Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: NEW AND EFFICIENT PROCESSES FOR MAKING QUALITY LEATHER
2008 Annual Report


1a.Objectives (from AD-416)
Develop new technology for preparing hides for tanning. Establish drying and finishing processes and develop in-line nondestructive tests for improving the quality and durability of leather. Hide Preparation: The additional funding will be used to expand the scope of hide preparation research by investigating ways to impart efficiencies to short-term hide preservation (brine-curing).


1b.Approach (from AD-416)
Oxidative chemicals will be evaluated for dehairing activity. Following dehairing, fleshing and splitting, the grain split will be further dehaired if necessary to remove remaining hair stubble. Further processing would complete the conversion of hide to crust leather. Enzymes (keratinases, dispase, acidic or alkaline proteases, and type IV collagenases will be evaluated as alternatives to chemical dehairing. Processes will be developed for partial or total removal, from limed hides, of proteoglycans (such as decorin) and glycans (such as dermatan sulfate) by first 'opening-up' the hides thoroughly to the entrance of chemicals and then treating the hides in the presence of concentrated salts with chymotrypsin, trypsin, pancreatic bate, halophile protease and/or glycanases (during bating). Both the decorin core-protein and the sulfated glycan content will be measured before and after application of the novel treatment, and mechanical and physical changes in the resultant leather will be evaluated. The effect of treatments on the physical and mechanical properties of leather ultimately made from the treated hides will be assessed. A mathematical, predictive drying model for chrome-free leather will be established and compared to the earlier one developed for chrome-tanned leather. Based on the new model, the optimal drying conditions for chrome-free leather will be identified. A finishing process will be developed that will improve the UV- and heat resistance of automobile upholstery leather. Alpha-tocopherol (Vitamin E) will be added during wet processing or added to the finishes and applied to the grain layer of the leather during the finishing process. In-line nondestructive testing technology by acoustic emission (AE) will be developed to assess the mechanical properties of leather following drying, staking, buffing, drum milling, and finishing. The additional funding will be used to evaluate processes for expediting the diffusion of salt into the hide. The ability of acoustic/mechanical energy or alternative salt formulations to shorten the time of brining and possibly decrease the salt requirement will be assessed.


3.Progress Report
Scientists developed alternatives to sodium sulfide to dehair hides in the tannery. A CRADA has been negotiated with a tannery to scale up the ERRC oxidative unhairing process (based on alkaline percarbonate). Studies on low float oxidative formulations have been completed; analysis of the oxidative dehairing waste stream is on going. (NP306: Comp. 1, Quality Characterization, Preservation, Enhancement; Pbm. Area c, Factors and Processes that Affect Quality; and Comp. 2, New Processes, New Uses, and Value-Added Foods & Biobased Products; Pbm. Area c, New and Improved processes and Feedstocks).

Developed a one dimensional diffusion model to explain the uptake of salt by a hide during brine curing. The next step is to determine the effects of surfactants on the uptake of salt. The ultimate goal of this research is to determine if it is possible to reduce the time needed to brine cure a hide. (NP306: Comp. 1, Quality Characterization, Preservation, Enhancement; Pbm. Area c, Factors and Processes that Affect Quality; and Comp. 2, New Processes, New Uses, and Value-Added Foods & Biobased Products; Pbm. Area c, New and Improved processes and Feedstocks).

Decorin is a minor but persistent component in hides that remains as the hides are tanned into leather. CWU scientists hypothesized that further removal of decorin would lead to softer leather. Techniques for decorin analysis were refined to eliminate inconsistencies in the results; modified SDS-PAGE and Western blotting were added to the prior-applied ELISA technique for greater specificity and sensitivity. The improved techniques for decorin analysis will enable studies to correlate decorin content with leather softness. (NP306; Comp. 1, Quality Characterization, Preservation, Enhancement; Pbm. Area b, Methods to Evaluate and Predict Quality, and c, Factors and Processes that Affect Quality)

Developed an analytical technique to establish a generated baseline of available decorin in pieces of whole hides (not powdered) and followed available decorin content as the hide is going through the tanning process to leather after applying the techniques developed above. They observed that different sections of raw bovine hide have varying amounts of initial decorin content. However, after subjecting all the hide sections to the same tanning treatments, the amount of available decorin remaining in each leather sample has no significant difference. (NP306; Comp. 1, Quality Characterization, Preservation, Enhancement; Pbm. Area b, Methods to Evaluate and Predict Quality, and c, Factors and Processes that Affect Quality)

