ABSTRACT
The tanning industry utilizes chrome salts for tanning despite them being considered environmental pollutants. Vegetable tanning is considered to be a greener alternative to chrome tanning with mimosa extract being the most commonly used. The presence of inadequate acacia trees in Kenya for mimosa production means that the country majorly relies on imports which results in an increase in their prices leading to an increase in cost of production. This study was formulated to determine the viability of coffee pulp as a source for vegetable tannins. Twelve samples were collected from Yadini coffee factory in four different days. The tannin content was quantitatively determined by the hide powder method. The quality of the leathers was determined by carrying physical tests on tanned goatskins according to IUP methods. A statistical t test was used for comparison of coffea arabica pulp and mimosa tannin content and physical properties of resultant leathers. It was established that C. arabica pulp had a tannin content of 5.04% and a tanning strength of 2.26 compared to mimosa extract with a tanning content of 64% and a tanning strength of 2.82 with the two tannins being of the condensed type. This showed that there was a significant difference (p<0.05) between the tannin content and tanning strength of mimosa and C. arabica tannins. The physical characteristics of C. arabica pulp tanned leather was 14.72±2.22N/mm2 and19.09±1.60N/mm2 tensile strength, 62oC shrinkage temperature, 48.00±14.15 N/mm, 38.12±3.13N/mm tear strength, grain crack and grain burst of 4.52±0.31mm and 5.93±0.28mm respectively and a change in colour at 100000 flexes for flex endurance. Mimosa tanned leather had 24.19±2.25N/mm2 and 27.20±3.26N/mm2 tensile strength, 83oC shrinkage temperature, 75.97±8.68N/mm, 72.08±8.19N/mm tear strength, grain crack and grain burst of 7.47±0.09mm and 8.25±0.15mm respectively. There was no damage at 100000 flexes for flex endurance. The t test used for comparison showed that there was a significant difference (p<0.001) for tensile strength, tear strength, shrinkage temperature, ball burst and flex endurance. The study concluded that the tanning strength of coffee pulp was more than the minimum 1.5 recommended for vegetable tanning materials. The physical properties exceeded the minimum recommended limits although they were less comparable to mimosa tanned leather. It was recommended that further research to be conducted on the penetration of C. arabica pulp tannins in the pelt as the coffee tannins in their natural form did not penetrate making their use in tanning in this state difficult.
Table of Contents
DECLARATION ii
ACKNOWLEDGEMENTS iv
LIST OF TABLES viii
LIST OF FIGURES ix
LIST OF PLATES x
LIST OF APPENDICES xi
LIST OF ABBREVIATIONS xii
ABSRACT xiii
CHAPTER 1. INTRODUCTION
1.1. Background 1
1.2. Problem statement 2
1.3. Objectives 3
1.3.1. General objective 3
1.3.2. Specific objectives 3
1.4. Research Hypothesis 3
1.5. Justification 4
CHAPTER 2. LITERATURE REVIEW
2.1. A Historical overview 5
2.2. Chromium tanning 6
2.3. Vegetable tanning 6
2.4. Classification of vegetable tannins 8
2.4.1. Hydrolysable tannins 8
2.4.2. Condensed tannins 9
2.5. Extraction of vegetable tannins 10
2.6. Coffee 12
2.7. COFFEE PULP 16
2.8. The tanning process. 17
CHAPTER 3. MATERIALS AND METHODS
3.1. Sampling area 21
3.2. Sample selection and preparation 22
3.3. Test for tannins 24
3.4. Test for condensed and hydrolysable tannins 24
3.5. Test for the strength of tanning of vegetable tannins 25
3.5.1. Hide powder preparation 25
3.5.2. Chrome hide powder preparation. 25
3.5.3. Determination of moisture and total solids 25
3.5.4. Determination of total soluble solids 26
3.5.5. Preparation of chrome alum solution 27
3.5.6. Preparation of gelatin reagent 27
3.5.7. Determination of non-tannins 27
3.5.8. Determination of tannins 28
3.5.9. Determination of alkalinity and acidity 28
3.6. Tanning 28
3.7. Comparison of physical properties of coffee pulp and mimosa tanned leathers 29
3.7.1. Sampling and conditioning. 29
3.7.2. Shrinkage temperature 29
3.7.3. Flexing endurance 30
3.7.4. Tear load 30
3.7.5. Resistance to grain cracking 30
3.7.6. Tensile strength 31
CHAPTER 4. RESULTS
4.1. Test for presence and type of tannins 32
4.2. Analysis of tannin content and tanning strength of coffea arabica pulp 33
