Commercial Tannin Research Articles

PSXII-24 Use of a commercial blend of tannins as feed additive for feed lot cattle on large pen trial improves carcass weight and carcass feed conversion

Abstract The utilization of commercial tannin extracts as feed additives holds promise for enhancing animal performance and health within commercial feedlot settings. This study aimed to assess the impact of a commercial tannin blend, SilvaFeed BX (Indunor, Buenos Aires, Argentina), sourced from quebracho and chestnut extracts along with saponins, on the performance of beef cattle. Nelore bullocks (n = 1,198) were allocated to 12 pens in a completely randomized block design, stratified by initial date, at a commercial feedlot facility in Goias State, Brazil. Each pen served as an experimental unit, with 10 pens housing 100 animals each and 2 pens containing 99 animals each. The experimental treatments included a Control diet with monensin alone [25 ppm/kg dry matter (DM)] or treated with BX (0.7 g/kg DM) on top of the control diet. Individual body weights (BW) were recorded at processing (initial BW; IBW) and shipment (final BW; FBW), while DM intake (DMI) was averaged per pen throughout the study duration. Carcass weight (CW) was individually measured at the packing plant, and carcass gain was calculated as the discrepancy between carcass weight and the estimated initial carcass weight, set at 50% of the IBW, aligning with customary practices for negotiating feeder cattle in Brazil. Statistical analyses were conducted using Proc Glimmix in SAS, treating pens and treatments as fixed effects and blocks as random effects, with IBW considered as a covariate. Residuals were assessed for normality, identifying three outliers. Mean comparisons were facilitated using LSMEANS. The results indicated that BX-treated cattle exhibited increased FBW (502.17 vs. 493.64 kg, P = 0.0992), carcass weight (275.76 vs. 268.78 kg, P = 0.0343), total carcass gain (107.52 vs. 100.54 kg, P = 0.0343), and improved carcass feed conversion (10.46 vs. 11.45 kg DM/kg; Table). Despite numerical differences, the limited number of replications were not enough to detect significant differences between treatments in average daily gain (P = 0.2419), DMI (P = 0.5508), feed conversion (P = 0.2641), or dressing (P = 0.3757). In conclusion, BX, a blend of tannins, exhibits potential for enhancing carcass weight and feed conversion efficiency in Nelore bullocks. Further investigations employing larger sample sizes are warranted to comprehensively elucidate its effects on other performance parameters.

Cationic tannins as aggregation agents in the flocculation on hematite–silica system

ABSTRACT This study aims to evaluate the use of commercial tannin derivatives, namely, tannin 1 (CT1), tannin 2 (CT2), tannin 3 (CT3), and extract of tannin produced from angico bark, as aggregation agent in hematite–silica systems. Hematite and quartz were used in aggregation tests at dosages of 1, 10, and 100 mg/L at pH values of 6–9. The zeta potential and Jar tests were conducted in the best conditions of aggregation tests. The condensed tannin content of the commercial reagents is approximately similar, and it exceeds the content found in the extract obtained from angico bark. CT3 demonstrated superior percentages of sedimented material for both minerals at a dosage of 10 mg/L and pH 7 (97.12% and 95.68% for hematite and quartz, respectively). The aggregation agent produced from the angico bark displayed good sedimentation results for hematite (>90%); however, the results for quartz were unsatisfactory. The isoelectric point shifts to pH 8 when each mineral was conditioned with CT3. The jar test revealed higher sedimentation of the compositions for the lowest velocity gradient (60 rpm) with low turbidity values in the supernatant; however, the lowest turbidity (24.71 NTU) is observed in the sample with a higher percentage of hematite.