Designed a composite drying frame that facilitates the composite drying (toggling plus vacuum drying) experiments with a biaxial stretch to increase area yield. Carried out drying experiments to combine toggling and vacuum drying together. Investigated how toggling % affects the mechanical properties of chrome-free leather tanned with glutaraldehyde. (NP306:Comp. 1, Quality Characterization, Preservation, Enhancement; Pbm. Area c, Factors and Processes that Affect Quality)


4.Accomplishments
1. Novel complimentary analytical techniques for the detection of various proteins in hides: Previously there was no complimentary analytical method to quantify the minority proteins such as decorin, which is composed of protein and sugar and is believed to govern the softness of leather. ARS scientists recently established a more reliable analytical technique combining gel electrophoresis, antibody tests specific for decorin and mass spectrometry, which verified that the compound determined by colorimetric technique is indeed decorin and made possible the identification of other proteins that also underwent changes during tanning. With the availability of more diversified analytical techniques, the scientists can find the true optimum amount of decorin allowed to remain in leather to account for its soft, flexible, and yet strong physical characteristics (NP306; Comp. 1, Quality Characterization, Preservation, Enhancement; Pbm. Area b, Methods to Evaluate and Predict Quality, and c, Factors and Processes that Affect Quality)

2. Developed optimal dehairing processes: Traditionally sulfide is used to dehair bovine hides; however sulfide poses both a health hazard and an environmental hazard. Tanners have expressed an interest in eliminating sulfide from the tannery. ARS scientists have developed a dehairing process based on alkaline sodium percarbonate (a white crystalline water-soluble chemical composed of sodium carbonate and hydrogen peroxide), which eliminates the use of sulfide from the tannery and eliminates sulfide from the waste stream. ARS is carrying out this research under a CRADA with a major domestic tannery and demonstrated that it is feasible to manufacture leather from oxidatively dehaired hides while concurrently reducing the amount of waste generated during the dehairing process. (NP306, Quality and Utilization of Agricultural Products; Action Plan Component 1, Quality Characterization, Preservation, and Enhancement; Pbm Area 1c, Factors and Processes that Affect Quality)

3. Established the optimum drying process for chrome-free leather: Because of environmental and health concerns over the use and disposal of chrome-tanned leather, chrome-free leather has gradually gained commercial importance. The quality of chrome-free leather, however, is known to be inferior to that of chrome-tanned leather. ARS scientists developed a novel drying method that applies both vacuum and biaxial “toggling” (a leather industry term indicating the action of stretching leather by using toggles) simultaneously to improve the quality of chrome-free leather. This method offers faster speed and lower temperature drying, which is particularly suitable to heat-vulnerable chrome-free leathers. The established optimal drying condition achieved a 16% increase in area yield with good leather quality, which tanneries may use to improve the quality of chrome-free leather and enhance profits. (NP306, Quality and Utilization of Agricultural Products; Action Plan Component 1, Quality Characterization, Preservation, and Enhancement; Pbm Area 1c, Factors and Processes that Affect Quality).


5.Significant Activities that Support Special Target Populations
None.


6.Technology Transfer

Number of New CRADAS1
Number of Active CRADAs1
Number of Non-Peer Reviewed Presentations and Proceedings1
Number of Newspaper Articles and Other Presentations for Non-Science Audiences1

Review Publications
Mozersky, S.M., Latona, R.J., Marmer, W.N. 2007. Removal of Available Decorin Core-Protein from Powdered Bovine Hide by Treatments used to Process Intact Hides into Leather. Journal of American Leather Chemists Association. 102(7):222-226.

Ramos, M., Latona, R.J., Marmer, W.N. 2007. Monitoring of Available Decorin in Different Parts of Bovine Hide during its Processing into Leather. Journal of American Leather Chemists Association. 102(12):404-407.

Hernandez Balada, E., Marmer, W.N., Kolomaznik, K., Cooke, P.H., Dudley, R.L. 2008. Mathematical Model of Raw Hide Curing with Brine. Journal of American Leather Chemists Association. 103(5):167-173.

Liu, C., Godinez-Azcuaga, V.F., Latona, N.P., Hanson, M., Finlayson, R.D. 2008. New Acoustic Methods for Nondestructive Evaluation of Leather Quality. Journal of American Leather Chemists Association. 103(3):89-127.

Liu, C., Latona, N.P., Dimaio, G.L., Cooke, P.H. 2008. Polymeric Coatings Containing Antioxidants to Improve UV and Heat Resistance of Chrome-Free Leather. Journal of American Leather Chemists Association. 103(6):167-175.

Liu, C., Godinez-Azcuaga, V.F., Latona, N.P., Hanson, M., Ozevin, D. 2008. Airborne Ultrasonics for Nondestructive Evaluation of Leather Quality. Journal of American Leather Chemists Association. 103(7):209:214.

Last Modified: 4/15/2014
Footer Content Back to Top of Page