Preparation of Sheepskin Unhairing Extracts from Locally Available Plants: Cleaner Leather Processing

Leather is made from animal hides and skins that have passed through several stages of processing, from soaking to nishing. Unhairing is a crucial processing stage in which hair is removed from the animal hide or skin through open up the hair and it facilitates subsequent operations. e conventional sodium sulde-based unhairing process generates a high volume of euent, which accounts for 50 to 70% of the total biochemical oxygen demand (BOD) and chemical oxygen demand (COD) load in the tanneries’ euent. is study aimed to investigate the potential of unhairing agents prepared from locally available plants. e research employed qualitative methods. Plant materials are collected, dried, and ground. In dierent proportions, unhairing extracts were obtained from Phytolacca dodecandra leaves, Cucurbita foetidissima fruits, and Solanum incanum fruits. In the conventional soaking process, plant extracts were applied in various concentrations to sheepskin. e physical parameters of conventionally processed (control) and experimentally treated leather were examined using FTIR, SEM, tear strength, percentage of elongation, and organoleptic tests. e unhairing solution was prepared from a mixture of 0.5% S. incanum extract, 0.5% P. dodecandra extract, 0.6% C. foetidissima extract, and 260 g/L lime powder lime, and this solution eectively removed the hair from the sheepskin in both hairs saving and hair burning unhairing process. e study revealed that the sheepskin treated with the plant extracts based on an unhairing agent and the conventional unhairing agent showed a comparable tensile strength (42.3 kg/ cm and 45.2 kg/cm), tear strength (140.1 kg/cm and 143.5 kg/cm), and percent elongation at break (40.2 and 42.3), respectively, which were above the permissible limit for leather production making. According to the study ndings, the plant extracts have a good potential for removing hair from sheepskin, and they are eco-friendly and cost-eective compared to unhairing chemicals such as sodium sulde.


Introduction
Tanning is the process of conversion of animal hides and skins into nished leather. In Leather processing, animal skins or hide are passed through di erent processing stages including the beam house, tanning, post-tanning, and nishing operations. Unhairing is a crucial operation in leather processing that involves removing the hair or wool from the hide or skin. e conventional chemicals being used during strength to hair and wools. Keratin a fibrous protein typically makes up 90% of the dry weight of hair [3]. e hydrogen atoms supplied by the sharpening agent weaken the cysteine molecular link causing the covalent di-Sulphide bond linkages to rupture and weaken the keratin. To some extent, sharpening also contributes to unhairing, as it tends to break down the hair proteins [4,5]. e conventional unhairing process in leather processing uses a lot of lime and sodium sulfide, which is hazardous and creates a lot of effluents. Under acidic conditions, sodium sulfide releases large amounts of hydrogen sulfide, which is a common source of fatal incidents [6]. Similarly, the conventional unhairing process emits a significant quantity of pollutants, including biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total solids (TS) [7].
Previously, several researchers attempted to mitigate the conventional unhairing-related problem by using plantbased and enzyme-assisted unhairing agents, which are environment-friendly options that decrease BOD and COD load in leather processing [1]. However, only a few plantbased and enzyme-assisted unhairing are performed in industrial applications, and currently, there is no commercially available environmentally friendly unhairing agent that can replace sodium sulfide [8,9]. is research aimed to extract eco-friendly unhairing agents from locally accessible plants in order to minimize tannery effluent and replace conventional unhairing agents.

Materials and Methods
e study used both qualitative and quantitative approaches to assess the properties of plants and the tanned leather properties. e research experimental work has been was carried out at the Ethiopian Institute of Textile and Fashion Technology, Bahir Dar University, Ethiopia, and Bahir Dar Tannery, Ethiopia. e study data were analyzed by using tables, pictures, and graphs.
2.1. Plant Collection, Drying, and Grounding. P.dodecandra leaves, S. incanum fruit and C. foetidissima fruit were collected from the regions of Amhara and Oromia states, in Ethiopia. P. dodecandra leaves and S. incanum fruit was cleaned, washed repeatedly with water, and cut into small chips for faster drying. e plant parts were dried for five days at room temperature and oven-dried at 120°C for 2 h. Similarly, C. foetidissima fruit was cleaned, washed repeatedly with water, and cut into small chips for juice preparation. All plants selected for the experimental work were shown in Figure 1.

