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New Chrome Tanning Method Assisted by Wringing and Ultrasound 
by Jinwei Zhang, Yu Wang, Bo Teng and Wuyong Chen
Volume: 108      Number: 12     Page: 445-448     Year: 2013
A new chrome tanning method was designed using wringing (10 kg/cm2) and ultrasound (28 kHz, 300W). The grain down pickled skin was put into the penetration tank to let the chrome tanning agent penetrate for 3min. After penetration, the skin was transferred into the fixation tank to basify for 3min. Then the skin was again penetrated and fixated to finish the tanning process as is described above. During the penetration and fixation stage, an ultrasound field was used and the skin was transported with belts one by one. Before each stage skins were wrung to recover the penetration solution or fixation solution and lower the water content of the leathers to about 55%. The results showed that tanning time was obviously shorted compared with a conventional method because of the mechanical extrusion formation of the micro vacuum and ultrasonic cavitationsf effect. The wet blue obtained by the new method remained the same properties compared with conventional wet blue, such as shrinkage temperature, chrome content in leather, and physical properties after retanning, fatliquoring and finishing in a normal shoe upper leather process. Furthermore, collagen structure and cross section of the leathers maintained integrity during the tanning processCproved by SEM. In short, this new chrome tanning method assisted by wringing and ultrasound could be used in future tanning industry.
 
 
Treatment of Hides with Tara-modified Protein Products  
by M. Taylor, M. Medina, J. Lee, L. Bumanlag, N. Latona, E. Brown and C.-K. Liu
Volume: 108      Number: 12     Page: 438-444     Year: 2013
In prior research, we demonstrated that gelatin could be modified with quebracho to produce products whose physicochemical properties would enable them to be used effectively as fillers in leather processing, and that leather resulting from this treatment had improved subjective properties with little effect on mechanical properties. In an extension of the study, the tannin, tara was examined for its potential in gelatin modification. The advantage for using tara is that it gives an almost colorless product, which would be desirable in production of light colored leather, as well as imparting light fastness to the leather. The conditions for optimal tara modification of gelatin were determined and the products characterized. In this present study, these tara-modified gelatins were evaluated as fillers in the treatment of wet blue and wet white. In addition, the rate of uptake of the product was also examined using an analysis developed at ERRC for the measurement of polyphenols in foods. It was found that the treated leathers, when evaluated for their subjective properties (handle, fullness, break and color), demonstrated improved properties. There were no significant differences in treated and control samples of wet blue and wet white, with respect to the mechanical properties (tensile strength, elongation, Young’s Modulus, toughness index and tear strength). SEM examination of fiber structure showed differences in treated and untreated samples. Thus, another sustainable, economical resource, the polyphenolic tara, in conjunction with gelatin, has further shown its potential for use in leather production.
 
 
Characterization and Mechanism of Zinc Salts as Tanning Agents 
by Shan Cao, Baozhen Cheng, Qiaoe Wang and Bing Liu
Volume: 108      Number: 11     Page: 428-433     Year: 2013
Zinc has important biological functions as one of the essential trace elements to human. The Zinc tanning agent could produce white leathers with properties comparable to the chrome tanning agent, and the tanning agents based on Zinc salts were prepared using different masking agents such as sodium formate, sodium acetate, sodium tartarate and potassium hydrogen phthalate. The selection of the zinc tanning agents has been optimized based on the properties like hydrothermal stability and percentage exhaustion of zinc. The results indicated that zinc sulfate can be used as tanning agent under acidic conditions (50g/L, pH=3, 25Ž) and is an effective and superior method. Moreover, Sodium citrate (0.1mol/L) was selected as masking agent compared with other masking agents. The hydrothermal stability was improved effectively with the action of masking agent.
 
