Influence Of Tannins Research Articles

The influence of tannin on the improvement of adhesive properties of urea-formaldehyde resin

This study aimed to examine the properties of urea-formaldehyde (UF) adhesive with the addition of tannin, to determine whether it is possible to obtain so-called, bio-adhesives for wood with better mechanical properties compared to commercial UF. Tannin-based UF resins, with four different concentrations of tannin (5, 10, 15, and 20%), were prepared, and adhesive properties were tested and compared with properties of pure UF. Testing of tensile shear strength showed that the addition of tannin in UF adhesive formulation significantly increases its performance compared to pure UF adhesive. It was found that tensile shear strength increased with increasing concentration of tannin, while UF-tannin adhesives with tannin concentrations of 15% and 20% showed higher tensile shear strength than the corresponding pure UF adhesive. Therefore, it can be concluded that tannin-based UF adhesive can be a good candidate for application as an environmentally-friendly wood adhesive due to improvement in terms of adhesive and mechanical properties.

PSXIII-5 Behavior and blood urea nitrogen in cattle grazing meadow bromegrass and supplemented with condensed and hydrolizable tannins

Abstract The nutritional value of grasslands declines as the season progresses, negatively impacting cattle nutrition. Protein supplementation may reverse this trend, although high rates of ruminal proteolysis reduce the efficiency of N utilization. Tannins decrease protein degradability in the rumen, although they are also plant defenses with potential to influence animal behavior. The objective of this study was to determine in protein-supplemented cows grazing meadow bromegrass (MB) the influence of tannins on blood urea nitrogen (BUN), and on behavioral levels of activity. Twenty-four Black Angus cow [body weight (BW) = 614 ± 20 kg]-calf (BW = 244 ± 4 Kg) pairs were allotted to six 9-acre paddocks (4 pairs/paddock); animals in the Control (Ctrl; n = 3) and Tannin treatments (TT; n = 3) grazed meadow bromegrass (MB) and had a supplement of dried distillers grains with solubles (DDGS; (1 kgּ cow-1ּ d-1), with the addition of a mix of condensed (2/3): hydrolizable tannins(1/3; SilvaTeam) at 0.4% of the diet for TT. Grazing occurred from July to September 2023 with four experimental periods of 15 d each, the first being the adaptation period (no tannins; Baseline). Data were analyzed as a mixed-effects model with repeated measures and paddock as the experimental unit. Cows were fitted with accelerometers on their left back leg to determine activity, and blood samples were collected from all animals at the end of each period to estimate BUN. Representative samples of grass and supplement were collected from each period and paddock and analyzed for CP and fiber content. Herbage availability (DM basis) in each paddock was assessed before and post-grazing during each period using a rising plate meter and calibration curves. neutral detergent fiber (NDF) (62.9 to 65.1 ± 0.5%) and and acid detergent fiber (ADF) (38.7 to 43.9 ± 0.3%) increased, whereas CP (6.8 to 3.9 ± 0.1%) declined from Period 1 to 4 (P < 0.05). Initial biomass was 5,272 ± 211 Kg/ha and it declined after grazing (Period 4) to 2,319 ± 94 Kg/ha (P < 0.05) with no differences between treatments (P > 0.05). No differences between treatments were observed on motion index, number of steps taken per day, and the proportional percentage of time cows spent standing (9,379 ± 740, 2,611 ± 300, and 54.9 ± 0.02%, respectively; P > 0.05), suggesting that cows in TT did not invest extra time in searching activities or resting relative to Ctrl. It was only detected a greater percentage of transitions from lying to standing in TT than in Ctrl (7 to 3.4 ± 0.003%; P < 0.001). Values for BUN did not differ between treatments (P > 0.05), although they declined from Baseline to Period 4 by 28 % (8.2 to 5.9 ± 0.2mg/dL) in TT and by 2.6 % (5.75 to 5.6 ± 0.01 mg/dL) in Ctrl (P < 0.05). These results suggest that the addition of low levels of tannins to a protein supplement in cows grazing a low-quality grass diet reduces ruminal proteolysis without adversely influencing biomass removal or animals’ levels of activity.