Tannin impregnation pre-treatment of potatoes as a valuable strategy for acrylamide, monochloropropanediol and glycidol mitigation in chips and frying oil

This study focused on evaluating the mitigating effect of five different natural extracts of commercial tannins on the concentration of food contaminants such as acrylamide (AA), glycidols (GD), and monochloropropanediols (MCPDs) in potato chips and frying oils after the impregnation of potatoes with tannins. The impregnated samples were used to perform 4 consecutive fryings to simulate the effect produced in restaurants. AA mitigation was achieved in all pre-treated chips throughout the four frying cycles (except for the chestnut extract). The highest AA mitigation (86.6%) was achieved using quebracho extract. This correlated positively with the progress of Maillard reaction measured at 284 nm. In potato chips, 3-MCPD and GD were decreased by most tannins tested, whereas 2-MCPD was only mitigated using hydrolyzable tannins. However, in frying oils, 3-MCPD showed a decrease using chestnut, grape seed and quebracho extracts, 2-MCPD decreased using all tannins, and no effect was observed on GD. To our knowledge, this is the first study using tannins as a mitigation strategy to decrease MCPDs and GD; and it seems a good approach to keep low concentrations of these compounds. Indeed, hydrolyzable tannins seem the best option to mitigate MCPD and GD and condensed tannins the best one to mitigate AA.

Exploring the potential of tannin-rich tree bark extracts in combating foodborne diseases and gastric cancer

The objective of this study was to perform chemical characterization of tannin-rich extracts obtained from the bark of woody species and to assess their bioactive potential for the treatment of foodborne diseases and gastric cancer. The barks of Anacardium occidentale, Stryphnodendron adstringens, and a commercial tannin from Acacia mearnsii were used to prepare the extracts. HPLC was employed to determine the profile and quantity of phenolic compounds present in the extracts, while FTIR was utilized to identify their functional groups. The antioxidant activity was assessed using the DPPH assay, while the antimicrobial activity was evaluated by the disk diffusion method and measurement of minimum inhibitory concentration and minimum bactericidal concentration. Additionally, the antitumor activity was evaluated using the MTT-tetrazolium assay. The phenolic profile of the extracts revealed the presence of ten compounds, with gallic acid and catechin being the most abundant for all species. Hydroxyl (OH) was the recurrent functional group in all the analyzed extracts. At a concentration of 25 μg/mL, the extracts exhibited DPPH free radical scavenging activity of 90%. The extracts had significant antitumor potential, inhibiting the growth of human gastric adenocarcinoma cells (AGS) by 90% at 200 μg/mL. Listeria monocytogenes was the most sensitive bacterium to the use of the extracts, while Escherichia coli was the most resistant. In conclusion, the results obtained in this study demonstrated the promising potential of tannin-rich extracts from the studied species as antioxidant, antimicrobial, and anticancer agents.

The Influence of Tannins, Saponins, and Direct Fed Microbials on In Vitro Rumen Fermentation Characteristics and Microbiota

In-vitro experiments were conducted to determine the impact of tannins, saponins, and DirectFed-Microbials (DFM) on rumen fermentation characteristics. Rumen fluid was collected 2h post feeding from three cannulated crossbred (Angus x Hereford) feedlot steers (450±12.2 kg), adjusted to finishing diet. Rumen fluid from all steers were filtered, combined, and mixed with buffer. Vaccine bottles containing ground finishing diet and appropriate treatments were incubated with rumen fluid mixture (39 ˚C). Treatments consisted of 1) Control; 2) Commercial Tannin (TCH); 3) Hydrolysable Tannin (HT); 4) saponin; 5) TCH+DFM; 6) HT+DFM; and 7) Saponin+DFM. At 12 h post incubation, HT+DFM and Saponin+DFM had lesser (P<0.05) molar proportions of acetic acid when compared to all other treatments. Saponin+DFM had greater (P<0.05) molar proportions of propionic acid and a lesser (P<0.05) acetate: propionate ratio when compared to treatments not containing DFM. Dry matter digestibility and pH were greater (P<0.05) for saponin, TCH+DFM, HT+DFM and saponin+DFM, whereas pH was greater in treatments containing DFM compared to the controls. Percent CO2 was lesser (P<0.05) in saponin and THC+DFM in vitro vessels compared to controls. At 18 h post fermentation total VFA concentrations, molar proportions of butyric and valeric acid, and gas cap N2 percentage were greater (P<0.05) in in vitro vessels containing HT+DFM compared to controls. The percentage of CO2 was lesser in in vitro vessels containing HT compared to control and in vitro vessels containing saponin, HT+DFM and Saponin+DFM. At 12 h, alpha and beta diversity of the microbial community between treatments differed (P<0.05). Across all samplesat 18 h of fermentation the genera Sharpea and Dialister were present, however Saponin+DFM and TCH+DFM treatments demonstrated the greatest relative abundance. While Sharpea contribute to rumen biohydrogenation, the presence of genus Dialister indicates association with energy harvesting bacteria and suggests that the inclusion of several of these feed additives allowed shifts of certain bacteria to occur.

