Enhancing Unit Value Realization of Hair Sheep Skin- an Assessment of Changes Between Butt and Belly Regions and its Value Addition Using Collagen Hydrolysate
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Date
2014-09
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Addis Ababa University
Abstract
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
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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.
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Keywords
Bio- Engineering under Leather Stream