Influence of tannin from Indian almond leaves on the curing behavior of Sucrose-Citric acid adhesive

The development of an eco-friendly wood adhesive composed of renewable materials has become a major topic of wood-based panel industry due to their safety for human health and potential use for particleboard production. Formaldehyde-based wood adhesive can emit formaldehyde which poses as a threat to the indoor air quality. Therefore, several researchers used sucrose, citric acid, and tannin as raw materials for the synthesis of eco-friendly adhesives, since these compounds showed a great synergy effect when used as a wood adhesive. A synthesized Citric-Sucrose-Tannin (CST) adhesives was studied in this work. Tannin, extracted from Indian almond leaves, was added into the 40 wt% of dry sucrose and citric acid in order to increase adhesion efficiency. To form the particleboard hot press is needed, each sample is pressed at temperature of 160 °C for three consecutive steps; four MPa for two minutes, two MPa for two minutes, and one MPa for two minutes. It was found that the optimized proportion of sucrose:citric:tannin in adhesive was 75/25/25 as it gave the particleboard the highest Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) values. Compared to non-adhesive particleboard, the MOR and MOE values were improved by two and four times when this formaldehyde-free adhesive was applied. It can be concluded that the eco-friendly wood adhesive composed of citric, sucrose, and tannin extracted from Indian almond leaves significantly enhanced both the mechanical and physical properties of particleboard.

Influence of tannin and iron ions on the water resistance of clay materials

The objective of this paper is to propose a simple and robust additive solution to improve the water-resistance of clay materials by revisiting a traditional recipe of vernacular construction. The influence of the combination of oak tannin with iron chloride on the properties of clay materials in terms of rheological behavior, compressive strength, and water resistance was studied. We show that adding iron chloride can annihilate the deflocculation action of tannin by a complexation reaction between iron ions and tannin. The accumulation and oxidation of formed complex at the sample surface, identified by TGA and SEM, prevent water ingression.

Influence of tannins and mannoproteins products on the improvement of organoleptic characteristics of wines

The aim of the work was to establish an influence of oenological tannins and mannoproteins products on the change of the organoleptic parameters of table dry wines, made from grapes of aromatic and non-aromatic varieties. The materials of the researches were wines that had defects or faults, mainly related with changes in wine aroma and taste. Oenological tannins of various botanical origins and mannoproteins products of a company Martin Vialatte (France) were used in the researches. Wines with these additives were mixed intensively, kept during 3 days at a temperature, not exceeding 12 °C and then determined the sensory characteristics of wine. Control samples were wines without additives. The descriptive method of analysis was used to create aromatic profiles of wines. The effectiveness of tannins and mannoproteins products on the sensory characteristics of wines was established. The intensity of the descriptors that made a positive affect on the aroma and taste of the samples was increasing. If, at the beginning tones of oxidation or bitterness were felt in the wines, then after introduction of the additives, these tones decreased in intensity. A difference of the changes of aromatic characteristics of wines from two groups of grapes with different aromatics was established. The action of additives was spread on the tings of descriptors, enriching the aroma of samples from non-aromatic grape varieties together with eliminating faults of taste. The effect of the additives was light in the aromatic varieties of grape that is due to the strong aroma and expressed taste of the grapes of these varieties. The results of the researches can be used to improve the quality of white wines, and further researches should be focused on the expansion of assortments of wines from other varieties, as a result utilizing tannins and mannoprotein products

Influence of tannins, human saliva, and the interaction between them on volatility of aroma compounds in a model wine.

