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Research Project: Improving the Quality of Animal Hides, Reducing Environmental Impacts of Hide Production, and Developing Value-Added Products from Wool


2018 Annual Report

1: Enable new commercial methods to reduce or eliminate manure contamination of hides prior to hide removal, and one or more process models will be developed to estimate the expected costs for new technologies so enabled. 2: Enable new commercial methods for curing hides and skins and that reduce salt usage, and one or more models will be developed to estimate the expected costs for new technologies so enabled. 3: Enable new commercial methods to characterize hide quality in the raw state, and one or more models will be developed to estimate the expected costs for new technologies so enabled. 4: Enable new commercial products from Keratin extracted from wool.

The cleaning of bovine hides to remove manure balls and other organic contaminants will be enhanced by incorporating a combination of enzymes, glycerol, and sanitizing agents into the traditional cleansing solution ingredients. The efficiency of manure cleansing will be assessed by monitoring the bacterial count before and after the hide washings. Low salt hide preservation will be developed by using the combination of dehydrating agent, biocide, glycerol, and sanitizing agents with a fraction of the amount of salt used in traditional hide preservation. For improved efficiency and extended bovine hide preservation, the addition of various polyethylene glycol (PEG) fractions will be evaluated with the treatments of glycerol, biocides, and sanitizing agents. Nondestructive evaluation technology will be developed for the characterization of hide quality by incorporating airborne ultrasonic (AU) technology. The through transmission mode will be applied so that more useful information can be extracted from the AU scan, particularly for hides, which are covered by hair. The amplitudes of the transmitted airborne signals at every point on the hide surface were measured, color-coded, and mapped into an image file for each hide or leather. The correlation between AU data and physical properties of hides will be examined and statistical software will be used to establish the regression equation that enables one to predict the quality of hides using AU testing. Keratin will be extracted from coarse, low grade, unmarketable wool, by environmentally benign and economical methods, functionally modified by chemo-enzymatic methods, and applied to domestic wool, yarn, or fabric, to improve its properties. Conditions for chemical and enzymatic modification of wool will be optimized at the bench scale first, then scaled up. Intact wool will be modified chemo-enzymatically to add functional groups or functionalized keratin, and evaluated for improved properties, such as softness, comfort, resistance to shrinkage or improved water repellency. Promising research begun under a previous project, that demonstrated the ability of transglutaminase to catalyze the attachment of O-phosphorylethanolamine, potentially a flame retardant, to keratin and other proteins will be adapted for the surface derivatization of wool fabric, with the aim of imparting flame resistance. Economic assessment will be performed for all objectives every 12 months to evaluate the progress toward targets with adjustment along the way as necessary. After the process model is developed with equipment sizing and unit operations, capital and operating costs are then estimated using cost analysis software.

Progress Report
Progress was made on all objectives, all of which fall under NP 306 – Quality and Utilization of Agricultural Products, Component 2, Non-Food, Problem Statement 2A: Maintain/increase/enhance non-food product (fiber including hides) quality by developing new or improved postharvest technologies/process efficiencies and reducing processing risk. For Objective 1, project scientists tested the effectiveness of spray washing hides with previously developed decontamination formulations containing various concentrations of halamine and cinnamaldehyde, two food industry antimicrobials. Spray washing with these formulations substantially reduced the bacterial contamination, including pathogens such as Enterobacteriaceae, Salmonella and Escherichia coli, from the haired surface of bovine hide in a short period of time (1 to 5 minutes). Bacterial contamination on the outer grained hide of cattle serves as a significant challenge to the meat industry and food safety. Survival of such harbored bacteria can facilitate cross-contamination of the underlying meat and meat processing equipment in the slaughter house and cleaning with only water has been shown to have minimal effect on bacterial populations. A large-scale experiment using a full size bovine hide was also performed to validate the effectiveness of the halamine containing formulation. The formulations were also evaluated for their effects on leather produced from the treated hides, no detrimental impact on leathers was observed. A small increase in production cost will be added due to the implementation of a new process in the meat packing plant, however, it could be eventually reduced by lower losses due to contaminated meat. An industry partner has been identified and is in the process of establishing collaboration agreement. For Objective 2, project scientists previously developed an antiseptic-based bovine hide preserving formulation that uses only 45% saturated brine solution, a 50% reduction in salt usage compared to traditional curing methods. The developed process has been found more effective in limiting microbial growth on cured hide, for more than 30 days, than the conventional method of preserving the bovine hides. In FY 2018, the efficacy of this previously developed alternative hide curing system was assessed by monitoring the environmental impacts of leather processing effluents. Methods for monitoring total dissolved solid (TDS), chloride content (Cl-), total solids (TS), total aerobic bacterial counts in soaking liquor, bio-chemical oxygen demand (BOD) and chemical oxygen demand (COD) were optimized for use with leather processing effluents. The environmental advantages of the alternative hide curing method are demonstrated particularly by 50% reductions in TDS and chloride content in leather processing discharge when compared to traditional methods of bovine hide preservation. Sustainability, including the ability to produce quality of leather, was assessed through post-tanning analysis of the surface properties (grain pattern, SEM images), mechanical properties, and organoleptic evaluation. Project scientists were also successful in further reducing salt usage for bovine hide preservation to 35% saturated brine solution by combining it with a bactericide/fungicide. In this study, research results and cost analysis suggest that the developed hide preservation technique has the potential to be a viable alternative for traditional high salt-based curing. We have made progress in the development of polygenipin as new crosslinkers for collagen. The development of high quality chrome-free leather and the utilization of proteinaceous byproducts of tanning have long been challenges for the leather industry. In a collaborative research, a foreign visiting scientist and ARS scientists in Wyndmoor, Pennsylvania have demonstrated that polygenipin can crosslink collagen, in powdered hide. Thermogravimetric analysis showed that long-range intermolecular crosslink bridges formed between collagen molecules result in more thermally stable hide powders. In addition, different degrees of genipin polymerization imparted blue or brown colors to the crosslinked product without the need for dyes. Moreover, by varying the polymerizing conditions, both the thermal stability and the color of the crosslinked product can be varied. Thus, polygenipin crosslinked collagen may potentially have a role in the development of chrome-free tannages as well as biomedical and packaging applications. For Objective 3, project scientists are using a statistical experimental design to establish a mathematical model that expresses the relationship between hides/leather quality and airborne ultrasonic (AU) physical quantity. Project scientists also investigated the effects of ultrasonic wave frequency and scanning speed on the test results, thereby optimizing the nondestructive AU evaluation method for animal hides. Lower frequency sensors, 50 kHz, showed the best results in the study which allowed better penetration of the waves through the attenuating hides with hair on. Hides were scanned with a three-dimensional scanner and samples were mounted vertically to better represent production processes. An algorithm was developed for performing the AU test for the quantification of hide quality. The recent economic analysis indicated the new AU testing system to be comparable to the current manual grading system. For Objective 4, project scientists prepared swatches cut from commercially obtained worsted wool and wool jersey fabrics that were cleaned by extraction with hexane to remove residual and/or processing lipids. The clean swatches were then treated with microbial transglutaminase (TG), an enzyme widely used in the food industry, that catalyzes the formation of crosslinks between protein bound glutamine residues and free amino groups in proteins or other molecules. In addition to the fabric and TG, (with maltodextrose or gelatin as a carrier) treatment mixtures included various combinations of 4-aminobenzoic acid (PABA) containing a free amino group, as a UV-protectant, soluble keratin, or soluble keratin previously modified with PABA. Results were evaluated by fluorescence after thorough washing to remove unbound reagents. Factors considered for the economic evaluation were the relative costs of chemical or enzymatic derivatization, including energy input and safety factors.

