Color enhancement of chrome tanned goat leathers using aqueous tea extracts as dyeing agent

This investigation was aimed at introducing natural dye extracted from the bark ofCassia Singueanaplant for dyeing chrome tanned sheep skin crust leather. The colorant was extracted by aqueous extraction and its strength evaluated using UV-Visible spectroscopy. The extraction with the highest strength (3.9 atλmaxof 400 nm) was obtained at temperature of 95°C, concentration of 60 g/l, and time of 60 minutes. The possibility of using aloe vera juice and mango bark extract as natural mordants for leather coloration was investigated. Dyeing was conducted with and without mordant using different combinations of temperature, time, pH, and concentration of mordants. All three mordanting techniques were evaluated. The color strength(K/S), CIEL⁎a⁎b⁎values, and fastness properties (light, rubbing, and perspiration) of dyed leather samples were evaluated using appropriate instruments and according to international standards. Majority of samples exhibited that fastness result was in the range of good-excellent. Significantly better color fastness was obtained in case of leather samples premordanted with aloe vera. This study leads to the conclusion that dye extracted from bark ofCassia singueanacan be used as colorant for tanned leather with the selected natural mordants.

UV-C irradiation critically effects the growth of micro-fungi and also deteriorate leather materials. In the present study vegetable tanned and chrome tanned leather were infected with pure cultures of Aspergillus niger and Aspergillus flavus, which were isolated from stored leather materials. UV-C light (λ = 254 nm) was applied on infected leather for 15 and 60 min. The changes in leather qualities were examined through weight, tensile strength, scanning electron microscope, energy dispersive X-ray and Fourier transform infrared spectroscopy study after 15 and 30 days of fungal inoculation. Vegetable tanned leather was more vulnerable in case of fungal attack than chrome tanned leather while A. flavus showed more influence on leather deterioration than A. niger. The results showed that weight loss after 30 days for 15 and 60 min irradiation exposure was 1.3% compared to A. flavus infected leather (3.93%). The tensile strength of vegetable and chrome tanned UV irradiated leather was increased by 44% and 7% respectively. The scanning electron microscopic images exhibit the limited presence of conidiophores in UV-C exposed leather which confirmed the potentiality of irradiation for controlling fungal growth. The infrared spectral analysis of UV-C exposed infected leather samples showed neither shifting of wavenumber nor displacement of any functional groups. Altogether the efficacy of UV-C irradiation against biodeterioration of leather was concluded to be effective. This method can be used to control fungal growth without compromising the leather quality.Graphical

Animal hides are one of man’s earliest and mostly used materials; many rawhide products, primarily leather, have for centuries been used for several purposes. The peculiar mechanical properties of leather depend on the hide composition, a dense collagen feltwork. Unfortunately, due to their proteic composition, rawhides may undergo microbial attack and biodeterioration. Over centuries, different processes and treatments (brining, vegetal or chrome tanning, tawing, etc.) were set up to face the biological attack and modify/stabilise the hide’s mechanical properties. Nevertheless, even present-day rawhides are subjected to biological colonisation, and traces of this colonisation are clearly shown in Chrome(III) tanned leathers (in the wet blue stage), with obvious economic damages. The colonisation traces on tanned leathers consist of isolated or coalescent red patches, known as red heat deterioration. Parchments are rawhide products, too; they derive from another manufacturing procedure. Even parchments undergo microbial attack; the parchment biodeterioration seems comparable to leather red heat deterioration and is known as purple spots. Recently, an ecological succession model explained the process of historical parchment purple spot deterioration; the haloarchaea Halobacterium salinarum is the pioneer organism triggering this attack. The marine salt used to prevent rawhide rotting is the carrier of haloarchaea colonisers (Migliore et al., 2019). The aim of this study was to investigate the dynamics of biodeterioration on Chrome(III) tanned leathers and its effects on the stability/integrity of collagen structure. To this end, standard cultivation methods were integrated with three updated technologies, Next-Generation Sequencing (NGS), Raman spectroscopy, and Light Transmitted Analysis (LTA). A bioinformatic comparison between chrome tanned leather vs. historical parchment colonisers was performed to evaluate if leather and parchment share common culprits; furthermore, the effect of the biodeterioration on the physical properties of the hide product was evaluated.