During wine drinking, aroma release is mainly impacted by wine matrix compositions and oral physiological parameters. Notably, tannins in wine could interact with saliva protein to form aggregates which might also affect the volatility of volatiles. To explore tannins, saliva, and the interaction between them on the volatility of volatiles, the volatility of 16 aroma compounds in the model wine mixed with the commercial tannin extracts, human saliva, or both respectively, was evaluated in vitro static condition by using HS-SPME-GC/MS. The volatility of aroma compounds with high hydrophobicity or benzene ring appeared to decrease more when increasing the tannin levels. Specifically, the volatility of ethyl octanoate, β-ionone, and guaiacol was decreased more than 20% by adding 2 g/L tannin extract. The addition of human saliva could significantly inhibit volatility of most aroma compounds in the model wine. Furthermore, the volatility of most aroma compounds in the mixture of tannins and human saliva was significantly lower than the control or the sample which were added with tannins or human saliva individually. The volatility of some aroma compounds in the mixture of the tannin and saliva was only around 50% or less, relative to the control. Two-way ANOVA analysis showed that there was a synergistic effect between tannin and saliva on decreasing the volatility of most aroma compounds (p < 0.05). Overall, understanding the effect of key factors such as tannins and saliva on volatility of volatiles could help to understand the sophisticated retronasal perceptions during wine tasting. PRACTICAL APPLICATION: The outputs of this research will be helpful in understanding the impact of tannins on retronasal aroma release during wine tasting. It might promote the control of tannins in the viticulture and brewing process to improve the retronasal perception of wine aroma.

Response of the subtropical forest soil N transformations to tannin acid-organic nitrogen complexes

It is well known that the hydrolysable tannin (tannin acid) and condensed tannins in a plant can influence the availability of soil nitrogen (N) through the formation of tannin–organic N complexes. However, the lack of research on the effect of tannin acid–organic N complexes on soil N hinders our understanding of the subsequent role of these complexes. In this line, an incubation experiment was carried out with the addition of tannin acid-arginine and tannin-bovine serum albumin (BSA) complexes, where tannin acid was represented as the hydrolysable tannin. For the necessary comparisons, tannin acid, arginine, or BSA was added to the soil samples. The results showed that tannic acid addition quickly decreased protein contents at the beginning of incubation and decreased soluble organic N (SON) after 3 days to produce the inorganic N in the soil as compared to control. Tannin-arginine complexes increased NH4+–N compared with control and this increased degree was found lower than arginine treatment. Moreover, the addition of tannin–BSA complexes did not significantly increase soil NH4+–N as BSA alone treatment did. NO3−–N and N2O emission increased in each treatment compared with control indicating nitrification was not limited. The increase of NH4+–N was mainly attributed to the decrease of SON after 3 days of incubation. These results suggested that tannin acid quickly formed the complexes with protein to impact soil N. While, the effects of tannin-arginine and tannin–BSA complexes on soil N transformation were quite dissimilar. Thus, this study highlighted the subsequent role of tannin–organic N complexes under the influence of tannin. Tannin and tannin–organic N complexes naturally coexist in the ecosystem to impact soil N dynamics and may interact with each other as well.

Influence of tannin containing coatings on weathering resistance of wood: Combination with zinc and cerium oxide nanoparticles

In this study, influence of tannin containing coating combined with zinc and cerium oxide nanoparticles on color, gloss, surface roughness and macroscopic changes of Scots pine wood after artificial weathering was studied. For this purpose, 3 different tannin types, valex, mimosa and pine with various concentrations, 2 metal oxides, nano zinc and cerium oxide, and a water based transparent coating were used. Commercially available nano wood coating was used as a reference chemical. Results showed that wood surfaces got dark color, lost the initial gloss and become rougher after weathering of 1512h. Samples coated with tannin and nano metal oxide containing coatings exhibited better protection against degradation factors than reference and controls. Among the treatments, low concentration levels of tannins and cerium oxide were found to be more efficient on protection of wood surfaces in comparison to high concentration levels and zinc oxide. General condition of samples seemed to be better for mimosa and pine tannins for ZnO combinations, and valex and pine tannins for CeO2 combinations after the weathering test. Results of such a combination system clearly showed amount of expensive inorganic nanoparticles could be reduced with the addition of natural antioxidants into transparent coatings.

