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Volume: 109      Number: 5     Page: 161-170     Year: 2014
Ethiopian tanners face a shortage of raw material input for the production of leather. The government strategically planned for importing raw skins from neighboring countries and also for effective utilization of available raw material resources in the country. The meat of Wanke sheep is in high demand in international markets, but the skin commands low price not only due to low availability but also less demand by tanners due to natural problems associated with the skin. Hence, tanners treat the skin as a reject. The problems of Wanke skin include high natural fat deposition, thin substance and low strength. Usually, leathers made out of Wanke skins have low selections compared to Ethiopian sheep skins and are mainly utilized for making lining leather. In this work, efforts have been made to develop a process technology for making high value leathers with improved properties from Wanke sheepskin.
Volume: 109      Number: 5     Page: 151-160     Year: 2014
The effect of nutrient composition of tannery wastewater on aerobic biological treatment, particularly on the removal of ammonia nitrogen (NH3-N) and total nitrogen (TN) was investigated based on the theory of nutrient balance. During the biological treatment of conventional tannery wastewater, total organic carbon (TOC) and total phosphorus (TP) were almost exhausted. However, the removal of TN was unsatisfactory, suggesting that tannery wastewater contains excessive N source and insufficient C and P sources. When extra C and P sources were added together into the wastewater, the removals of NH3-N and TN increased significantly. Under the optimal ratio of TOC:TN:TP (10:1:0.2), the removals of NH3-N and TN were 100% and 80%, respectively, and the added C and P sources were almost consumed by activated sludge. This means that a good nutrient balance was achieved in this condition. Accordingly, when ammonium salts are replaced by organic acids and phosphates in the deliming and bating processes, it is reasonable to assume that the change of wastewater composition would favor the aerobic biological treatment of wastewater.
Skin Characteristics of Cervus elaphus L. from Republic of Tuva in Russia 
by Urana Dandar, Selime Menteş Çolak, Remziye Deveci,
Volume: 109      Number: 5     Page: 141-150     Year: 2014
Characteristics of an animal raw skin are closely related to the physical properties of finished leather obtained from the skin. Although numerous studies have been performed on determination of physical properties of tanned deerskin, characteristics of raw deerskin have not yet been described in literature. In the present study, data on morphological, histochemical and chemical characteristics of wild red deer (Cervus elaphus L.) skins obtained from Republic of Tuva within the Russia Federation are presented and the relevant differences between skins of other animal species described. Table Top Scanning Electron Microscopy (TSEM) and Scanning Electron Microscopy (SEM) were used to determine the morphological characteristics of raw deerskins. For histochemical studies the cross section of skins were observed by Research Microscopy (RM). Hydroxyproline content, Total Kjeldahl Nitrogen (TKN), volatile matter, fat content, water-soluble-matter, sulphated total ash and fatty acid contents of raw deerskins were analyzed to further characterize the chemical composition of deerskin. Deerskin has comparatively higher TKN values, lower fat content with higher unsaturated fatty acid ratio, when compared to sheepskin. TSEM and SEM analysis showed that fur fibers and guard hairs of red deer skin were characterized by large cortex and medulla respectively that provides good isolation properties. In addition, high hydroxyproline content, low fat content, and tightly packed collagen fibers revealed by histochemical observations consolidates the long lasting property of deer skin. Assessment of skin characteristics enabled gathering data on physical and chemical properties of red deer skin, which is significant in choosing appropriate potential raw material that will produce the most suitable leather for a specific application.
by Jianzhong Ma, Xueyan Hou, Dangge Gao and Jing Zhang
Volume: 109      Number: 5     Page: 131-140     Year: 2014
Enzymes play an important role in the biological treatment of animal skin collagen in the leather making process. In this work, three proteases (2709, LimeG and SoakL) with different molecular weight were used in the treatment of cattle hide. Protein and hydroxyproline absorbance was measured to evaluate the treatment effectively. Proteases labeled by Fluorescein Isothiocyanate (FITC) were used to treat the cattle hide to observe the diffusion and reaction behavior of proteases in cattle hide matrix. The results indicate that when the cattle hide was treated with smaller molecular weight protease, the degradation degree of the protein and collagen was more than that of the cattle hide treated with larger molecular weight protease. The fluorescence microscopy images demonstrate that during the early stages, proteases chiefly diffused into the cattle hide matrix through pores and hair follicles, and then diffused into the inner layer via hair follicles to hydrolyze inter-fibrillary proteins for opening up collagen fibers. In the present investigation, a visible assessment for the diffusion and reaction behavior of proteases in the enzymatic treatment of cattle hide matrix was reported.