Tea is the second most commonly consumed beverage in the world after water. The leaf and bud of the plant Camellia sinensis produces tea. The different forms of tea are 'non-fermented' green tea, 'semi-fermented' oolong tea and 'fermented' black tea according to the manufacturing process. Streptococcus mutans is the main causative organism in dental caries and plaque formation. The present study was undertaken to determine the antibacterial effectiveness of aqueous and ethanol extracts of green tea, black tea and oolong tea against S. mutans in comparison with 0.2% chlorhexidine. An in vitro study was conducted to compare the effectiveness of aqueous and ethanol extracts of green tea, black tea and oolong tea with 0.2% chlorhexidine against S. mutans. Chlorhexidine 0.2% commercially available as mouthwash was used as such for comparison. The antimicrobial activity was determined using agar well diffusion method. About 50 µl of the aqueous and ethanol extracts of tea and 0.2% chlorhexidine were inoculated into the wells prepared on blood agar plates smeared with S. mutans. The agar plates were incubated for 24 hours after which the diameter of the zone of inhibition was measured. Analysis of Variance (ANOVA) followed by Tukey's post hoc test were used for statistical analysis. The mean zone of inhibition of the aqueous extracts of green tea, black tea, oolong tea and chlorhexidine was found to be 16.33 mm, 10.33 mm, 19.66 mm and 22 mm respectively. The mean zone of inhibition of the ethanol extracts of green tea, black tea, oolong tea and chlorhexidine was found to be 14 mm, 9 mm, 20.66 mm and 22 mm respectively. The study result state that the inhibitory effect of chlorhexidine is almost similar to that of oolong tea followed by green tea and black tea. From the present study, it can be concluded that the aqueous and ethanol extracts of oolong tea showed highest antimicrobial activity compared to green tea and black tea.

There are concerns that wearing chromium tanned leather gloves can provoke a lapse of hand dermatitis in chromium sensitive patients. Various forms of chromium have different biological effects and the determination of total chromium (both soluble and insoluble), which often is used in clinical studies, may therefore not be an adequate measure of the adverse exposure. However, investigations, where dissolution of hexavalent chromium from leather gloves has been experimentally studied, could not been found in the literature. The aim of this pilot study was therefore to determine the total amount of chromium and the amount of sweat leachable chromium in different leather glove materials and also to apply samples of these materials in a patch test to chromium sensitive patients to see if they could provoke a reaction. The results showed tha chromium tanned leather contained about 3% (m/m) chromium. Chromium can also be found in dyed vegetable tanned leather, probably emanating from the leather dye. Small amounts (average 0.08% m/m) of leachable hexavalent chromium were found in both chromium and vegetable tanned leathers. Thus, the risk of relapse of chromium dermatitis cannot be disregarded and further studies on the causes of relapse of chromium dermatitis are necessary.

Development of bio-acceptable leather using bagasse

Both natural and synthetic dyes have gained increasing attention in the leather dyeing process due to environmental and health considerations. This research was designed to determine and compare the antimicrobial efficacy of four natural dyes (Acacia catechu, Trema orientalis, Camellia sinensis, Swietenia macrophylla) with four synthetic dyes (brown BFR, brown NG, brown EDK, red G) to develop safer leather dyeing process. The above eight dyes were evaluated against eight prevalent pathogenic and opportunistic pathogenic bacteria Bacillus megaterium, Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Salmonella sp., Escherichia coli, Shigella sp., Pseudomonas aeruginosa, and four fungi. Dyestuff from Acacia catechu, Trema orientalis, and Swietenia macrophylla was effective against the three Bacillus strains, and Staphylococcus aureus with an inhibition zone extending from 6.3 mm to 11 mm. Synthetic dye brown BFR was effective against the three Bacillus strains, and Staphylococcus aureus with zone diameter of 14.8 mm to 19.7 mm. Brown EDK and Red G showed activity against Bacillus megaterium and Bacillus cereus. Camellia sinensis and brown NG showed no antimicrobial efficacy. Also, all eight dyes showed no antifungal activity. For both types of dyes, the zone of inhibition increased approximately linearly as dye concentrations increased. Of the natural dyes, Acacia catechu showed the highest activity. Brown BFR showed the maximum zone diameter of the eight dyes tested. The results indicated that both natural and synthetic dyes were quite effective. Synthetic dyes had remarkable antibacterial properties compared to natural dyes. These dyes having antimicrobial activity can be used in a safer leather dyeing process.