On-Farm Methane Mitigation and Animal Health Assessment of a Commercially Available Tannin Supplement in Organic Dairy Heifers.

The objective of this experiment was to demonstrate the effectiveness of a commercially available tannin product (Silvafeed® ByPro, 70% tannic acid) as an enteric methane (CH4) mitigation and preventative animal health strategy in Holstein heifers (BW = 219 ± 17 kg; 9 mo), reared under organic production system requirements. Twenty heifers were randomly assigned to one of four commercial tannin supplementation treatments as follows: 0% (0 g/hd/d; CON), 0.075% (~5 g/hd/d; LOW), 0.15% (~10 g/hd/d; MED), and 0.30% (~21 g/hd/d; HIG) of dry matter intake (DMI). Heifers received their treatment in individual animal feeding stanchions and were fed a basal total mixed ration (TMR) through four SmartFeed Pro intake measurement bunk systems (C-Lock Inc., Rapid City, SD, USA) for 45 d. An automatic head chamber system (AHCS; i.e., GreenFeed, C-Lock Inc., Rapid City, SD, USA) was used to continuously evaluate enteric CH4 production. No effect was observed among the treatments for CH4 emissions (p ≥ 0.55), animal performance (p ≥ 0.38), or oxidative stress biomarker concentration (p ≥ 0.55). Superoxide dismutase (SOD) and reduced glutathione (GSH) concentrations exhibited a linear response to increasing tannin dose (p = 0.003), indicating a potential tannin effect on the antioxidant status of dairy heifers. This observation may encourage future tannin research relating to animal health, which may be of particular interest to organic dairy systems. The results of this study suggest that tannin supplementation at 0%, 0.075%, 0.15%, and 0.30% of DMI, did not alter CH4 emissions, animal performance, or oxidative stress biomarker concentration in organic Holstein heifers when assessed under an on-farm research approach. Further, the results of this study affirm the challenges associated with on-farm research and the development of climate-smart strategies that are capable of mitigating climate impacts in less controlled environments under standard working conditions.

Digestibility and nitrogen balance of goats on high and low protein rations supplemented with a commercial tannin feed-additive

ABSTRACTDespite the increasing importance of goat production in response to high demand for their products and their relative robustness to environmental stressors, and in contrast to other ruminant species, little data is available on how tannin extract feeding affects their feed intake, nutrient digestion and nitrogen (N) metabolism. Therefore, a trial in Oman investigated the respective variables by using a commercial tannin feed additive. In a 4 (treatments) x 3 (periods) x 2 (animals) Youden square, two weaned Batinah bucks each were fed a high or low protein diet of Rhodes grass hay and crushed barley grain, with or without the addition of a chestnut and quebracho tannin extract at 2 g/kg metabolic weight. Feed offered, feed refused and faeces and urine excreted were quantified to determine diet digestibility, total N excretion, N retention and rumen microbial protein synthesis (MPS). Due to their young age and low live weight, feed intake of goats was relatively low. Crude protein level and tannin addition had no statistically significant effect on dry matter (DM) and N intake, DM digestibility, N excretion in faeces and urine, as well as MPS. In consequence, no benefit of tannin feeding could be confirmed for the goats’ N retention, irrespective of diet composition. These results indicate, on one hand, an effective neutralisation of the tested tannin extract along the gastrointestinal tract of goats, but on the other hand, that stimulation of MPS or N retention by tannins cannot be evidenced when diet components are present that simultaneously release energy and protein, as is the case with barley.

