Mechanical and Water Interaction Properties of Polymeric Films Produced with Starch and Gelatin Extracted from Leather Waste as Affected by Different Composition

by Bianca Santinon Scopel, Laís Bavaresco, Júlia Mascarello, Aline Dettmer and Camila Baldasso

In this work, gelatin extracted from chromed leather wastes (CLW) was used to produce polymeric films with starch. Different compositions (glycerol or sorbitol as plasticizers, 0, 10 and 20% of plasticizer and 6.4, 8.0 and 9.6 g of starch for each 2.4 g of gelatin) were evaluated. Water solubility ranged from 17 to 28% and elongation at break from 6.5 to 133.8%. The opposite effect was noticed for tensile strength. Small amounts of chromium (2.4 – 2.9 mg/kg of film) would allow the films application in agriculture, where nitrogen released after films degradation would act as a nutrient.

JALCA January 2019

Machine Vision Inspection System for Detection of Leather Surface Defects

by Malathy Jawahar, K Vani and N K Chandra Babu

Leather quality inspection is very important in assessing the effective cutting value that can be obtained from the leather. Current practice involves an expert to inspect each piece of leather individually and detect defects manually. However, such a manual inspection is highly subjective and varies quite considerably from one assessor to another. Often this subjectivity leads to dispute between the buyer and the seller of the leathers and hence attempts are made to automate this. Automatic leather defect classification is a challenging research problem due to the difficulties that arise when segmenting defects from the leather background and determining the characteristics that describe the defects objectively. The present study describes application of machine vision system to capture leather surface images and the novel multi-level thresholding algorithm to segment defective and non-defective regions of leather followed by texture feature extraction to objectively quantify the leather surface defects. A dataset consisting of 90 leather images comprising 20 good leather and 50 defective samples has been used in the study. Experimental results on the leather defect image library database achieved an accuracy of 90% using neural network as classifier, confirming potential of using the proposed system for automatic leather defect classification.

JALCA January 2019

Antioxidant Activity of Keratin Hydrolysates Studied by DSC

by Ján Matyašovský, Ján Sedliacik, Peter Šimon, Igor Novák, Tomasz Krystofiak, Peter Jurkovic, Peter Duchovic, Mariana Sedliaciková, Zuzana Cibulková, Matej Micušík and Angela Kleinová

Due to the high content of thio-aminoacids, (i.e., methionine and cysteine) and the structural intermolecular disulfide bonds, this study has focused on new biopolymer keratin antioxidants. The antioxidant activity of keratin hydrolysates in polyethylene glycol (PEG) matrix has been studied using the differential scanning calorimetry (DSC) under non-isothermal conditions. The experimental results have been evaluated and kinetic description of the oxidation induction periods have been carried out using the Bethelot-Hood temperature function. The length of induction periods has been assessed for all temperatures using the kinetic results. In order to compare the stabilizing effect of keratin hydrolysates, protection factors and antioxidant effectiveness have been calculated. The results have shown that the antioxidant activity of keratins strongly depends on the hydrolysis process. The protection factors decreased with increasing temperature and decreasing concentration of keratin. Based on our previous experience, we propose that the qualitative trend presented in this work can also be applied for other matrices than PEG. Keratin hydrolysates and their modifications with antioxidant properties significantly reduced formaldehyde emissions from urea-formaldehyde adhesives.

JALCA January 2019

Insights into the Molecular Composition of the Skins and Hides used in Leather Manufacture

by Rafea Naffa, Catherine Maidment, Geoff Holmes and Gillian Norris

Increasing demand for information about the effects of the beamhouse processes on animal skins and hides led to the need to determine the differences among different animal skins and hides at molecular level which results in significant changes in their strength. This is a comprehensive study of the molecular components of four animal skins commonly used to manufacture shoes, clothing and furniture to identify common indicators of skin strength. First, the strength of each species was assessed using tear strength and the denaturation temperature. Then the concentration of the following molecular compounds: amino acids, natural collagen crosslinks and glycosaminoglycans (GAGs) were determined. Significant differences in their molecular compositions were found particularly the types and amount of the natural collagen crosslinks which are known to be essential for skin strength. We found that sheep skin contained the lowest collagen content and highest GAG concentrations compared to goat and deer skins and cow hide. To the best of our knowledge, this is the first time where the collagen crosslinks of skin and hide of different species are measured and compared. This study shows that different species have different underlying molecular composition of skins and hides resulting in strength differences. This understanding will help to modify the current leather processing protocols to produce stronger leather.

