Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/12/2008
Publication Date: 4/1/2009
Citation: Hernandez Balada, E., Taylor, M.M., Brown, E.M., Liu, C., Cot, J. 2009. Whey Protein Isolate: A Potential Filler for the Leather Industry. Journal of American Leather Chemists Association. 104(4):122-130. Interpretive Summary: Looseness and coarse grain break are two of the most common characteristics of low quality leather. Upgrading of this leather could potentially yield an increase in cutting area and therefore a better economic return. Typically, petroleum-based products are used to improve the final appearance and feel of the leather. However, the rising cost of these products encouraged the search for alternative sources, such as renewable waste proteins. In this study, we were able to significantly improve the quality of the leather by treating it with whey protein isolate (WPI), a byproduct of the cheese industry, and gelatin, a byproduct of the leather industry. Samples of leather treated with this proteinaceous blend were fuller and exhibited a tighter grain break than the control samples. The leather showed an important affinity towards the proteins used, taking up at least 80% of the offered amount, and the protein was not significantly removed during the wash. Furthermore, leather that was pretreated with an enzymatic solution prior to the treatment with the WPI-gelatin blend showed even more notable improvement on the grain break over the controls, especially in the belly area (an area which normally has the poorest quality). Noteworthy, we demonstrated that the described process could be effectively applied to both upholstery and shoe upper leather. Thus, we have shown not only the potential of making fillers for leather from these renewable resources, but also have added value to not only to these waste proteins but also to the leather.
Technical Abstract: The upgrading of leather that presents loose areas and poor grain break is one of the most value adding opportunities for a tanner. Typically, petroleum-based products are used to improve the final appearance and feel of crust leather. In this study, we demonstrate that blends composed of whey protein isolate (WPI), a byproduct of the cheese industry, and small amounts of gelatin, a byproduct of the leather industry, could be effectively used as filling agents for both shoe upper and upholstery leather. Wet blue leather from three different areas in the hide (butt, belly and neck) was treated with the WPI-gelatin blend, retanned, colored and fatliquored, and their subjective and mechanical properties evaluated. The effect of pretreatment of the wet blue samples with various concentrations of the enzyme microbial transglutaminase (mTGase) was also examined. It was found that the rate of uptake of the WPI-gelatin blend by upholstery wet blue increased four-fold when it was pretreated with a 2.5% mTGase solution. Conversely, this rate was decreased when shoe upper was pretreated with increasing amounts of mTGase. The subjective properties (e.g. handle, fullness, color and grain break) of both shoe upper and upholstery leather that were treated with the WPI-gelatin blend were significantly improved over the controls. Importantly, the grain break of the belly area of samples that were pretreated with enzyme (both upholstery and shoe upper) was remarkably improved. Hence, fillers mainly composed by the less expensive WPI were demonstrated to be effective filling agents for both upholstery and shoe upper leather.