New Insight on the Formation of 2-Aminoacetophenone in White Wines

This study aimed to improve the understanding of 2-aminoacetophenone (2-AAP) formation in white wines, a compound responsible for atypical ageing (ATA) associated with a rapid loss of white wine fruity aroma and to the development of unpleasant odors. Two surveys performed in 139 white wines from Central Europe investigated the varietal effect on wine tendency to form 2-AAP during ageing. The role of some antioxidants and important transition metal ions present in wine (Fe, Cu and Mn) in the formation of 2-AAP was also investigated. The surveys highlighted that Muscat and Riesling wines showed significantly higher concentrations of 2-AAP than Chardonnay and some other regional varieties found in Central Europe such as Grüner Veltliner, Welschriesling and Zelen. The origin of such varietal effects could not be related to the level of any 2-AAP precursor. On the other hand, some of the important wine matrix effects were highlighted. A certain variability in capacity of different antioxidants to limit 2-AAP formation was observed. Supplementations of commercial tannins in wines tended to be more efficient than glutathione in preserving wines from the formation of 2-AAP. Transition metal ions significantly impacted 2-AAP synthesis through complex interactions. Generally, Fe and Mn tended to promote formation of 2-AAP, while the presence of Cu limited it. The higher concentration of transition metal ions significantly improved the efficiency of antioxidants to reduce 2-AAP formation. Further studies investigating the origin of varietal effects and the complex matrix effects involving metal ions and antioxidants in 2-AAP production are warranted.

Effect of commercial tannins on parasitic infection and immunity of lambs naturally infected with Haemonchus contortus.

This study aimed to evaluate the effects of different doses of quebracho extract tannins (Schinopsis lorenzii) (EQ) included in the basal diet (DB) on the count of eggs per gram of feces (EPG), count of parasites in the abomasum, hematological, and immunological parameters in lambs naturally infected with Haemonchus contortus. Forty-eight lambs were evaluated for 42days and divided into four groups (n=12): CONT- lambs that received DB without EQ supplementation; G1%- DB with EQ at 1% of dry matter intake (DMI) level; G3%- DB with EQ at the 3% of DMI level; G6%- DB with EQ at the 6% DMI level. For EPG counts, feces were collected weekly. For counting abomasal parasites, at the end of the experiment (D42) half of the lambs in each group were slaughtered. For hematological and immunological analysis, venous blood samples were collected at D0, D21, and D42 to perform the erythrocyte count, mean cell volume (MCV), hematocrit, differential leukocyte count, total plasma protein dosage, and serum IgA class anti-H. contortus using an indirect enzyme immunoassay (ELISA). In the EPG count, there was no significant difference (p>0.05) between the groups compared with the control. Analysis of the abomasal parasite count showed Haemonchus contortus in its entirety; however, there was no significant difference (p>0.05) in the number of males, females, and total parasites. No differences (p>0.05) were observed in erythrocyte count, MCV, hematocrit, and total plasma protein. The average total leukocyte, monocyte, eosinophil, and basophil counts showed no difference (p>0.05). However, the averages of segmented neutrophils in the G1% and G3% groups presented a reduction in the percentage of cells (p<0.05) between D21 and D42. Regarding the lymphocyte count, a difference was observed in the CONT and G3% groups at D21 and D42 (p<0.05), when compared to D0. The analyses of the average absorbance of anti-Haemonchus contortus serum IgA showed no difference (p>0.05), when the groups were analyzed over time or when compared between them. It can be concluded that the inclusion of different doses of tannins from EQ did not alter the parasitological, hematological, and immunological parameters of lambs infected with H. contortus.