JALCA January 2019

Suitability of Pore Measurement Methods for Characterizing the Hierarchical Pore Structure of Leather

by Xiu He, Ya-nan Wang, Jianfei Zhou, Haobo Wang, Wei Ding and Bi Shi

Pore structure of leather plays an important role in leather-making process as well as in characterization of comprehensive properties of leather. In this study, scanning electron microscopy, mercury intrusion porosimetry (MIP), capillary flow porometry and nitrogen adsorption techniques were used for characterization of the hierarchical pore structure of leather. From the comparison, MIP was found to be more suitable for pore measurement of leather in consideration of its extensive measuring range (from 5.48 nm to 120 um), high accuracy (measuring both through pores and blind pores in leather) and satisfactory repeatability (with RSD of 3.25% and 1.73% for average pore diameter and porosity, respectively). Then the MIP test conditions were optimized. The appropriate conditions were found to be that a leather sample (approx. 3 cm × 2 cm and 0.6 g) is used for determination with a stem volume around 50%. Blank correction is conducted in the measurement with the maximum pressure of 33000 psia and the equilibration time of 10 s. In general, the characterization of the hierarchical pore structure of leather by MIP is a meaningful aid to explore the relationship between structure and property of leather.

JALCA February 2019

Studies on the Ethiopian Camel Hides for Their Suitability for Making Leather

by M. Belay, R. Karthikeyan, V. John Sundar and R. Aravindhan

Ethiopia has the largest livestock population in the African countries, providing a strong raw material base for the growing leather and leather products sector. The main source of raw material for the Ethiopian tanning industry comes from sheep, goat and cattle. Since the Ethiopian leather industry is booming, the industry is now looking to exploit the alternative raw materials available in the country. Camel (Camelus dromedarius) is one of the most important livestock in the East African countries. Due to lack of awareness and technology, most of the hides are not utilized fully by the tanners. Hence an attempt has been made in the present study to exploit the camel hides as an alternative source of raw material for the growing Ethiopian leather industry. Histological analysis of the camel hide has been carried out at different stages of processing. Based on the histological understanding, the strategy for making suitable leather from camel hide was established. The raw material has also been characterized for fat, nitrogen and collagen content. The raw material has been converted into finished leather by using suitable tanning methodology and the leathers were utilized for the preparation of different types of end products. Finished leathers have been developed and the physical and chemical properties have also been evaluated. The results obtained from the chemical and physical tests revealed that the raw material is suitable for the manufacture of upper leather.

JALCA February 2019

Influence of the Chromatographic Conditions of the EN ISO 17226-1 Standard “Determination of formaldehyde content in leather. Part 1. Quantification by HPLC” on the Robustness of the Method

by Albert M. Manich, Sara Cuadros, Agustí Marsal, Maria-Reyes Reyes and Joaquim Font

Given the carcinogenic character of formaldehyde, it should be reliably determined in any substrate. The EN ISO 17226 Standard is the Official Method to quantify formaldehyde in leather using either the chromatographic or the colorimetric methods. In cases of discrepancy between results, according to the ISO Organization, preference should be given to the chromatographic method (EN ISO 17226-1 Standard) instead of the colorimetric one (EN ISO 17226-2 Standard). The EN ISO 17226-1 Standard recommends chromatographic conditions of column, mobile phase composition and flow rate. The paper studies the influence of changes in flow rate, composition of the mobile phase and separating columns recommended by the EN ISO 17226-1 Standard for the determination of formaldehyde content in leather. It has been made relevant that small variations in the flow rate and differences in mobile phase compositions ranging from 35/65 to 45/55 Water/Acetonitrile does not significantly affect the results of formaldehyde concentration. As regards the different separating columns, non-significant differences between them were observed. However, considering the effectiveness and the retention time of the separating columns, the solid-core particle (Cortecs®C18) column can be recommended because it has in excess the capacity to separate the formaldehyde peak from that of the residual DNPH reagent in less than 2 minutes which is lower than those of the other columns tested. Consequently, the productivity of the analytical laboratories is improved.