Plant
Powder and Juice Preparation. P. dodecandra leaves and S. incanum fruit plant parts were individually weighed and ground in a high-speed multifunction grinder with a mesh size of 50-300. e reason behind grounding the plant parts was to maximize the surface area available for extraction, thereby raising the extraction rate. e powdered samples were placed in small plastic bags for further experiment activity. Similarly, C. foetidissima fruit was cut into small pieces and the plant juice was prepared.

Extracts Preparation.
In the study, separate extracts were obtained by mixing 0.5 kg C. foetidissima fruit sap, P. dodecandra leaves powder, and S. incanum fruit powder, and 80 mL of 99.5% methanol were used as a solvent. e plant extracts were prepared from each plant type in triplicate. e mixture was homogenized for 1 h using a magnetic stirrer at room temperature and the mixtures (juices) were separately filtered using a Whatman filter 1 paper, 15 cm disc. Each filtrate portion was then put in a glass beaker with aluminum foil on top and left to stand at room temperature for 48 h. e extracts were further purified using a centrifuge 5810 with 10,000 rpm centrifugation for 10 min at room temperature in order to remove insoluble materials. e filtrate was boiled in a water bath in order to evaporate the methanol and leave behind the extracts which was weighed and the percentage yield was calculated. e percentage of the plant fruit sap was calculated using the following method and their averages were used [10].
Fruits weight � Wf, Gross juice weight � Wj, Weight of the beaker � Wb, Net juice weight � Wb.

Juice content �
Net juice weight × 100 Fruit weight .
(1) e pH of each extract was measured using a pH meter and their values were recorded. As shown in Figure 2, each extract was then preserved in volumetric flasks in a refrigerator at 4°C, for later experiment usage.

Yield
Percentage of the S. incanum, C. foetidissima, and P. dodecandra Extracts. e amount of extracts from S. incanum fruits, C. foetidissima fruits, and P. dodecandra will depend on the plant age, growing geography, and methods of extraction. e amount of each plant extract was indicated in the following Table 1.

Phytochemical Tests.
e plant extract was subjected to preliminary qualitative phytochemical screening for steroids, alkaloids, flavonoids, tannins, saponins, and phenol-based on the following standard methods.

Test for Flavonoids.
e alkaline reagent test method was used to detect the presence of flavonoids in the extracts. A small amount of extract was treated with aqueous NaOH and HCl and observed for the formation of the yellow-orange color [11].

Test for Alkaloids.
Mayer's reagent test method was used to process the extracts (1.36 g of mercuric chloride and 5 g of potassium iodide in 100 ml of water). e presence of alkaloids is indicated by the formation of a yellow-colored precipitate [12].

Test for Phenolic
Compound. Ferric chloride test method was used to detect the presence of phenoloic compounds in the extracts. A 3-4 drops of 5% ferric chloride solution were added to the extracts. e presence of phenols is indicated by the formation of a bluish-black color [13].

Test for Saponins.
e Froth test method was used to detect the presence of saponin in the extracts. A 0.5 gm of extracts were mixed with 2 ml of water and shaken for 15 minutes in a graduated cylinder. e presence of saponins is shown by the formation of a 1 cm layer of foam [14].

Test for Tannins.
Ferric chloride test method was used to detect the presence of tannin in the extracts. A 0.5 g of crude of each plant extract was mixed with 10 mL of distilled water and boiled and then ltered. ree drops of 0.10% ferric chloride were added to the ltrate. e formation of brownish, greenish, or blue-black color was an indication of the presence of tannins [14].

Test for Steroid.
Chromatographic test method was used to detect the presence of steroids in the extracts. A 1 ml of the plant extract was added to 1 ml of concentrated tetraoxosulphate (VI) acid (H2SO4). A red coloration con rmed the presence of steroids [13].