Appropriateness of Anogessus leiocarpus leaves and bark as vegetable tannins traditionally used in leather making in Sudan

Chrome tanning industry is dominated globally owing to its high versatility in quality leather production. However, Environmental impacts of chromium have shifted the interest of present study to chrome-free options. Vegetable tannins have been proven to be environmentally safe producing good quality leather with comparable properties as that of chrome tanned leather. As such, scarcity of vegetable tannin supply demands characterization of non-commercialized sources locally available to feed local tanners. A simple extraction technique was used with different temperature 35, 50, &amp; 85 oC. Leaves and barks from Anogessus leiocarpus grown in Sudan can produce commercially acceptable tannins in terms of extract yield, tannin, total phenolic, flavonoid contents, and crosslinking ability comparable to the extract from A. mearnsii barks, which is a worldwide known to be commercial tannin source. Results shows that temperature influences on extraction yields and tannin content was low, except for extract from Anogessus leiocarpus leaves that has shown an increase pattern with raise in temperature. Total phenolic and flavonoid content varied insignificantly with increase in extraction temperature, except for total flavonoid content of extract from Anogessus leiocarpus leaves that observed to be high at 50 oC (30.7). Variations in extract properties between extracts from plant parts studied in this work were significant. Tensile strength values of tanned skin with leaves extracts are higher than that tanned with barks. On the other hand, tanned skin with leaves extract produced greater skin elongation 40.6±0.35 compared to barks extract.

Evaluation of oenological tannins for preventing the light-struck taste

The light-struck taste (LST) is a fault occurring in white and rosé wines associated to the formation of volatile sulfur compounds (VSCs) due to the reactions between riboflavin (RF) and methionine (Met). We investigated the possible preventing effect of 15 commercial tannins of different origin in model wine added with RF and Met, under oxic and anoxic conditions, and submitted to standardized light-exposure. All the tannins limited the degradation of Met in comparison to the tannin-free samples. Lower concentrations of VSCs were found in presence of tannins even under anoxia, condition favouring their formation. The sniffing trials evidenced the minor perception of cooked cabbage note with added tannins. The multivariate analysis showed the presence of flavan-3-ols was related to the formation of DMDS and DMTS, while tannic acid was related to MeSH, both the behaviors occurring under oxic condition. The study highlighted the ability of tannins to prevent the LST.

Tannin-rich tree bark extracts inhibit the development of bacteria associated with bovine mastitis

Condensed tannins were quantified in the barks of selected tree species, and the antibacterial activity of these substances against clinical and subclinical isolates of bovine mastitis were evaluated. Tree barks from Mimosa tenuiflora, Mimosa caesalpiniifolia, Anacardium occidentale, and Stryphnodendron adstringens were used, as well as commercial tannin from Acacia mearnsii. The tannins were extracted using a mixture of ethyl alcohol and acetone. The moisture content (MC), Stiasny index (SI), total solids content (TSC), and condensed tannins (CT) were measured. The evaluation of antimicrobial activity was determined by applying the disk diffusion test. The species that showed the highest CT were M. tenuiflora and A. occidentale, with 37.3% and 37.3%, respectively. The highest SI were obtained by the species A. occidentale and M. caesalpiniifolia, with values above 90%. The bacterium with the lowest resistance to the use of tannins was Streptococcus uberis. A. mearnsii was the only one capable of inhibiting the growth of Escherichia coli, with a mean inhibition halo of 9 mm. All species under study showed high values of condensed tannins in their barks. In addition to showing good performance as antimicrobial agents, these tannins indicated potential applications in the development of natural medicines for the treatment of bovine mastitis.

Long-term study on the nitrogen retention potential of bark extracts and a polymer based thereof in cattle manure slurry

The addition of tree bark extracts, commercial tannin powder and a tannin-based polymer to cattle manure was investigated for its influence on the gaseous emission and nitrogen conservation potential for 28 days. In lab trials with ammonia solution as reference, the retention of ammonia was 13%, 40% and up to 65% for untreated solution, spruce bark extract and chestnut tannin respectively. The gaseous emission from manure was reduced by 40%, 58% and 66% for chestnut tannin and spruce bark extract, larch bark extract and the tannin polymer, and oak tannin, respectively. For long-term nitrogen loss mitigation, 20% more nitrogen was preserved when spruce or larch bark extract or oak tannin was added to the manure compared to the reference measurements. A combination of the pH lowering effect of tannins and covalently bonding ammonia to flavonoid hydroxy groups provides a viable method for reduction of nitrogen loss in cattle manure.