JALCA February 2019

Analysis of the Processing Histology of Mink Skin

by Meina Zhang, Yao Tian, Yongguang Wang and Zongcai Zhang

Most people around the world regard mink skin as luxurious commodities, since the mink hair is generous and guard hair length is moderate. However, a variety of reasons will attribute to hair loss or orientation phenomenon of upper hair in the processes. The paper studied the processing histology of mink in the processing, which could build a scientific foundation to optimize the process, improve the technical skills and improve product quality. Mink skin samples used in the experiment were taken from soaking, degreasing, bating, pickling, and tanning processes. The photomicrographs were observed by bio-optical microscope. Besides, samples were performed by frozen section method and stained with iron hematoxylin staining method as well as Gill modified hematoxylin staining method. It is found that the hair follicles of the mink were distributed irregularly in the form of compound hair follicles or individual hair follicles. Mink fat glands were very developed. In other words, each hair follicle generally was surrounded by a pair of fat glands. With the increase in degreasing time, the number of fat cells in the fat glands was reduced and the fibers around the hair follicles were initially dispersed. The voids between the collagen fibers became larger and more fully loose after the processes of bating and pickling. In addition, the collagen fiber wove more orderly and closer by tanning. In the case of pickling and bating, most of the hair follicle openings were opened, which could abate the chained force between hair and the follicles and/or the dermal papilla.

JALCA February 2019

Pilot production of chrome-tanned leather without formation of hexavalent chromium by treatment with a combination of inhibitors

by Ogata, Koko; Inatsugi, Toshinori; Hattori, Shunji; Kagawa, Yoshiko; Yoshimura, Keiji; Takahashi, Koji

A combination of inhibitors, namely a mixture of 1.0mmol of 3(2)-t-butyl-4-hydroxyanisole, 0.01 mmol of ascorbic acid, and 0.001mmol of collagen peptide exhibiting complete inhibition of C6+ formation on a laboratory-scale, was applied to produce chrome-tanned upper leather without formation of Cr6+ in the actual manufacturing line of a tanner. In this study, the following two methods were used for application of the combined inhibitor; (1) spraying with the combined inhibitor solution before finishing, using twice the volume of the dry leather weight after fat-liquoring; and (2) coating with base-coat containing the combined inhibitor before top coating in the finishing process, using twice the volume of the dry leather weight. Each inhibitor-treated leather contained chemical components similar to those of typical leather produced without the combined inhibitor, and exhibited perfect inhibition of Cr6+ formation, even if heat-aged. In addition, the physical strength of the inhibitor-treated leathers was higher than that of leather produced usually without inhibitor. In particular, the surface strength (ball burst) of the treated leathers was twice that of the untreated leather. These results indicate that this combination of inhibitors could be effectively applied to industrially produce Cr-tanned leather not only
without C6+ formation but also with an improved physical strength.

SLTC Journal Jan-Feb 2019

Investigation of antibiotic-resistant enterobacteriaceae isolated from soaked sheepskins and cattle hides

by Birbir, Meral; Yazici, Eda; Caglayan, Pinar

Antimicrobial resistance of bacteria in human and veterinary medicine has been examined for many years, but there is no information about antimicrobial resistance of Enterobacteriaceae isolated from soaked sheepskins and cattle hides. Therefore the antibiotic resistance of Enterobacteriaceae isolated from soaked sheepskins and cattle hides was investigated. The antibiotic resistance of soaked skin isolates (Citrobacter freundii, Citrobacter koseri, Cronobacter sakazakii, Enterobacter amnigenus, Enterobacter cloacae, Morganella morganii, Proteus mirabilis, Providencia rettgeri ) and soaked hide isolates (Citrobacter koseri, Cronobacter sakazakii, Morganella morganii, Providencia rettgeri, Serratia marcescens, Serratia plymuthica, Serratia rubidae) towards 24 different antibiotics were examined using the disc diffusion method. Among thirteen skin isolates, the percentages of resistance against antibiotics used were aztreonam 92%, ampicillin 69%, ceftriaxone 69%, streptomycin 62%, cephalothin 62%, amoxicillin/clavulanate 62%, ceftazidime 61%, nalidixic acid 54%, ciprofloxacin 54%, chloramphenicol 46%, piperacillin/tazobactam 46%, cefuroxime sodium 46%, tetracycline 31%, sulfamethoxazole-trimethoprim 15%, cefoxitin 15%, ampicillin/sulbactam 15%, kanamycin 15%, tobramycin 8%, meropenem 8% and imipenem 8%. Among ten hide isolates, the percentages of resistance against antibiotics were, ampicillin 80%, amoxicillin/clavulanate 80%, tetracycline 70%, cefuroxime sodium 70%, streptomycin 60%, aztreonam 50%, ceftriaxone 40%, chloramphenicol 30%, ceftazidime 20%, cephalothin 20%, nalidixic acid 30%, cefoxitin 20%, ampicillin/sulbactam 20%, piperacillin/tazobactam 20%, ciprofloxacin 20% and kanamycin 10%. While all skin isolates were susceptible to amikacin, gentamicin, ofloxacin, and norfloxacin, all hide isolates were susceptible to amikacin, gentamicin, tobramycin, meropenem, sulfamethoxazole-trimethoprim, norfloxacin and ofloxacin. As a conclusion, the species of the family Enterobacteriaceae which were resistant to the antibiotics used in human and veterinary medicine were detected on the soaked skins and hides in the leather industry.