Expermental Hypothesis: Optimization of Unhairing
Agents for Experiments. In the study, unhairing of sheepskin was conducted by the mixture of extracts unhairing solutions prepared from P. dodecandra leaves extract, C. foetidissima fruits extract and S. incanum fruits extract. Initially, the sheepskin was treated with conventional soaking agents (i.e., water and wetting agents) in order to rehydrate the skin, and then the unhairing extracts were applied to the skin. e reaction of a solution occurred at a low temperature. In order to obtain the optimum e ective unhairing ratio, three experiments were carried out under di erent parameters, which are shown in Tables 1-3.

Preparation of Unhairing Extract Solution.
Based on the unhairing recipe indicated in Tables 2-4, a 400 mL separate unhairing solution was prepared by mixing S. incanum extract, P. dodecandra extract, and C. foetidissima extract. After mixing the solution, 260 g/L of lime powder was added and stirred. e biome of the solution was checked. e prepared unhairing solution was kept for 24 h in order to enhance the solution mixture uniformity. e prepared   unhairing solution was applied to sheepskin using two different methods: a hair-saving method on the flesh side of the skin and a hair-burning method using a drum.

Preparation of Soaking Recipe for Unhairing Process through Hair-Saving Method.
Purification and defects-free raw sheep skin were used. e sheepskin soaking process was carried out by preparing a soaking recipe for the hairsaving method, as shown in the following Table 5. Table 5, half-side of the sheepskin was soaked in the soaking solution. en, the skin was weighed and painted with a paste containing 10% lime, 2% sodium sulfide, 15% water, and 0.2% wetting agent. e paint was applied on the flesh side of the skin. en, the treated sheep skin was covered well with wet gunny cloth and was kept in pile flesh to flesh for 5-6 h. Lastly, unhairing was carried out using mechanical action by using a dull knife. Table 6, half-side of the sheepskin was soaked in the soaking solution. en, the skin was weighed and painted with a solution containing S. incanum, P. dodecandra extract, C. foetidissima extract, and lime powder, which were indicated in Table 1. e paint was applied on the flesh side of the skin and piled for 5-6 h by the flesh to flesh side and grain to the grain side. Lastly, unhairing was carried out using mechanical action by using a dull knife. After the soaking process was completed liming was carried out.

Preparation of Sheepskin for Unhairing Process through
Hair-Burning Method. In the study, purification and defects-free raw sheepskin were used. e soaking process was carried out by preparing a soaking recipe prepared for hairburning method, as shown in Table 7.

Application of Conventional Unhairing through Hair-Burning Method (Control).
e hair-burning process was carried out in the drum according to the recipe shown in Table 6. A half-sheep skin was soaked in the drum containing 300% water, 5% lime, and 3% sodium sulfide. en, the drum was run for 10 min within 2 h and left overnight. By the next day, the skins were unhaired and re-limed for a day with a solution containing 5% lime ad 0.2% caustic soda.
When the sheep's skin were properly plumped, they are taken for unhairing and fleshing processes. Drums are used to accelerate the liming process and the rpm of the drum was set to 2-3 in order to avoid too much beating action. Completion of the liming process was decided by the characteristics desired in the final leather as well as the raw materials from which they are produced.

Application of Experimental Unhairing through Hair-Burning Method (Experimental).
e experimental unhairing (hair burning) was carried out in the drum according to the recipe indicated in Table 8.

Phytochemical Analysis of Plants Extracts.
Different studies revealed that the presence of bioactive compounds in the plant has a significant antimicrobial activity, which may enhance the quality of the leather treated with the plant extracts. As shown in Table 9, the S. incanum fruits extracts, C. foetidissima fruits extracts, and P. dodecandra leave extracts showed the presence of some bioactive compounds.

Flavonoids Detection.
Alkaline reagent test revealed a strong positive (++) presence of flavonoids only in S. incanum extract, as shown in Table 9. e present study investigation was similar to that of Lin et al. and Sbhatu et al [15,16], who reported the presence of flavonoids in S. incanum.

