Enhancing Unit Value Realization of Hair Sheep Skin- an Assessment of Changes Between Butt and Belly Regions and its Value Addition Using Collagen Hydrolysate
Creators: name: Negasa, Dagnew
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2014

description: Skin will undergo changes in biochemical and biophysical properties during leather processing. Biochemical composition varies with respect to different regions of the skin like butt, belly, and neck. Supported with the nature of structure and chemical constituents of the skin, leather processing chemicals do have different propensity to different parts of the skin. Belly region's looseness and substance non-uniformity are the main problem in leather making from sheep skin (SS) particularly for shoe upper. Having a back with the leather processing practice and statistical data, an exuberant substance non-uniformity for sheep shoe upper is still recurrent in our country's context. To address same issue, this work focusses on the analysis of histology and biochemical properties of butt and belly portion of hair sheep skin besides the investigation of application collagen hydrolysate on the value addition of dyed crust leather and emission load during pre-tanning. Globular proteins are relatively higher in the butt region than the belly, whereas it is reverse in the case of fibrous proteins except collagen. Interestingly, the presence of proteoglycans content in butt regions is significantly high compared to belly and in case of fat it is reverse. Thus, the effect of liming and bating operations in removing unwanted skin constituents is stronger in butt and belly regions of SS, respectively, which reflects the requisite importance of the two unit operations in the pre-tanning operations. ASC contribution is higher in butt region than belly and the reverse is true in the case of PSC. The overall collagen content is considerably higher in butt than belly which may be the major cause of the higher strength characteristics of butt regions. Cr2O3 content is high in butt region than belly which corroborates with protein content and its interaction with tanning agents. Distribution of pore size influences the breathability property of leather which has been seen to vary in all the unit operations. Scanning electron microscope study complements same trend with respect to changes in the cross-section of the skin during leather processing. Therefore, the considerable variations observed among the two regions of SS would help the tanners and chemical manufactures to have more information on the parts of skins so as to improve the cutting value of the thin part of skin. Collagen hydrolysate being prepared under thermal alkaline condition enhances the hide substance of both belly and butt regions of sheep skin during pre-tanning when offered at pH 9.0. Despite the fact that Cr2O3 uptake found to be reduced in same way the CH uptake increased in both regions of SS, the Ts still found to be greater than 90oC thereby strengthening xv the application of CH in leather processing. In addition to the pore size distribution of the regions of SS, it has been observed that the fibre density of skin matrix also plays its own part for the uptake and retainment of treatment chemicals. The higher increase in the protein content of butt part of SS than belly augments same. The dyestuff exhaustion is by far better for CH treated leather than commercial protein fillers (CPF) used during the study. The increased in the dye exhaustion and overall physico-chemical properties of CH treated upper leathers would highly help the competitiveness of the tanner for the use of CH particularly coined as wealth from waste. The use of CH would be convenient for the value addition of lower end products. The emission load of tanning process liquor with CH is higher than conventional one and same is true for post-tanning process liquor with CPF.