 
Characterization of the Volatile Organic Compounds by HS-SPME-CG-MS in the Leather Sector 
by R. Cuadros, A. Marsal, L. Olle, A. Bacardit and J. Font
Volume: 108      Number: 11     Page: 420-427     Year: 2013
Current European legislation demands a reduction in the amount of volatile organic compounds (VOCs) used in industrial processes. The presence of these compounds in the leather industry arises from the chemicals used in the various stages of the leather manufacturing process. An important aim of tanners is to reduce or eliminate VOCs, without lowering the quality of their leather products. The HS-SPME-GC-MS method is an innovation in leather analysis. The solid phase micro extraction (SPME) is a sample preparation technique used for the extraction of volatile and semi-volatile organic compounds and is becoming widely accepted as the technique of choice for many applications and that can be connected to gas chromatography. The main advantages of this technique are speed, sensitivity, and the fact that it requires no sample handling or solvent extraction. Other advantages include the fact that the concentration and the extraction are reached simultaneously and that it enables on-site extraction of the analyte, even without the prior destruction of the sample. This paper shows the development of a new HS-SPME-GC-MS method with a deuterated internal standard for the detection and identification of volatile organic compounds emitted by leather. This method enables us to carry out a simple and rapid determination of the qualitative and semi-quantitative composition of the organic compounds in the samples.
 
 
Analysis of Release of Free Formaldehyde Originated from THP Salt Tannages in Leather by High Performance Liquid Chromatography: Origanum onites Essential Oil as Free Formaldehyde Scavenger 
by E. Bayramoglu, A. Yorgancioglu and E. Onem
Volume: 108      Number: 11     Page: 411-419     Year: 2013
This study was about the release of free formaldehyde from tetrakis (hydroxymethyl) phosphonium (THP) salts and various syntan leather products, and the antioxidative blocking defense mechanisms of various essential oils. For that purpose, Citrus reticulata L., Melaleuca alternifolia, Origanum onites and Thymus vulgaris essential oils of 2% were used during fatliquoring. Formaldehyde analyses in finished leathers were performed according to TS EN ISO 17226-1 international standard by high performance liquid chromatography (HPLC) test method. To make a comparison on the analyses, some leather samples as a control group were processed without any essential oil. The results were evaluated statistically by using One-Way ANOVA and Duncan tests with the SPSS 15 statistic program. The results showed that Origanum onites essential oil used in fatliquoring process was significantly determined to eliminate the release of free formaldehyde in leather.
 
 
A Novel Chromium-free Tanning Process Based on In-situ Melamine-formaldehyde Oligomer Condensate 
by Xue Bai, Jinming Chang, Yi Chen, Haojun Fan and Bi Shi
Volume: 108      Number: 11     Page: 404-410     Year: 2013
To manage the environmental impacts of chrome tannage, a burgeoning option lies in seeking alternatives that reproduce the high hydrothermal stability and retain the versatility of chromium salts. In this study, a novel chromium-free tanning process based on in-situ condensate melamine-formaldehyde oligomer was reported. Instead of using prepared melamine-formaldehyde syntan, which inevitably contained post-condensates with compromised penetration capability and reactivity, melamine and formaldehyde monomers were first allowed to penetrate evenly into bated hides and then condensation was triggered in-situ. Total organic carbon (TOC), total nitrogen (TN), Fourier transform infrared (FTIR), and isoelectric point (IP) analysis demonstrated these in-situ condensate oligomers covalently reacted with amino or hydroxyl residues, introducing rigid and stable chemical crosslink between collagen chains. Consequently, the hydrothermal stability of the tanned leather was significantly enhanced, evidenced by thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and a shrinking temperature (Ts) approaching 93 oC. In addition, scanning electron microscope (SEM) observation indicated that the in-situ tanned leather exhibited smoother grain, more even and much looser fiber structure compared with control, which was tanned by traditional melamine-formaldehyde syntan. According to these results, the in-situ condensation strategy developed in this study could be employed as an efficient chromium-free tannage, which eliminated the adverse effects of post-condensates in traditional melamine-formaldehyde syntan while exhibiting improved tanning efficiency.
 