Saponins Detection.
e Froth test approach revealed the existence of strong positive (++) saponins in the extracts of S. incanum, C. foetidissima, and P. dodecandra, which were shown in Table 9. Correspondingly, different studies revealed the presence of saponins in the extracts of S. incanum [17,18], extracts of C. foetidissima [19,20], and extracts P. dodecandra [21,22]. Table 9, the ferric chloride test revealed the presence of a strong positive (++) phenols in the extracts of S. incanum, C. foetidissima and P. dodecandra. Similary, Prohens et al. and Belayneh et al. [23,24] reported the presence of phenols in S. incanum, Salehi et al. [20] reported the presence of phenols in C. foetidissima and Makonnen et al. and Namulindwa et al. [25,26] reported the presence of phenols in P. dodecandra.  [27,28] reported the existence of alkaloids in S. incanum, Ferguson [29] reported the existence of alkaloids       [26,30] reported the existence of alkaloids in P. dodecandra.

Tannin Detection.
In ferric chloride test, a strong positive (++) tannins were detected in S. incanum, C. foetidissima and P. dodecandra, which were shown in Table 9. Correspondingly, Sahle, Okbatinsae et al. and Desta et al. [28,31] reported the presence of tannins in S. incanum extracts, Salehi et al. and Pámanes et al. [20,32] reported the presence of tannins in C. foetidissima and Namulindwa et al. [26] reported the presence of tannins in P. dodecandra.
3.1.6. Steroids. e chromatographic test approach detected the presence of strong positive (++) steroids in S. incanum, C. foetidissima, and P. dodecandra, which were indicated in Table 9. Correspondingly, Ferguson [29] revealed the existence of steroids in S. incanum and C. foetidissima, and Ogutu et al. and Namulindwa et al. [26,30] revealed the existence of steroids in P. dodecandra.

Unhairing Effectiveness of the Plants Extracts.
e unhairing experiment was carried out with different mixing ratios of S. incanum extract, P. dodecandra extract, C. foetidissima extract, and lime powder under different temperatures, times, and pH values.
Experimental trial 1 was conducted under a constant temperature (25°C), Time (4 h), and lime powder (260 g/L) with a variable ratio of plant extracts. In the current study, the level of unhairing efficiency was judged by subjective by looking at the treated skin carefully. A high level of unhairing indicates that the hair was completely removed from the sheep skin, medium level of unhairing indicates that the hair was removed to some extent whereas low level of unhairing level indicates the hairs were removed in a low extent. As indicated in Table 10, the unhairing mixture ratio of 0.5 S. incanum, 0.5 P. dodecandra, 0.6 C. foetidissima and 260 g/L lime powder resulted in high level of unhairing effectiveness compared to the other experimental trials. As shown in Table 10, when the unhairing extracts mixing proportions were close to each other (0.5, 0.5, 0.6), the effectiveness of unhairing was enhanced.
In the study, Experimental Trial 2 was conducted under a constant temperature (30°C), Time (4 h) and lime powder 260 g/L. As indicated in the above Table 11, the unhairing mixture ratio of 0.5 S. incanum, 0.5 P. dodecandra, 0.6 C. foetidissima, and 260 g/L lime powder resulted in high level of unhairing effectiveness compared to the other experimental trials. Similar to Experimental Trial 1, when the mixing proportion of the extracts was close to each other and the effectiveness of unhairing were enhanced, which were shown in Table 11.
Experimental Trial 3 was conducted under a constant Temperature (35 C), Time (3 h) and lime powder 260 g/L. As indicated in Table 12, the mixture of 0.5 S. incanum, 0.5 P. dodecandra, 0.6 C. foetidissima and 260 g/L lime powder resulted in high level of unhairing compared to the other experimental trials. As indicated in Table 11, when the mixing proportion of the extracts was close to each other and the efficiency of unhairing was enhanced. Based on three Experimental trial results, it is observed that the unhairing mixture ratio of S. incanum, 0.5 P. dodecandra, 0.6 C. foetidissima and 260 g/L lime powder resulted in a high level of unhairing effectiveness. In the three experimental trials, varying the Temperature (25 C, 30 C, and 35 C) and Time (3 h and 4 h) has not affected the unhairing extracts' hair removal effectiveness.