Structure-Dependent Eco-Toxicity of Vegetable Tannin

Vegetable tannin is widely applied in various industries, in agriculture, and in water treatment as a natural polyphenolic compound; however, little data has been collected concerning the relationship between structure and eco-toxicity. Here, the toxicity of six commercial tannin and three model chemicals was assessed using Photobacterium phosphoreum. Two kinds of hydrolyzed tannin displayed higher bioluminescence inhibition than four kinds of condensed tannin, and the model chemical of hydrolyzed tannin also showed greater toxicity than those of condensed tannin, indicating the structure dependent eco-toxicity of vegetable tannin. The reactive toxicity mechanism was proposed, which was illustrated by molecular simulations based on the model chemicals and luciferase.

Tannin as a modulator of rumen microbial profile, apparent digestibility and ingestive behavior of lactating goats: A preliminary metagenomic view of goats adaptability to tannin

The aim with this study was to use interdisciplinary techniques and visions in order to identify the modulating effect of tannins on adaptive factors in lactating goats with different genetic patterns, through the assessment of digestibility and nutrient intake, ingestive behavior and rumen metagenome. We used in this study 8 of the Repartida ecotype and 6 of the Canindé breed goats, on average five years old, distributed in a completely randomized design, in a 2 × 2 factorial design, with two genetic groups and two diets. The applied diets were: basal diet and inclusion of 5% commercial tannin extract in basal diet. Intake and apparent digestibility of nutrients were evaluated, based on the quantification of the offered feed and refusals, and bromatological evaluation of samples of the offered feed, refusals and feces. Behavioral data were collected in 24-h continuous visual observations. The ruminal fluid was collected and DNA extraction, sequencing, and evaluation of relative abundance of the rumen microbiome were performed. The data obtained were analyzed statistically, through analysis of variance with 5% significance and, when necessary, a comparison of means test was applied. In this preliminary findings was observed that the genetic group factor caused changes in the number of chews and the relative abundance of microorganisms (P = 0.0290 and P = 0.0051). The diet factor influenced digestibility, which better values were observed for the tannin diet (P = 0.0049), in addition, it promoted changes in the rumen microbiota, with a beneficial modulatory characteristic. The inclusion of 5% tannin extract from Acacia mearnsii modulates the rumen microbiome, improving the apparent digestibility of nutrients without affecting the feed intake of goats from the Repartida and Canindé genetic groups.

Bio-Based Polyurethane Resins Derived from Tannin: Source, Synthesis, Characterisation, and Application

Tannins are soluble, astringent secondary phenolic metabolites generally obtained from renewable natural resources, and can be found in many plant parts, such as fruits, stems, leaves, seeds, roots, buds, and tree barks, where they have a protective function against bacterial, fungal, and insect attacks. In general, tannins can be extracted using hot water or organic solvents from the bark, leaves, and stems of plants. Industrially, tannins are applied to produce adhesives, wood coatings, and other applications in the wood and polymer industries. In addition, tannins can also be used as a renewable and environmentally friendly material to manufacture bio-based polyurethanes (bio-PUs) to reduce or eliminate the toxicity of isocyanates used in their manufacture. Tannin-based bio-PUs can improve the mechanical and thermal properties of polymers used in the automotive, wood, and construction industries. The various uses of tannins need to be put into perspective with regards to possible further advances and future potential for value-added applications. Tannins are employed in a wide range of industrial applications, including the production of leather and wood adhesives, accounting for almost 90% of the global commercial tannin output. The shortage of natural resources, as well as the growing environmental concerns related to the reduction of harmful emissions of formaldehyde or isocyanates used in the production of polyurethanes, have driven the industrial and academic interest towards the development of tannin-based bio-PUs as sustainable alternative materials with satisfactory characteristics. The aim of the present review is to comprehensively summarize the current state of research in the field of development, characterization, and application of tannin-derived, bio-based polyurethane resins. The successful synthesis process of the tannin-based bio-PUs was characterized by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), MALDI-TOF mass spectrometry, and gel permeation chromatography (GPC) analyses.