4.3. Physical characteristics of coffea arabica and mimosa tanned leathers. 35
4.3.1. The shrinkage temperature 36
4.3.2. Tensile strength and elongation 37
4.3.3. Tear strength 38
4.3.4. Grain crack and grain burst 39
4.3.5. Flexing endurance 40
CHAPTER 5. DISCUSSION, CONCLUSIONS AND RECCOMENDATIONS
5.1. Presence and type of tannins 42
5.2. Analysis of tanning content and tanning strength 42
5.3. Vegetable tanning with coffea arabica pulp and mimosa 44
5.4. Physical properties of the tanned leather 45
5.4.1. Shrinkage temperature 46
5.4.2. Tensile strength and elongation 47
5.4.3. Tear strength 49
5.4.4. Ball burst 49
5.4.5. Flex endurance 50
5.5. Conclusions 50
5.6. Recommendations 51
REFERENCES 52
APPENDICES 67
LIST OF TABLES
Table 4.1 Phytochemical test results for coffee arabica pulp and mimosa 32
Table 4.2: Summary of Tanning strength, Tannins and non-tans of coffee arabica and
mimosa 34
Table 4.3: Shrinkage temperature of coffee arabica pulp and mimosa tanned leathers. 37
Table 4.4: Tensile strength and elongation of coffee arabica pulp and mimosa tanned leathers. 38
Table 4.5: Tear strength of coffee arabica pulp and mimosa tanned leathers 39
Table 4.6: Ball burst test results for coffee arabica pulp and mimosa tanned leathers. 39
Table 4.7: Physical characteristics of coffee arabica and mimosa tanned leathers. 40
LIST OF FIGURES
Figure 2.1: Gallic acid and Ellagic acid (Hagerman 2002.) 9
Figure 2.2: Flavan-3-ol structure and epicatechin-[(4β->8)-epicatechin]15 –(4β->8)-catechin10 Figure 2.3: The Structure of Coffee berry (Santos et al., 2021) 14
Figure 2.4: The various processing methods of coffee cherries (Wintgens, 2004) 15
Figure 2.5: Coffee pulping process with various products and by-products 16
Figure 3.1: A Map of Kiambu county and its constituencies 21
Figure 4.1: Variations in Components of different Tanning materials. 35
LIST OF PLATES
Plate 2.1: Coffee arabica plant grown in Yadini coffee farm 12
Plate 3.1: Drying of coffee arabica pulp in Thika Kiambu County. 22
Plate 3.2 Dried coffee arabica pulp 22
Plate 3.3: Ground coffee arabica pulp 24
Plate 4.1: Brown dry mimosa tanned leather being toggled. 36
Plate 4.2: A brown black coloured coffee arabica tanned leather. 36
LIST OF APPENDICES
Appendix 1:Process recipe for hide powder 67
Appendix 2: Recipe for the tanning of the leather. 68
Appendix 3:Physical characteristics of leather observed. 70
LIST OF ABBREVIATIONS
BIS - Bureau of Indian Standards.
DPHPT- Department of Public Health, Pharmacology and Toxicology. IUP - Physical Test Methods.
IULTCS- International Union of Leather Technologists and Chemists. KIRDI- Kenya Industrial Research and Development Institute.
N/mm2- Newtons per square millimeter.
UNIDO- United Nations Industrial Development Organizations.
CHAPTER 1
INTRODUCTION
1.1. Background
Tanning is the transformation of an organic material liable to decay into a stable material that resists putrefaction by bacteria with an increase in the hydrothermal stability and unique physical and chemical modifications imparted on tanned hides and skins by the tanning agent (Yao et al., 2019). The organic material referred here is the hides and skins that are gotten as one of the waste items of the meat industry. These hides and skins are mainly gotten from cattle, sheep and goats in Kenya, although ostrich skins, fish skins and skins from crocodiles are available. There are two main types of tanning; mineral tanning and vegetable tanning (Maina et al., 2019), the most common of the mineral tanning is chrome tanning which can be traced back to just over 100 years ago. It has been the most widely used tanning agent in the recent past because chromium forms leather with a hydrothermal stability of more than100 oC which is very versatile(Liu et al., 2019). This benefit is however compared to the effects that the resultant wastes produce. These wastes range from solid tanned wastes, liquid wastes to sludge (Hu et al., 2011; Rigueto et al., 2020). Control measures have been put in place i.e., to see whether the uptake of chrome can be maximized so as to reduce the percentage of chrome in wastes. However, this has proven to be a difficult task as complete uptake of chromium has been difficult to achieve (Pradeep et al., 2021). The uptake increment also only solves the problem in liquid wastes and sludge but fails to solve it in solid wastes.