FTIR Analysis. Fourier transforms infrared (FTIR)
spectroscopy is an important technique used for the chemical analysis of biological substances. Based on this, the raw sheepskin, experimentally unhaired sheep skin and conventionally unhaired sheep skin were characterized using in order to determine the sheep skin relative functional  group. e raw skin experimentally treated skin and conventionally treated skin FTIR% Transsimitence vs wavelength (cm − 1 ) result images were shown under Figures 3-5. As shown in Figures 3-5, there is a huge difference between raw skin, treated and conventional treated leather. Similarly, there was a difference between conventional and experimental treated leather that reveal a broad band in the range of 3550-3150 cm − 1 . Raw skin has more single bond, double bond, triple bond, and fingerprints and also has more peaks than experimental treated and conventionally treated leather. e FTIR spectra of untreated raw skin were shown in Figure 3. e FTIR spectra of Experimentally Treated Leather were shown in Figure 4. e FTIR spectra of conventionally Treated Leather were shown in Figure 5.

Comparison of Sheep Skin Treated with Experimental and Conventional Unhairing Agents.
e main objective of unhairing were to remove hair from sheepskin. e weakening of the hair depends on the breakdown of the disulfide link of the amino acid and cystine. e experimental and the conventional unhairing process result has been discussed as follows.

Experimental Unhairing through Hair Saving Method
Result Analysis. In the experimental saving (painting) process, the sheepskin was treated with a 400 mL unhairing containing a mixture of extracts of 0.5% S. incanum extract, 0.5% P. dodecandra extract, 0.6% C. foetidissima extract, and 260 g/L lime powder. is unhairing process was resulted in complete removal of hair from sheep skin after exposure of 3-4 h and 25-30°C. e unhairing agent extracted from the plant extracts not only removed the hair but also makes the sheep's skin clean and swell up. e plant-based unhaired sheep skin was to some extent similar to conventionally unhaired sheep skin. Sheepskin before treatment and sheep skin after treatment with unhairing through the hair-saving method was shown in Figure 6.

Experimental Unhairing through Hair Burning Method
Result Analysis. In the hair burning experiment, the sheep skin was treated with a 400 mL solution containing an extract mixture of 0.5% S. incanum extract, 0.5% P. dodecandra extract, 0.6% C. foetidissima extract, and 260 g/L lime powder has resulted in complete removal of hair from sheep skin after exposure of 12 h on a drum, which is indicated in Figure 7.
In the current study, the unhairng solution was prepared from a mixture of 0.5% S. incanum extract, 0.5% S. incanum extract, 0.5% P. dodecandra extract, 0.6% C. foetidissima extract and 260 g/L lime powder have effectively removed the hair from the sheepskin in both Hairs-saving and Hairburning unhairing process.      According to di erent studies, P. dodecandra fruits and S. incanum are rich in detergent agents namely saponins, which resulted in a clean leather, reduced smell, and substantially reduced amount of load released on the environment such as sul de, nitrogen, carbon-oxygen demand.
According to di erent literetures, the presence of calcium thioglycolate in S. incanum, the presence of zinc in C. foetidissima (pumpkin), and the presence of saponi ed (antimicrobials) in P. dodecandra leaves have resulted in the breakdown of disul de bond in keratin and ber open up. Correspondingly, the presence of lime in the unhairing agent enhanced the hair removal e ectiveness from sheep skin. On the other hand, the experimental plant-based unhairing extract has the ability to reduce bacterial attacks and also acts as a preservative in the leather. erefore, this study clearly indicates that the unhairing solution prepared from the plants has a good potential to replace the conventional sodium sul debased unhairing and liming process in the leather industry.

Physical Test Analysis of Experimentally and Conventionally Treated Sheep Leather.
e physical test analysis was carried out after sheepskin was treated with experimental and conventional unhairing recipes/. After the unhairing process, the sheepskins were passed through a similar leather processing stages. e nal leathers were tested and their physical test results are presented in Figure 8.