Influence of tannin containing coatings on weathering resistance of wood: Water based transparent and opaque coatings

The aim of this study was to improve weathering resistance of Scots pine wood by treating the surfaces with water based transparent and opaque wood coatings containing valex, mimosa and pine tannins. Samples coated with tannin containing coatings with various concentrations were exposed to artificial weathering for 1512 h. Color, gloss, surface roughness and macroscopic changes were evaluated periodically during the test, and the results of coated samples were compared with controls. Visible surface degradations such as erosion, cracks and checks occurred on control samples while no crack formations were recorded for coated samples. Color measurement data showed that high concentration levels were needed for the least color change on the surfaces however concentration increase of tannins in the transparent coating affected surface gloss and roughness of samples negatively. The most promising tannin types in transparent coatings against the surface degradations were determined as valex and pine tannins. Opaque coating alone was found to be resistant against weathering factors, and the measurements clearly showed that there is no need to corporate any UV absorbers to this coating.

In Vitro Ruminal Degradability of Soybean Meal Protein Protected with Natural Tannin

The influence of tannin from tea waste and gambier as natural tannin sources on ruminal protein degradability was studied in this investigation. The soybean meal was used as protein source in this investigation. There were three treatments in this investigation mainly without protection (NT); protection with tea waste (Tt); and protection with gambier (Tg). The measured parameters consisted of in vitro dry matter digestibility (IVDMD), in vitro organic matter digestibility (IVOMD), and the ruminal fermentation characteristics. Results of this experiment showed that protection with tannin from tea waste as well as gambier increased (p<0.05) the IVDMD (77.0 vs 85.10 and 86.20%) and IVOMD (75.70 vs 83.40 and 84.40%). The highest IVDMD and IVOMD (p<0.05) was found in Tg treatment group. The Ruminal Undegradable Protein (RUP) in Tt and Tg group was higher than that in NT group (66.29 and 69.20 vs 51.10%). The ruminal protozoa population decreased (p<0.05) as a result of tannin protection (6690 vs 3790 and 5480 microorganism/ml rumen fluid). The Tt treatment group showed the lowest (p<0.05) ruminal protozoa population. The ammonia concentration in Tt and Tg tend to be lower compared to NT (4.67 and 4.69 vs 5.00 mM). The soybean meal protein protection with tea waste and gambier tannin increased IVDMD, IVOMD, RUP. The ruminal protozoa population and ammonia concentration, on the other hand, were decreased by tannin protection from those tannin natural sources. The natural tannin from gambier was the most effective protection agent for soybean meal protein.

A low calorie and nutritive sorghum powdered drink mix: Influence of tannin on the sensorial and functional properties

Sorghum tannins are excellent antioxidants and may contribute to the health although their astringency is believed to be objectionable. This work aims to develop a low calorie and nutritive powdered drink mix with tannin-sorghum (PDT-3670) and tannin-free sorghum (PDTF-7064) extruded flours and to evaluate their sensorial, nutritional and functional properties. Both products were accepted on all attributes with acceptance from 70.9 to 93.2%. PDT-3670 had greater purchase intention than PDTF-7064 and better acceptability for flavor and overall acceptability. There was no difference in the aroma, texture and color acceptability between the two products. The antioxidant activity, phenols, tannins and anthocyanin contents were higher in the PDT-3670 powdered drink, having potential functional properties. Chemical analyzes indicated that both powdered formulates may be potential sources of fiber (7.9–9.1 g/100 g) and proteins (18.5 g/100 g). The serving size dissolved in water had 126.5–128.3 kcal and dissolved in milk 214–215.18 kcal. The tannin did not negatively influence the acceptance of drinks, and improved their functional properties. This nutritive and low calorie sorghum powdered drink mix has potential to be introduced, especially, into the gluten-free food market and can bring health benefits to the consumers.