SLTC Journal Jan-Feb 2019

Preparation of oxidised polyvinyl alcohol using hydrogen peroxide and its application for collagen modification

by Baohua Liu; Ya-Nan Wang; Wei Ding; Bi Shi

Polyvinyl alcohol (PVA) was oxidised by hydrogen peroxide to prepare oxidised polyvinyl alcohol (OPA). The chemical structure of OPA was characterised by FTIR, SEC and potentiometric titration. PVA was ruptured into fragments along with the formation of terminal aldehyde and carboxyl groups after oxidation. Then the modification effect of OPA on collagen was investigated. A Schiffʼs base was formed between the aldehyde group of OPA and the amino group of collagen under alkaline conditions, without altering the triple helical structure of collagen. OPA promoted the moderate aggregation of collagen through chain entanglement, and enhanced the thermal stability of collagen. The main reaction between OPA and collagen was proposed as grafting of the single aldehyde component of OPA onto the collagen chain, which was quite different from the cross-linking action of glutaraldehyde. These results suggest the prospect of designing collagen-based biomaterial with a proper range of strength by OPA.

SLTC Journal Jan-Feb 2019

Comparative study of glucose and sulfur dioxide reduced chrome powders

by Ding Xiaoliang; Shan Zhihua; Fu Xianbing; Sun Hu; Ying Xiaoyan

The chrome tanning agent is always an important material for leather manufacture because of its tanning power and the leatherʼs sensory appeal which cannot be achieved by other tanning agents. The maturation of the chrome tanning technique over one hundred years, allows the leather produced to be distinguished by its nuances. Nowadays, it is beneficial to review the function of chrome tanning agents again because the standards of new market values and environmental requirements require more sophisticated application techniques. The characteristics of two kinds of chrome tanning agents, such as the glucose reduced chrome powder (GCr-S) and the sulfur dioxide reduced chrome powder (SCr-S), were explored by modern analytical detection methods, including the hydrolysis and spectral absorption features; the penetration velocity and absorption rate in pickled hides. The application performance of the two chrome tanning agents used in tanning and retanning was characterised by the handle and physical/mechanical properties of leather after dyeing and fatliquoring. Because of their different composition, structure and hydrolysis characteristics of their solutions, the differences between the two chrome tanning agents in the tanning powers and the differences between the two kinds of leathers in appearance, strength and histological state are represented respectively. It was suggested how to choose and use the type of chrome tanning agent to meet the quality requirements of the leather.

SLTC Journal Jan-Feb 2019

Unhairing of bovine skin with fungal enzymes by immersion and spread throughout the epidermis

by Garro, Maria Laura; Galarza, Betina; Greco, Carlos; Hourse, Roque

The use of enzymes during unhairing in the leather industry to partially reduce sulfide can decrease H2S emission to almost 50%. However the proteolysis needs to be controlled to prevent collagen damage. In bovine epidermis, the stratum corneum plays a crucial role as a hydrophobic barrier. In order to facilitate the diffusion of enzymes, it is necessary to generate channels through this barrier to allow enzymes pass without damaging the collagen. In an ideal enzymatic unhairing the proteolytic activity should be restricted to the basal lamina and pilosebaceous unit. During this experiment, fungal enzyme extracts (CE) were applied on bovine skin in the soaking and unhairing steps as part of the tanning process. The skin contacted with the solutions in two different ways: in direct contact with the epidermis (Mode I) and immersed in the solution (Mode II). Various keratinolytic fungi, previously isolated and selected from different soil samples were used: Neurospora crassa, Verticillium albo-atrum, Trichophyton ajelloi, Chrysosporium sp, Aspergillus sydowii, Paecilomyces lilacinus and Acremonium murorum. The fungal isolates were cultivated under solid state conditions using hair waste obtained from the hair-saving unhairing process as substrate. Enzyme extracts were characterized according to their keratinolytic and proteolytic activity and protein content. Once the immersion with fungal enzymes was finished, the treatment with N. crassa, T. ajelloi, Chrysosporium sp, A. sydowii and
P. lilacinus, showed unhaired skin and epidermis removed. After the contact between the epidermis and fungal enzymatic extract of T. ajelloi empty hair follicles were observed. The morphological changes were studied with SEM (Scanning Electron Microscopy).