Biodegradability of leathers through anaerobic pathway

The extraction of natural dye using an aqueous method is a concept of green chemistry to avoid environmental pollution and toxicity. The present study was performed to improve the color strength and fastness properties of the fabrics by using natural dye and banana pseudo stem sap as a natural mordant. The natural dye was extracted from marigold flowers (Tagetes erecta) and optimized for dyeing of cotton and silk fabrics. The extraction of the dye was done in an aqueous solution without using any solvents. The optimum results were obtained when the fabric was dyed at 80°C for 60 min by keeping the mass to liquid ratio 1:40 at pH-7 (1.19). The color strength and CIELab (L*, a*, and b*) color parameters were also investigated. The effect of banana pseudo stem saps as a natural mordant on the color strength and fastness properties of the cotton and silk fabrics were evaluated and compared. The cotton fabrics were further characterized by FTIR spectroscopy and Scanning electron microscopy (SEM) to assess the physical and chemical changes after dyeing and mordanting.

Studies on the influence of bacterial collagenase in leather dyeing

The influence of particle size and extraction solvent on the antioxidant properties of aqueous and ethanolic extracts of tea (Camellia sinensis), ginger (Zingiber officinale), and tea–ginger (2:1) blend was investigated. The powder sizes studied were 0.425, 0.710, and 1.180 mm. Extracts were analyzed for DPPH radical scavenging activity, ABTS radical scavenging activity, total phenol content (TPC), iron chelating activity, total flavonoid content, and peroxide scavenging activity. The powder with the lowest particle size of 0.425 mm tends to produce aqueous extracts of tea, ginger, and tea–ginger with highest antioxidant content. At this lowest particle size all the antioxidant properties assayed were maximized. The TPC of aqueous extracts obtained from the 0.425 mm tea, ginger, and tea–ginger powders were 685.44 ± 175, 283.58 ± 19, and 483.02 ± 176 mg gallic acid equivalent (GAE) L−1, respectively. The TPC of aqueous extracts obtained from the 0.710 mm tea, ginger, and tea–ginger powders were 679.06 ± 169, 208.94 ± 147, and 400.10 ± 130 mg GAE L−1, respectively. However, for the aqueous ethanolic and ethanolic extracts, the particle size that maximized the antioxidant extraction varied depending on the antioxidant property that was being assayed. The study suggests that particle size influences the extraction of antioxidants. Also, the optimum powder size that would maximize antioxidant extraction is dependent on the solvent used and the antioxidant property being measured.

Temperature Regulation in Colored Infrared-Transparent Polyethylene Textiles

Evaluation of modified leather dyeing technique using black dyestuffs from the economical view

Objective: GABAergic system is a target for various groups of medications including sedatives, anxiolytics, muscle relaxants, antidepressants and antiepileptics. Several foods or food ingredients are able to affect the GABAergic system by the inhibition of the γ-aminobutyric acid (GABA) degrading enzymes including the GABA-transaminase and succinate semialdehyde dehydrogenase. The purpose of this study to investigate the inhibitory effects of tea (Camellia sinensis), coffee (Coffea arabica L.), peppermint (Mentha piperita L.), thyme (Thymus vulgaris L.), and cinnamon (Cinnamomum zeylanicum) on GABA degrading enzymes.Methods: The inhibition of the GABA-T by aqueous extracts of tea (Camellia sinensis), coffee (Coffea arabica L.), peppermint (Mentha piperita L.), cinnamon (Cinnamomum zeylanicum), and thyme (Thymus vulgaris L.) was investigated using a fluorometric microplate enzyme assay. Dose-dependent inhibition of the GABA-degrading enzymes was attained by all the food extracts tested. For determination of the IC50 values of the extracts (± 95 % CI), a linear regression was performed using Origin® (Origin® 2015G von Origin Lab Corporation, Northampton, MA 01060 USA).Results: The aqueous extract of black tea presented the strongest inhibitory activity with an IC50-value (half maximal inhibitory concentration) of 13.0 (11.0-15.3) µg/mL. The tested food extracts were successful in inhibiting the GABA-degrading enzymes even at low concentrations. Conclusion: In conclusion, the selected food extracts could serve as natural inhibitors for GABA-degrading enzymes thus, they could increase the GABA concentration in the brain.

Nitrosonaphthol dyes and other corresponding analogues were synthesised from 1-Naphthol. The dyes were applied onto chrome and vegetable tanned leather upon characterization. The results indicate that the dye bath exhaustion was better on chrome tanned leather than on vegetable tanned leather. This may be attributed to the chelating effect of chrome on leather and the higher temperature of dyeing the chrome tanned leather compared with the vegetable tanned leather. The fastness properties of the dyes of washing ranging from (3 - 5), perspiration on acid (4 - 5), alkaline (4 - 5) and light (4 - 7) were impressive on both vegetable and chrome tanned leather respectively.