 
Collagen Modification using Nanotechnologies: A Review 
by Dang-ge Gao, Jian-Zhong Ma, Bin Lv and Jing Zhang
Volume: 108      Number: 10     Page: 392-400     Year: 2013
The essence of leather the industry is modified collagen fibers. With more challenges facing traditional chemicals used for leather making, along with the development of higher living standards, great demand is imposed on the leather industry. Therefore, more researchers are paying attention to collagen modification using nanotechnologies for the leather industry. In this review, we present a critical discussion of collagen modified by nano-size emulsion, clay minerals, nano silicon dioxide, or nanosilver. In the end, we conclude this review with some perspectives on the future research and development of collagen modified by nanotechnology.
 
 
Low Carbon Products for the Design of Innovative Leather Processes. Part I: Determination of the Optimal Chemical Modificatoin of Tara 
by A. Bacardit, C. Casa, J. Diaz, R. Cuadros and L. Olle
Volume: 108      Number: 10     Page: 386-391     Year: 2013
This study considers the fruit of the tara bush as a sustainable source of tanning agents and proposes alternatives to the mineral salts and vegetable extracts for commercial use. Specifically, in part I of the study various processes of physical and chemical modification were developed in order to obtain a modified tara with a higher percentage of tannins which can therefore improve their tanning capability. Several aqueous extraction processes at different temperatures were developed and optimized in order to decrease the astringency and facilitate the penetration of the tannin molecules through the leather structure. RESUMEN Este estudio considera el fruto del arbusto tara como fuente sostenible de agentes curtientes y propone alternativas a las sales minerales y extractos vegetales para uso comercial. Específicamente, en la parte I del estudio diversos procesos de modificación física y química se han desarrollado con el fin de obtener una tara modificada con un mayor porcentaje de taninos que permita mejorar su capacidad de curtido. Varios procesos de extracción acuosa a diferentes temperaturas se han desarrollado y optimizado con el fin de disminuir la astringencia y facilitar la penetración de las moléculas de tanino a través de la estructura de cuero.
 
 
Synergistic Effect of Direct and Alternating Electric Current Treatments and Bronopol to Inactivate Bacteria Found in Hide Soak Liquors 
by Y. Birbir, N.Dolek, M. Birbir and P. Caglayan
Volume: 108      Number: 10     Page: 373-385     Year: 2013
It is well known that bacteria on hides and in the hide-soak liquors do damage that compromises leather quality. These harmful bacteria are resistant to the antibacterial agents used in the hide industry. In this research the synergistic effect of a combined electric current treatment using both 1.5 A direct and 2.0 A alternating electric currents, followed by 1 g/L of bronopol treatment on mixed culture of Gram positive and Gram negative hide bacteria was examined in a liquid medium containing 2% NaCl and organic substances. Enterobacter cloacae, Vibrio fluvialis, Pseudomonas luteola, Staphylococcus cohnii, Enterococcus faecium and Bacillus pumilus were used as test isolates. Six different experiments were carried out on the mixed culture of test bacteria to determine the efficiency of the synergistic effect of a combined electric current treatment. Bacterial cell counts were reduced to low level in a short period using the electric treatment. More than 2 log reduction factor of the mix culture was observed within 12 min after the electric current treatment, and the damaged bacteria were killed easily by bronopol in five hours. DC and AC electric currents in combination with antimicrobial agents may be used to more efficiently exterminate the bacteria found in the hide-soak liquors. RESUMEN Es bien conocido que las bacterias en las pieles y en los licores de remojo provocan daños que comprometen la calidad del cuero. Estas bacterias dañinas son resistentes a los agentes antibacterianos utilizados en la industria de la piel. En esta investigación el efecto sinérgico de un tratamiento combinado de corriente eléctrica utilizando ambas corrientes eléctricas, 1.5A contínua y 2,0A alterna, seguido de 1 g/l de tratamiento con bronopol en cultivo mixto de bacterias Gram positivas y Gram negativas se examinó en un medio líquido que contiene 2% de NaCl y sustancias orgánicas. Enterobacter cloacae, Vibrio fluvialis, Pseudomonas luteola, Staphylococcus cohnii, Enterococcus faecium y Bacillus pumilus se utilizaron como cepas de prueba. Seis diferentes experimentos se llevaron a cabo en el cultivo mixto de bacterias de prueba para determinar la eficiencia del efecto sinérgico de un tratamiento combinado de corriente eléctrica. Los recuentos de células bacterianas fueron reducidos a un nivel bajo en un corto período de tiempo con el tratamiento eléctrico. Se observó más de 2 factores de reducción logarítmica de la cultura de la mezcla dentro de los 12 minutos posteriores al tratamiento con corriente eléctrica, y las bacterias dañadas murieron fácilmente por bronopol en cinco horas. Corrientes eléctricas contínuas y alternas en combinación con agentes antimicrobianos pueden ser utilizados de manera más eficiente para exterminar las bacterias que se encuentran en los licores de remojo.
 