Influence of tannin on aqueous layers at a surface of hydrophilic and hydrophobic nanosilicas

Pharmaceutical tannin was stirred with hydrophilic nanosilica A-300, hydrophobic nanosilica AM1 or their mixture (1:1). Tannin microparticles were strongly grinded during mechanical treatment with nanosilica to form much smaller tannin micro- and nanoparticles. The composites were studied with addition of water or acidic solution of HCl or F3CCOOD using low-temperature 1H NMR spectroscopy, NMR cryoporometry, microscopy, infrared spectroscopy, and quantum chemistry. Treated composites are characterized by reduced affinity toward water in comparison to hydrophilic A-300, but greater than that for initial tannin or hydrophobic AM1. The composites are characterized by increased mobility of organic molecules interacting with adsorbed water, acidic solution or chloroform. Consequently, grinded tannin can be more active in composites with nanosilicas than in the initial powder with microparticles. Chloroform affects location of bound water or acidic solution in voids between silica nanoparticles or weakly porous tannin particles because water and chloroform are practically immiscible and tend to reduce the contact area of one to another. Therefore, smaller water molecule can locate in narrow nanopores inaccessible for CDCl3 or in broad pores to form large domains. Upon location of a mixture of tannin with A-300/AM1 with bound water or acidic solution in the chloroform medium, hydrophobic AM1 nanoparticles can form a shell around hydrophilic A-300/tannin particles with bound water. In this case, contacts between bound water and chloroform can be minimal. Therefore, the system can be stable. This stability is higher for the composites with tannin than that for A-300/AM1 alone.

The influence of tannins on the human neutrophils' pro-inflammatory mediators

The influence of tannins on the human neutrophils' pro-inflammatory mediators

Hypotheses on the effects of enological tannins and total red wine phenolic compounds on Oenococcus oeni

Lot of articles report on the impact of polyphenols on wine lactic acid bacteria, but it is clear that the results still remain confusing, because the system is complicated both in term of chemical composition and of diversity of strains. In addition, red wines polyphenols are multiple, complex and reactive molecules. Moreover, the final composition of wine varies according to grape variety and to extraction during winemaking. Therefore it is nearly impossible to deduce their effects on bacteria from experiments in oversimplified conditions. In the present work, effect of tannins preparations, currently considered as possible technological adjuvants, was assessed on growth and malolactic fermentation for two malolactic starters. Experiments were conducted in a laboratory medium and in a white wine. Likewise, impact of total polyphenolic extracts obtained from different grape variety red wines was evaluated in the white wine as culture medium. As expected growth and activity of both strains were affected whatever the additions. Results suggest some interpretations to the observed impacts on bacterial populations. Influence of tannins should be, at least partly, due to redox potential change. Results on wine extracts show the need for investigating the bacterial metabolism of some galloylated molecules. Indeed, they should play on bacterial physiology and probably affect the sensory qualities of wines.

Effect of Ultrasonic-assisted Pretreatment on Hydrolysis and Fermentation of Acorn Starch

Acorn starch was used for ethanol production by separate hydrolysis and fermentation (SHF) in this study. The influence of tannins on hydrolysis and fermentation was investigated using ultrasonic-assisted extraction (UAE) to decrease the amount of tannin before SHF. The tannin was shown to have a negative role in hydrolysis and fermentation, and UAE can improve the two processes. The tannin content of acorn starch decreased from 6.19% to 1.91% with the UAE pretreatment time of 200 min. When the pretreatment time was 120 min, the glucose concentration increased from 78.08 to 98.76 g/L after 24 h of hydrolysis. The highest ethanol concentration was 42.22 g/L, which was obtained from the same pretreated acorn flour fermented for 12 h. However, the maximum ethanol yield was 88.06% of the theoretical yield, while pretreatment time was 80 min. Scanning electron microscope images indicated that protein was separated from the starch granules by UAE, as well as by the molecular weight of starch which decreased significantly based on the results from gel permeation chromatography (GPC) analysis.