Tear Strength Determination.
Tear strength test methods were intended for the determination of load in kg required to tear the test sample. Tear strength testing was carried out according to ISO 3376 : 2011 and ASTM D2209-00 (2015) test methods. As indicated in Table 6, the sheepskin treated with the experimental extracts and conventional solution showed a comparable tensile strength (42.3 kg/cm) with conventionally unhaired leather (45.2 kg/cm), which was above the permissible limit for leather production making.

Tensile Strength Determination.
Tensile strength test methods were intended for the determination of tensile strength, temporary and permanent elongation at speci ed load, modulus, and elongation at break of sheep leather. e treated sample pieces were prepared according to ISO 3376 : 2011/ASTM D2209 -00(2015). As indicated in Figure 6, the study result indicates that the leather treated with plant unhairing extracts has a comparable tensile strength (140.1 kg/cm 2 and 143.5 kg/cm 2 ) and percent elongation at break (40.2 and 42.3), which were above the permissible limit for leather production making.

Grain Crack Strength Load and Grain Crack Strength
Distention. Consequently, the study revealed that the sheep skin treated with the experimental unhairing extracts and conventional solution showed a comparable Grain Crack Strength load (23 kg and 23.2 kg) and Grain crack strength distention (11.2 mm and 11.65 mm), which were above the permissible limit for leather production making.

Organoleptic Property Comparison of Experimentally and Conventionally Treated Leather.
Organoleptic property was carried out by nine experienced leather technologists working at an industry level and the average response were taken. As indicated in Figure 9, the organoleptic property of comparison between the conventional and experimental treated leather evaluation highest scores out of 9. e score result strength increases from 1 to 9. In the leather, the technologist response indicated that the conventionally treated leather and experimentally treated leather had the same result on grain pattern, uniformity of color, and fullness, however, they have a di erence in feel and general appearance. e experimentally treated leather has shown a better feel and general appearance than the conventionally treated leather. Figure 10, the use of unhairing agents extracted from locally available plants resulted in a reduction in pollution loads such as BOD, COD, TDS, and TSS in comparison with the conventionally treated sample. e conventionally treated sample showed more amounts of pollution loads in the unhairing process. is study revealed that the experiment treated sheep skin resulted in a COD, BOD, TDS, and TSS load of 62.7, 79, 81.8, and 27.2%, respectively. e experimental treated skin also shows complete unhairing along with a 59.3% reduction in the suspended solids level.

Pollution Load Analysis. As indicated in
Keys: COD: chemical oxygen demand; TDS: total dissolved solid; ppm e parts per million.   Journal of Engineering

SEM Analysis.
To study the e ect of the unhairing agents on the structural characteristics of the crust leather, scanning electron microphotographs were used to analyze the e ect of experimentally treated and conventionally treated on the crust. e SEM analysis was carried out using FEI-Quanta 200 scanning electron microscope based on the following SEM standards. In the study, the grain surfaces and the cross-section image of conventionally treated and experimental treated sheep skin crust were analyzed using Scanning Electron Microscope. As shown in Figure 11, it s observed that the      experimentally treated crust grain surface appears to be more even, open up, and smoother than the conventionally treated leather. Likewise, the experimentally treated crust pores are free of any hair residues and the fiber of collagen was more open than conventionally treated leather.

Conclusion
Extracted unhairing agents from locally available have a potential of removing hair from sheepskin. e current study result revealed the possibility of eliminating pollutioncausing chemicals such as sodium sulfide, lime, and sodium sulfide in the unhairing process. Consequently, the unhairing agent prepared from the plant source not only eliminated sulfide but also enhanced the softness and quality of the final leather. e current study resulted in the treated leather being knit, clean, and reduced the pollution load on the environment. Since lots of plant species are available in the world, the potential of related plant species for an unhairing agent needs to be studied in the future.
Data Availability e data collected and analyzed during this study are included in the paper and can also be accessed from the authors through a rational request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.