J., Bumanlag, L.P., Brown, E.M., Hernandez Balada, E. 2011. Use of high molecular weight biopolymers to improve the properties of chrome-free leather. Journal of American Leather Chemists Association. 106(12):353-359.

Interpretive Summary: Chrome-free leather, which is increasingly replacing the more traditional chrome-tanned leather, has a tendency to being flat, empty, or weak and the grain sometimes has an inferior appearance to that seen in chrome-tanned hides. It has been shown that these chrome-free leathers require more filling than normal conventional chrome-tanned leather and large amounts of resins and polymers are commonly used to improve appearance. 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). Recently, we applied the modified fillers to chrome-free leather, and found that the strength of the treated leather was not significantly different from controls, but there was an improvement in the subjective properties (such as fullness). In this present study, we attempted not only to further improve subjective properties of chrome-free leather, but also to use a more economical whey protein concentrate (WPC)/gelatin combination. High molecular weight products were prepared from enzymatically-modified WPC/gelatin, whose properties could be described as having high viscosities and melting points. These products were applied to chrome-free leather and subjective properties, in particular fullness, break, and overall evaluation, were better than seen previously; there were no significant differences in the mechanical properties. Thus, by utilization of higher molecular weight WPC/gelatin products on chrome-free leather, we have made treatments that are more economical resulting in a subsequent improvement in leather quality.

Technical Abstract: In prior studies, we addressed the problems of poor leather quality, specifically “spring break” hides, by utilizing fillers produced from enzymatically-modified waste proteins, in particular those proteins from the leather and dairy industry (low quality gelatins and caseins or whey). In a more recent study, we applied low molecular weight enzymatically-modified gelatin/whey protein isolate (WPI) fillers to chrome-free or “wet white” leather. The leather was subsequently evaluated and it was found, as seen in previous studies, the mechanical properties of the treated leather were not significantly different from controls, but there was an improvement in the subjective properties, specifically in fullness. In this present study, we attempted not only to further improve subjective properties of chrome-free leather, but also to use a more economical whey protein concentrate (WPC)/gelatin combination as well as substituting sodium bisulfite (NaHSO3) for the more expensive dithiothreitol (DTT), which is used to denature whey prior to enzyme modification. High molecular weight products were prepared from enzymatically-modified WPC/gelatin, whose properties could be described as having high viscosities and melting points and whose SDS-PAGE gels showed that the WPC and gelatin had been extensively modified. These products were applied to chrome-free leather and subjective properties, in particular fullness, break, and overall evaluation, were better than seen previously. Furthermore, when NaHSO3 was substituted for dithiothreitol (DTT), products with a reproducible range of physical properties could be realized. Thus, by utilization of higher molecular weight WPC/gelatin products on chrome-free leather, we have not only made treatments that are more economical with subsequent improvement in leather quality but we also enhanced product preparation by utilization of NaHSO3 to denature the whey protein.