Development of Alginate-Chitosan Based Biopolymers for Leather Retanning 
by R. Aravindhan, K. Sreeram and J. Rao
Volume: 109      Number: 4     Page: 99-109     Year: 2014
Hides and skins when received in tanneries have closely and firmly packed together bundles of collagen fibers, with elastin and other non-fibrous proteins aiding a dense structure formation. However, in order to ensure the easy diffusion of chemicals, a series of pre-tanning operations ensure the opening up of the fiber bundles and the removal of the non-fibrous materials, resulting in a loose structure. A majority of leather consumers often demand properties, which were available on hides and skins, but lost during the pre-tanning operations. One such property is the compaction or firm packing of fiber bundles. While vegetable tanning processes provide for good fullness and firm packing of fiber bundles, the lack of strength and stability against wet heat forces the tanners to adopt chrome tanning. Chrome tanning provides for good inter and intra networking of fibers, but is unable to replenish the firmness found in the original raw material. To overcome this drawback, tanners often resort to the use of a combination of retanning agents in varying proportions. The varying character of these products results in non-uniform and poorer uptake. In this work an attempt has been made to develop syntans from biopolymers such as chitosan and alginate, which could provide fiber compaction to the leather.
The Role of Neutral Salt for the Hydrolysis and Hierarchical Structure of Hide Fiber in Pickling 
by Haiming Cheng, Min Chen and Zhiqiang Li
Volume: 109      Number: 4     Page: 125-130     Year: 2014
Pickling process carried out for adjusting the skin to the desired pH for tanning, in which neutral salts were added to avoid skin fiber from the acid swelling. This research study aimed at investigating the contribution of neutral salt to the hydrolysis and the fibrous structure of collagen fiber in acid solutions. Collagen fiber and bovine hide in sulfuric acid solutions with sodium chloride or sodium sulfate were investigated. The total protein concentration in the solutions was determined. The hierarchical structures of bovine hide in different acid and neutral salt systems were investigated by optical microscope, TEM and SEM. This study suggested the importance of neutral salt for the hydrolysis and the dispersion of collagen fiber in pickling. It implied that the osmotic swelling by acid could not reach the inner scale of fibril. The decrease in mechanical properties for the leather tanned with salt free pickling may have been caused by osmotic swelling destroyed the interactions among the fibril and fiber bundles.
New Challenges in Chrome-free Leathers: Development of Wet-bright Process 
by A. Bacardit, S. Van der Burgh, J. Armengol and L. Olle
Volume: 109      Number: 4     Page: 117-124     Year: 2014
The aim of the present work was to develop a new tanning process (wet-bright) that produces perfectly white leather meeting all of the requirements for many kinds of articles, such as automotive, garment and shoe upper. This new process gives leather that is free of chromium, aldehydes, aldehyde precursors and organic solvents. It is the application of a new system based on a product designated Tanfor TTM from the manufacturer Kemira. When compared to existing traditional wet leather processes, there are economic and environmental advantages resulting from the use of this new system. Also, the mineral character of the new product system offers leathers with high dye affinity; thus enabling very bright colors in all leather applications. We believe this leather offers such perfect dyeing properties because of the brilliant whiteness of the wet-bright intermediate substrate.