CONDENSED TANNINS OF THE SPECIES PINUS TAEDA: EXTRACTION, CHARACTERIZATION AND POTENTIAL FORMULATION OF WOOD BIOADHESIVE

The species Pinus taeda was evaluated as a source of condensed tannins for the potential formulation of phenolic adhesives from the extraction of the wood cortex. Extraction yield, percentage of tannins and non-tannins, and reactivity to the formaldehyde by the Stiasny number were analyzed in the responses of the extraction processes with extractive agents sodium sulfite (Na2SO3), sodium hydroxide (NaOH), and urea [(NH2)2CO] in the percentages of 2, 4, 6, 8, and 10 in relation to the weight of the bark of this species. The extracts were analyzed using the techniques of IR - Infrared Spectroscopy, SEM - Scanning Electron Microscopy, DRX- X-ray Diffractometry, and EDS - Energy-Dispersive X-ray Spectrometry. In another step, the formation time of the commercial tannin gel and of the P. taeda were compared in relation to formaldehyde. The results show that the specie have condensed tannins, and sustain that they are catechins. These catechins form polymers identified by SEM in less time in relation to the formaldehyde in the formation of the gel, suggesting that the tannins can be extracted from the species as a potentially new commercial source that lumber companies can use to manufacture phenolic resins.

COMPLEMENTARY ANALYTICAL TECHNIQUES PAPER, THIN-LAYER, HIDE-POWER, AND COMBINED METHODS FOR CHARACTERIZATIONOF TANNIN IN PLANTS

The polyphenolic compoundsextract rich in gallo-catechol tannins submitted to complementary analytical techniqueswas evaluated. The whole plantspecies screened were of the condensed type except Acacia seyal var. fistuala, Acaciaseyal var. seyal, Casuarina equistifolia, and Pithecellobium dulcewere of mixedhydrolysable-condensed(gallo-catechol) type. The quantitative data indicated that 5 parts (bark) out of 12 species, when extracted, contained more than 10% tannins (oven-dry basis), the level of commercial interest. The catechin numbers indicated that all the studied species contained condensed tannin in varying amounts (0.6-45.7), while the presence of both gallic acid and catechin means that the tannin is of mixed type. Thin-layer and paper chromatography with different solvent systems confirmed the presence of catechin and gallic acid, and showed that tannic acid, fisetin, epicatechin and some unidentified phenolics were present. However, dihydrofisetin and robinetin, which were used as standards, were not detected. Astringency values shows that the Acacia mellifera(0.18), Acacia seyalvar.fistuala(0.18), Pithecellobium dulce (0.15), Acacia senegal (0.14), Acacia farnesiana (0.13), Calotropis procera (0.13)barks could be used in place of A. mearnsii(international commercial tannin materials) (0.16) because the degree of relative astringency or the ability of their tannin to combine with protein is close to that of A. mearnsii in other words these six species can give leather with characteristics comparable with that of A. mearnsii.

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.

Chemical Derivatization of Commercially Available Condensed and Hydrolyzable Tannins.

Novel valorization routes for tannins were opened by the development of a simple, straightforward, robust, and flexible approach to the selective functionalization of condensed and hydrolyzable tannins. Irrespective of the different degrees of polymerization, different commercial tannins were efficiently functionalized by the generation of an ether linkage bound to a short linker carrying the desired functional group. Functionalizations could be realized at varying degrees of technical loadings, i.e., amounts of introduced tannin-alien functionalities per number of phenolic hydroxyl groups. The same strategy was found suitable for the synthesis of polyethylene glycol-functionalized tannin copolymers. Condensed tannins functionalized with carboxylic acid moieties could be converted into a tannin–oligopeptide hybrid.