Seasonal changes in nitrogen availability, and root and microbial uptake of 15N 13C 9-phenylalanine and 15N-ammonium in situ at a temperate heath

In the plant biosynthesis of secondary compounds, phenylalanine is a precursor of condensed tannins. Tannins are deposited into the soil in plant root exudates and dead plant material and have been suggested to precipitate some soil nutrients and hence reduce nutrient availability for plants. Free amino acid, inorganic and microbial N concentration during the growing season was investigated in an ecosystem with a natural tannin chemosphere. The influence of tannins on the uptake of nitrogen in plants and microbes was followed by injecting tannic acid (TA), ammonium- 15N and phenylalanine- 15N/ 13C 9. Plants preferred ammonium over phenylalanine, while microbes had no preference. Soil microbes had a 77% uptake of intact phenylalanine. Phenylalanine was acquired intact by both grasses and Calluna, with 63% and 38% uptake of intact phenylalanine in grass fine roots and Calluna roots, respectively. Inorganic N and amino acid concentrations were lowest in the period with highest plant activity and grass root biomass but were unaffected by TA addition.

Tannic acid and Norway spruce condensed tannins can precipitate various organic nitrogen compounds

Abstract There is increasing evidence that tannins affect degradation of soil organic matter and nitrogen cycling. It is assumed that the influence of tannins on biochemical processes is partly related to their ability to precipitate proteins. However, there is almost no information about precipitation of organic nitrogen-containing compounds other than proteins. A few studies indicate that tannins can precipitate arginine, choline or chitosan. In this study we used commercial tannic acid and condensed tannins extracted from Norway spruce (Picea abies (L.) Karst) needles to investigate precipitation of a wide range of organic nitrogen compounds including amino acids (all 20 proteinaceous), peptides (insulin, oxidized glutathion, reduced glutathion, AlaAla, GlyGlu, GlyPhe, GlyGlyGly), proteins (bovine serum albumin, Rubisco i.e. d -ribulose 1,5-diphosphate carboxylase), nitrogen bases, polyamines and aminosugars (N-acetyl- d -glucosamine, chitin and chitosan). Our results showed that tannins can precipitate a subset of these compounds – of the amino acids only arginine, of the peptides studied only insulin, all the proteins, polyamines, nitrogen bases, chitin and chitosan, but not N-acetyl- d -glucosamine. Concentrations of organic nitrogen compound and tannins affected amount of these compounds in precipitates. Moreover, pH value affected precipitation. The amount of precipitated organic nitrogen compound and the amount of precipitated tannins showed positive correlation across different pH. Precipitation of organic N-containing compounds other than protein by tannins can potentially affect reactions in all biochemical mixtures including tannins and these organic nitrogen compounds, and affect soil N cycling.

Polyphenol oxidase, tannase and proteolytic activity in relation to tannin concentration in the soil organic horizon under silver birch and Norway spruce