SLTC Journal Jan-Feb 2019

Preparation and application of a novel cationic fatliquoring agent

by Yang Hong; Jin Liqiang; Wang Yulo; Wang Jinlong

In this work, a novel cationic fatliquoring agent YH was prepared by two steps. Firstly, a cationic emulsifier YW based on fatty acid triethanolamine ester was synthesized by using stearic acid,
triethanolamine and benzyl chloride. Then, YH was obtained by mixing a certain amount of YW, nonionic surfactant and neutral oil. The composition of YH was optimized by its application behaviour as a fatliquor. The structure of YW was characterised by infrared spectroscopy and 1H-NMR. The surface tension of YW aqueous solution was determined by using a surface tension meter. The stability, particle size and zeta potential of YH were studied. The results show that YH exhibits high centrifugal stability and electrolyte resistance with an average particle size of 24.44nm and zeta potential of 60.8mV at pH4.5. The leather samples treated by YH show high softness, tensile strength and tear strength. When YH was used as a dye-fixing agent, it could promote the absorption and fixation of anionic dyestuff, and improve the dry/wet fastness of leather and the colour fastness of washing.

SLTC Journal Jan-Feb 2019

Investigation into the hazards of finished Cr-tanned leather as both product and waste

by Liangqiong Peng; Yue Li; Weimo Han; Wenjun Long; Wenhua Zhang; Bi Shi

In this study, the hazardous substances in finished chrome-tanned leather and in leachates were determined and evaluated based on ISO or national standards, and the overall toxicity toward
Photobacterium phosphoreum of the leachates was assessed. No restricted hazardous substances, such as Cr(VI), HCHO and carcinogenic dyes in leathers exceeded the thresholds proposed in the criteria for eco-label leather products. Chrome leathers were then leached with deionized water with a solid/liquid ratio of 1:20 to simulate rainwater leaching, and the heavy metals as well as organic compounds in leachates were analysed by ICP-OES, spectrophotometry, and GC-MS. The total chrome, Cr(VI) and TOC in the leachates of leathers were about 2.6-2.8, 0 and 237-277mg/L, repectively, and the low contents of hazardous substances in leachates showed that leather should not be considered as toxic waste when discarded. However, the biotoxicity assays of the leachates from leathers showed quite a high luminescence inhibition rate of about 97-98%, suggesting a hazard to aquatic organisms. Though the leachable chrome showed the greatest concentration in general, the toxicity of leachates seems complicated and further studies are needed.

SLTC Journal Jan-Feb 2019

Women in leather

by Tony Covington

March 8, 2018 was International Womenʼs Day, a day to highlight the roles and achievements of women in society. 2018 was celebrated in the UK in remembrance of the campaign by the Suffragettes and Suffragistes to achieve votes for women, a campaign which saw the beginning of victory in 1918. These events give pause for thought, if only because our industry has long been dominated by men. I regard myself as a feminist, so it has been something of a mission to play a part in supporting the roles of women in our industry. Consequently, I have long been aware of the powerful women in the leather industry, especially in research, both now and in the past. I thought it would be instructive to recall some names. In my admittedly selective and non-comprehensive alphabetical list, there are some who were selected by Graham Lampard in his review of the most influential leather people from the beginning of the last century.

SLTC Journal Jan-Feb 2019

Stability of collagen in ionic liquids: Ion specific Hofmeister series effect

by Tarannum, Aafiya; Raghava Rao, J.; Fathima, N. Nishad

In protein-ionic liquids (ILs) interactions, anions play an important role. In this work, imidazolium-based ILs (IILs) with varying anions namely dicyanamide (DCA), hydrogen sulfate (HS), dimethyl phosphate (DP), acetate (A), sulfate (S) and dihydrogen phosphate (DHP) have been chosen with the aim of understanding the role of anions in bringing about the destabilization effect on collagen based on the kosmotropicity and chaotropicity of ions. Imidazolium-based ILs destabilized the triple helical structure of collagen, thereby proving as strong denaturants for collagen and this was confirmed by various spectroscopic techniques viz., CD, FT-IR, viscosity and impedance measurements. The solution studies were in accordance to the changes in the dimensional stability of RTT collagen fibres at the fibrillar level. Imidazolium cations with varied anions have exhibited destabilizing effect on collagen in order of ions in Hofmeister series; IDP < IDHP < IA < IDCA < IS < IHS. Presumably, these notable effect and changes were facilitated by electrostatic interactions between the anions and amine functional groups of collagen.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2019