Mimosa has been the most commonly and widely used vegetable tannin in the world especially in production of heavy leathers such as sole leathers. However, in Kenya, mimosa that is used is mainly from imports as there aren’t enough acacia trees to support local production of these tannins resulting in an increase in their price and eventually an increase in the cost of production. Some studies were carried out in Kenya in search of alternative sources for vegetable tannins. Kuria, (2015) studied various vegetable tannins in Laikipia county Kenya to ascertain their tanning potential. The study found that Acacia xanthophleo, Acacia nilotica and Hagenia abyssynica had enough tannins for commercial extraction. Kimaiga, (2016.) studied Plectranthus barbatus as an alternative source. Although these studies showed that these plants had sufficient vegetable tannins for extraction, the availability of these plants in sufficient quantity to sustain production is still not enough. It is for this reason that this study was carried out to search for an alternative vegetable tanning material that is available in sufficient quantities for production.
1.2. Problem statement
Chrome tanning is known to cause environmental pollution globally because the chromium offered into the tanning drum is not completely utilized and end up in the effluent (Ozgunay et al., 2018). High concentration of this compound in the effluent complicates the treatment process and hence more cost is incurred. Chrome waste occurs in three forms, i.e. liquid waste, solid tanned waste and in sludge(Sundar et al., 2011). According to Liu et al., (2019), approximately 70% of chrome salt added to the tanning liquors is absorbed by the pelt and the remaining more than 30% is released into the effluent. When chrome is discharged in even low amounts, it is very toxic as it interferes with daphnia thus disrupting the fish food chain and even the photosynthesis of aquatic plants (Wu et al., 2012). It also adversely affects human health if ingested or inhaled. The pickling process that precedes tanning proper for chrome tanning uses sodium chloride which is drained into the effluent. Salt is known to have very high detrimental effects to every environmental sphere that it is disposed to due to its salinity levels which tend to destroy all kinds of vegetation around it and in fresh aquatic environment. According to Zhang et al., (2017), the high salt levels tend to dehydrate the aquatic animals such as fish to death. As stated before, the conventional tanning methods have more negative effects on the environment as compared to the vegetable tannings. When it comes to vegetable tannins, different tannins have a varied degree of ecotoxicity to the aquatic environment and human toxicity, e.g., mimosa is more toxic to the aquatic environment as compared to gambier tannins. However, gambier is more expensive compared to mimosa (Alfarisi and Ciptomulyono, 2016). Thus, there is need for a vegetable tannin which has low aquatic ecotoxicity and easily available.
1.3. Objectives
1.3.1. General objective
To evaluate the tanning viability of coffee pulp from Coffea arabica in Yadini farm, Kiambu County, Kenya.
1.3.2. Specific objectives
i. To identify the type of tannins, present in pulp of Coffea arabica grown in Yadini farm, Kiambu County, Kenya.
ii. To determine the tannin content and tanning strength of Coffea arabica pulp.
iii. To compare the physical characteristics of goatskin leather tanned with Coffea arabica pulp and goatskin leather tanned with standard commercial mimosa.
1.4. Research Hypothesis
Ho: Coffea arabica pulp contains sufficient tannin content and strength for effective tanning of leather.
H1: Coffea arabica does not contain sufficient tannin content and strength for effective tanning of leather.
1.5. Justification
Scientists have been able to see the effects of chromium tannage wastes to the physical environment and the biological environment. Vegetable tannage has been proposed as a suitable replacement for chrome tannage and may as well be applicable to all other forms of mineral tannage. However, vegetable tannins, although available in Kenya, are slightly higher priced as compared to basic chromium salts. This coupled with the fact that chromium tanning uses 6-8% of chrome salts whereas the vegetable tanning uses 10-15% of tannins which is approximately twice the amount used in chromium tanning leads to an increase in cost of production which limits the profit margin for companies hence most small-scale industries opt to use chrome salts. Tannins from coffee pulp would be a viable option due to their availability as the coffee industry produces a lot of pulp as a byproduct. Coffee pulp has been found to possess bioactive materials such as tannins which can be used in leather manufacture. The byproduct is readily available in large quantities which will translate to high amounts of coffee pulp tannin. The free source of coffee pulp will ensure that the market prices for coffee pulp tannin is cheaper making tanning a cheaper enterprise as compared to other vegetable tannins. It is for this reason that the study was undertaken to seek out a different tannin material with the same or better qualities as compared to the conventional tannins but which will be both cheap and readily available for most small-scale tanners.
Click “DOWNLOAD NOW” below to get the complete Projects
FOR QUICK HELP CHAT WITH US NOW!
+(234) 0814 780 1594
Login To Comment