Our aim was to compare enzyme activities (tannase, polyphenol oxidase and protease) with concentrations of tannins and their ability to precipitate proteins in the litter layer and the humus layer under silver birch ( Betula pendula Roth.) and Norway spruce ( Picea abies L.). We also estimated the influence of these enzymes on protein–tannin complexes and the influence of tannins on proteolytic activity. The study site was a tree species experiment in Eno, middle-eastern Finland, having three replicated plots dominated by 42-year-old silver birch and Norway spruce. Our hypotheses were (1) tree species and soil layer have an influence on tannin concentrations and enzyme activities, (2) that tannin and protein concentrations in soil organic horizon are positively correlated with enzyme activities and (3) that the enzymes studied have the ability to degrade tannin–protein complexes and that tannins can inhibit proteolytic activity. Concentrations of total tannins and hydrolysable tannins, and tannase and proteolytic activities were higher in the humus layer than in the litter layer. In general the highest values of concentrations of total tannins and hydrolysable tannins and enzyme activities were obtained for the birch humus layer, but the concentrations of condensed tannins and proteins were highest in the litter layer and under spruce. A strong correlation between substrate concentration and enzyme activity was found between hydrolysable tannins and tannase activity. Polyphenol oxidase showed similar activities in both layers. To study the influence of enzymes on protein–tannin complex we synthesized such complexes using bovine serum albumin and either condensed tannins from silver birch and Norway spruce needles or a hydrolysable tannin, tannic acid. Studies with commercial enzymes and enzymes extracted from the soil showed some decrease in tannin concentration of the tannin–protein complex over time, but surprisingly, only a negligible decrease in protein concentration. Complexes of protein with condensed tannins were more recalcitrant than tannic acid–protein complexes. Tannins, depending on the concentration and chemical structure, tended to inhibit proteolytic activity. Our results indicate that protein–tannin complexes are relatively recalcitrant since the enzymes studied here do not effectively release protein from the complexes. Also proteolytic activity and the concentration of extractable proteins seem to be low in soil. However, tannin-degrading enzymes showed high activities.

Influence of Tannin on Dye Uptake and Wash Fastness at Dyeing of Silk Fabric with Amur Cork Tree

As the basic study to investigate the mechanism of improvement in the dyeing fastness of natural dyes on silk fabrics, the optical behavior of tannin solution, the optimal condition of tannin treatment and the changes of the physical structure of silk fabrics were studied in the treatment of tannin. As the tannin content of silk fabric was increased, the value of ξ-potential became negative. As the tannin content of silk fabric was increased, the crystallinity and crystallite size were decreased. The degree of orientation was also decreased with the tannin treatment. As the concentration of tannin was increased in its treating condition, the tannin content and K/S value of tannin-treated silk fabrics were increased. Because tannin gave rise to yellowing by hydrolysis and oxidation at high temperature, the higher tannin-treating temperature resulted in the lower the tannin content and K/S values of silk fabrics. The tannin content of silk fabric was higher in acidic treating condition and the highest K/S value was showed at pH 5. The optimum condition of tannin pre-treatment was 0.15% concentration, pH 4, 70°C, and 45min, and that of post-treatment was 0.05% concentration, 60°C, and 30min. The wash fastness and the light fastness were enhanced to 4 grades and 2~3 grades, respectively.

Characterization of condensed tannins from native legumes of the Brazilian northeastern semi-arid

Despite the possible influence of tannins on the nutritional value of the forages from Caatinga vegetation, there are few studies that evaluated their tannin concentration. This study was conducted to characterize condensed tannins present in the legumes species Mimosa hostilis (Jurema Preta), Mimosa caesalpinifolia (Sabiá) and Bauhinia cheilantha (Mororó), at three stages of their phenological cycle. The concentration of soluble tannin (ST), bound tannin (BT) and total tannin (TT) were determined using the butanol-HCL method; astringency was by the radial diffusion method, and the monomeric composition of purified tannins by a high-performance liquid chromatograph with delphinidin, cyanidin and pelargonidin as standards. Concentration and astringency of purified condensed tannins, as well as their monomeric composition varied between species, and in some cases among phenological cycles. The values observed were always above the limits considered beneficial for ruminal digestion (i.e. 5%). Jurema Preta presented the highest values (30.98% TT and 22% astringency at full growth stage), and Mororó the lowest (10.38% TT and 14% astringency during fructification). Jurema Preta presented a mean relationship prodelfinidin (PD): procyanidin (PC) of 97:3, which did not vary during the phenological cycle, showing the high astringent capacity of these tannins. Sabiá presented a relationship of 90:20 during full growth and flowering stages, decreasing to 40:50 at fructification. In Mororó the PD:PC relationship was more equilibrated, around 40:50 during full growth and flowering stages, decreasing to 35:60 During fructification. Propelargonidin was not detected or was present at low concentration in the three species.