Sustainability in Process Innovation: Development of a Green Tanning Process Supported by LCA Methodology 
by M. Puccini, M. Seggiani, D. Castiello and S. Vitolo
Volume: 109      Number: 4     Page: 110-116     Year: 2014
As a response to the growing concerns about a variety of environmental issues expressed by public opinion and political bodies, the leather industry needs to support its market by environmental criteria as a guarantee of quality. For this reason, assessment tools as Life Cycle Assessment (LCA) methodology, which allow a more thorough knowledge of the products to the enterprises and can help to guide the environmental policies, are recommended (e.g. EC Directive on Ecologic Labels). The LCA methodology, described in details by the ISO 14000 series, allows the assessment of the environmental impacts due to products, processes, or services, by the identification of the inputs (e.g. energy and material consumption) and outputs (e.g. waste and pollutant production) streams exchanged by the process with the environment (i.e. from raw materials procurement to waste streams disposal). The application of LCA as tool for integration of sustainability aspects in process design and development is gaining wider acceptance and methodological development. In this study, the life cycle modeling was used to support the development of a novel tanning process based on the use of a new class of tanning agent produced from renewable resources (e.g. glucose). The experimental activity performed to investigate the technical feasibility of the innovative tanning cycle was supported by the modelling of the process using the LCA methodology in order to assess the environmental performance of the leather production cycle. Therefore, an LCA analysis was performed in order to compare the glucose-tannage process with the traditional one from an environmental point of view.
Improvements in Leather Surface Hydrophobicity through Low-pressure Cold Plasma Polymerization 
by Ya-e Feng, Xuepin Liao, Yanan Wang and Bi Shi
Volume: 109      Number: 3     Page: 89-95     Year: 2014
Vinyltriethoxysilane (VTES) was polymerized and deposited on the surface of upholstery crust leather by using low-pressure cold plasma technology. After plasma treatment (50 W, 300 s), the initial water contact angle of the leather surface increased from 120o to 140o, showing a significantly improved hydrophobicity of leather surface. The increased hydrophobicity of leather surface could remained even the leathers were stored for 240 d. The surface morphologies of leather were characterized by Scanning Probe Microscope (SPM) and Scanning Electron Microscope (SEM). Unlike the fiber-like texture of untreated leather, a coating of VTES polymer on the plasma treated leather surface was observed by SPM. SEM and SPM images indicated that this coating film was on the surface of collagen fibers rather than the whole surface of leather, which would not reduce permeability of air and water vapor of the leather. Energy Dispersive X-ray Spectroscopy (EDS) was performed to determine the chemical composition of leather surface. The contents of Si and O increased remarkably as leather surface was covered with polymerized VTES. The X-ray Photoelectron Spectroscopy (XPS) showed that the peaks attributed to C=C bonds of VTES and C=O bonds of collagen disappeared after plasma polymerization. All these results demonstrated that VTES was polymerized and deposited on the surface of collagen fibers after plasma treatment, which resulted in a hydrophobic surface of leather.
Biopolymers Produced from Gelatin and Whey Protein Concentrate Using Polyphenols 
by M. Taylor, J. Lee, L. Bumanlag, R. Latona and E. Brown
Volume: 109      Number: 3     Page: 82-88     Year: 2014
Several researchers have recently demonstrated the feasibility of producing biopolymers from the reaction of polyphenols with gelatin in combination with other proteins (e.g. whey) or with carbohydrates (e.g. chitosan and pectin). These combinations would take advantage of the unique properties of both species and at the same time create products with enhanced functional properties. We have successfully demonstrated that the polyphenolic gallic acid and the vegetable tannins quebracho and tara could be used to modify gelatin and whey protein concentrate (WPC) resulting in a subsequent change in the physicochemical properties of each. When gelatin-polyphenol products were used as fillers, considerable improvements were seen in the subjective properties of the leather and when compared to control samples, there was no significant impact on mechanical properties. In this continuing research, we have begun to evaluate the potential of tara-modified gelatin/WPC biopolymers, specifically for their application as fillers. In this study, modification parameters for gelatin/WPC combinations will be explored, and the results of product characterization using physicochemical analyses will be presented. These studies could further contribute the use of sustainable resources in production of unique products that may have leather processing applications.