 
Biochemical Method for Extraction and Reuse of Protein and Chromium from Chrome Leather Shavings: A Waste to Wealth Approach 
by A. Pati, R. Chaudhary and S. Subramani
Volume: 108      Number: 10     Page: 365-372     Year: 2013
Chrome shavings are one of the major solid wastes generated during the leather making process. The presence of chromium in waste creates difficulty in disposing to landfill and incineration. Growing environmental concern about the toxicity and environmental impact of the chromium solid waste generated from the tannery has become key issue. In this work, a study has been made to extract protein from chrome shavings through a biochemical method. In this biochemical method the combination of chemical and enzyme processes have been employed to achieve the optimum extraction of protein. Optimization studies on enzyme and alkali concentration, time, pH and temperature on protein extraction were performed. Further, protein extraction by protease mixed with ¦Á-amylase has also been investigated. It was found that there was significant change in the protein extraction by protease in the presence of ¦Á-amylase. The protein extraction efficiency by conventional and biochemical method is found to be 60 and 80%, respectively. This study provides a biochemical method of hydrolysis for chrome shavings to protein and chromium. RESUMEN Las virutas de cromo son uno de los principales residuos s¨®lidos generados durante el proceso de fabricaci¨®n de cuero. La presencia de cromo en los residuos crea dificultades en la disposici¨®n en vertederos y su incineraci¨®n. La creciente preocupaci¨®n medioambiental acerca de la toxicidad y del impacto medioambiental de los residuos s¨®lidos de cromo generada a partir de la curtiembre se ha convertido en tema clave. En este trabajo, se ha hecho un estudio para extraer prote¨ªna a partir de virutas de cromo a trav¨¦s de un m¨¦todo bioqu¨ªmico. En este m¨¦todo bioqu¨ªmico la combinaci¨®n de procesos qu¨ªmicos y enzimas se han empleado para lograr la extracci¨®n ¨®ptima de la prote¨ªna. Se realizaron estudios de optimizaci¨®n de la enzima y la concentraci¨®n del ¨¢lcali, tiempo, pH y la temperatura de extracci¨®n de la prote¨ªna. Adem¨¢s, la extracci¨®n de prote¨ªnas mediante proteasa mezclada con ¦Á-amilasa tambi¨¦n ha sido investigada. Se encontr¨® que hubo cambio significativo en la extracci¨®n de prote¨ªnas por la proteasa en presencia de ¦Á-amilasa. La eficiencia de la extracci¨®n de prote¨ªnas por el m¨¦todo convencional y bioqu¨ªmico fue de 60 y 80%, respectivamente. Este estudio proporciona un m¨¦todo bioqu¨ªmico de hidr¨®lisis de virutas de cromo hacia prote¨ªna y cromo.