1. Novel methods for reducing manure contamination of cattle hides. Pathogenic cross-contamination from haired surface of cattle to underlying meat during processing is a major challenge for meat packing industries and poses a threat to public safety. ARS researchers at Wyndmoor, Pennsylvania have developed aqueous based spray solution which can remove manure/mud balls attached to haired surface in 5-8 minutes and at the same time decontaminate the carcass prior to slaughter. The developed methods which have shown to effectively reduce bacterial contamination from the haired surface of cattle hides including pathogens such as Salmonella and Escherichia coli offer the deep cleaning prior to harvesting cattle to produce safe meat. Furthermore, the damage to hides (due to the presence of manure/mud balls) is reduced, thus facilitating the production of high quality leather.

2. Preservation of hides using a combination of antiseptic and bactericide. ARS researchers at Wyndmoor, Pennsylvania have developed techniques to preserve bovine hides for more than 30 days, in which 35%- 45% saturated brine solutions are used in combination with low concentration of antiseptic and bactericide. This new preservation method cuts salt usage by more than 50% from the traditional method of hide curing where 95% saturated brine solution is used. Research results showed that the new formulations preserve hides through better control of microbial growth on hide surface throughout the storage time and produce the leather which is comparable in quality to that made from traditionally cured hides. Using less salt reduces overall pollution from tannery waste significantly.

Review Publications
Liu, J., Liu, C., Brown, E.M. 2017. Development and characterization of genipin cross-linked gelatin based composites incorporated with vegetable-tanned collagen fiber (vcf). Journal of American Leather Chemists Association. 112(12):410-419.
Taylor, M.M., Bumanlag, L.P., Latona, N.P., Brown, E.M., Liu, C. 2017. Preparation and characterization of gelatin/chitosan/carbodiimide films. Journal of American Leather Chemists Association. 112(12):428-435.
Liu, J., Liu, C., Brown, E.M., Keyong, T. 2018. Characterization and thermal properties of polygenipin-crosslinked hide powders. Journal of American Leather Chemists Association. 113(4):96-104.
Long III, W., Sarker, M.I., Marsico, R.M., Latona, N.P., Ulbrich, L.M., Muir, Z.E., Liu, C. 2018. Efficacy of Citrilow® and Cecure® spray wash on the prevalence of aerobic and enterobacteriaceae/gram negative enteric bacilli and cattle hide quality. Journal of Food Safety.
Long III, W., Sarker, M.I., Liu, C. 2018. Evaluation of novel pre-slaughter cattle wash formulations for meat and byproduct safety and quality. Journal of Food Science and Technology. 14(2):33-41. https://doi:10.19026/ajfst.14.5829.
Sarker, M.I., Long III, W., Liu, C. 2018. Preservation of bovine hide using less salt with low concentration of antiseptic, part I: effectiveness of developed formulations. Journal of American Leather Chemists Association. 113(1):12-18.