Technological Application of Tannin-Based Extracts (original) (raw)
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Tannins as a sustainable raw material for green chemistry: A review
Industrial Crops and Products, 2018
Tannins as herbal extracts are a good alternative for green chemistry. They are found aplenty in some plant species and can be extracted by simple methods. The tannins main feature and advantage is their phenolic structure which is very similar to synthetic phenols. Another key feature of tannins is their actions as antioxidants. The use of tannins is often connected to one of these features. They are now actively used in leather tanning, adhesive making (especially wood adhesives), fisheries, beverages manufacturing, animal feed and many others. Considerable amounts of research has also been recently conducted on the possibility of using tannins in the manufacture of biosourced foams, wood preservatives, corrosion inhibitors, polyurethane surface coatings, epoxy adhesives, binders for Teflon coatings and etc. This paper deals with different uses of tannins and with the latest research which has been done on this subject.
Foods, 2021
During recent decades, consumers have been continuously moving towards the substitution of synthetic ingredients of the food industry by natural products, obtained from vegetal, animal or microbial sources. Additionally, a circular economy has been proposed as the most efficient production system since it allows for reducing and reutilizing different wastes. Current agriculture is responsible for producing high quantities of organic agricultural waste (e.g., discarded fruits and vegetables, peels, leaves, seeds or forestall residues), that usually ends up underutilized and accumulated, causing environmental problems. Interestingly, these agri-food by-products are potential sources of valuable bioactive molecules such as tannins. Tannins are phenolic compounds, secondary metabolites of plants widespread in terrestrial and aquatic natural environments. As they can be found in plenty of plants and herbs, they have been traditionally used for medicinal and other purposes, such as the le...
Applications of Tannins in Industry
Tannins - Structural Properties, Biological Properties and Current Knowledge [Working Title]
Tannins are water-soluble natural polyphenols mainly present in plant-based materials, including food. Tannins play a very significant role as a raw material for sustainable green industries. Therefore, they are mainly used in diverse types of industries such as leather, feed, fisheries, beverages, etc. They also find application as potential medicinal agents, antioxidants, metal chelators; and cater as inhibitors of harmful pro-oxidative enzymes and of lipid peroxidation process. Recently, several important properties like antiseptics, anticarcinogenic, and anti-inflammatory of tannins have been documented in the human that make them suitable candidates for pharmaceuticals and nutraceutical industries. Because of current concerns related to synthetic compounds used in the human health and food industries, which leave highly adverse effects on the human body and environment, tannins can offer an alternative to these harmful chemicals in recently emerging industries.
Tannins: Current knowledge of food sources, intake, bioavailability and biological effects
Molecular Nutrition & Food Research, 2009
Tannins are a unique group of phenolic metabolites with molecular weights between 500 and 30 000 Da, which are widely distributed in almost all plant foods and beverages. Proanthocyanidins and hydrolysable tannins are the two major groups of these bioactive compounds, but complex tannins containing structural elements of both groups and specific tannins in marine brown algae have also been described. Most literature data on food tannins refer only to oligomeric compounds that are extracted with aqueous-organic solvents, but a significant number of non-extractable tannins are usually not mentioned in the literature. The biological effects of tannins usually depend on their grade of polymerisation and solubility. Highly polymerised tannins exhibit low bioaccessibility in the small intestine and low fermentability by colonic microflora. This review summarises a new approach to analysis of extractable and non-extractable tannins, major food sources, and effects of storage and processing on tannin content and bioavailability. Biological properties such as antioxidant, antimicrobial and antiviral effects are also described. In addition, the role of tannins in diabetes mellitus has been discussed.
Purification of industrial tannin extract through simple solid-liquid extractions
Industrial Crops and Products, 2019
Acacia Mimosa or black wattle (Acacia Mearnsii) industrial tannin extracts are used as such for leather tanning, water flocculants, adhesives and many other applications. However, when higher purity of the polyphenols is requested, these extracts are not suitable anymore. Therefore, feasible strategies have to be developed in order to improve the purity of the extract. Solid-liquid extractions with common solvents were performed and the soluble and insoluble fractions of the tannin extracts in methanol and acetone were quantified and characterized through chemical analysis of phenolics, FT-IR, Py-GC/MS, LC-UV/ESI-MC and GPC. It was observed that the solvent soluble fractions were enriched of polyphenols, the insoluble residue after methanol extraction was the one presenting higher amount of hydrophobic compounds and the fraction soluble in acetone resulted purified of proteins. However, these encouraging findings suggest that this strategy does not allow to separate the phenolics from the saccharidic components which appear to be intimately interconnected.
Insight into the characterization of commercial oenological tannins
Food chemistry advances, 2023
The characterization in terms of phenolics, antioxidant capacity and oxygen consumption rate (OCR) was carried out for 15 commercial oenological tannins of different origin. A NMR approach was used to evaluate their average molecular weight, and their glycosidic and aromatic moieties. The investigated oenological tannins showed wide differences in their chemical properties. Total phenol index (TPI) ranged from 461 ± 28 and 1018 ± 57 mg gallic acid/g for cherry tannin and nut gall tannin, respectively. The antioxidant capacity, positively correlated with TPI, was higher for hydrolysable tannins ranging 3.05 ± 0.06 and 12.06 ± 0.71 mM Trolox/g for ABTS assay, and from 3.70 ± 0.23 and 10.94 ± 1.28 mM Trolox/g for DPPH assay. Relevant differences in OCRs were found and chestnut tannin showed the highest OCR. Wide range of molecular weights were found with nut gall 1 tannin showing the highest one, ranging from 790 to 1900 Da. This study improves and expands the actual knowledge of tannins supporting the suitability of NMR for the characterization of oenological tannins.
Extraction of Condensed Tannins from Mexican Plant Sources
Zeitschrift für Naturforschung C, 2008
Contents of total polyphenols, condensed tannins and proanthocyanidins, and their stability to various pH values and temperatures were studied in Mexican blueberry, cuautecomate fruit, garambullo fruit, aubergine, coffee pulp and residues of black grapes. Several aqueous extracts, obtained through a one-pass-extraction process, were analyzed using liquid chromatography in order to quantify the condensed tannin (proanthocyanidin) content responsible for their antioxidant activity and colour. All tested samples included high proanthocyanidin contents demonstrating that these Mexican fruits and vegetables are good sources of natural antioxidants, and they all could be considered as excellent functional foods due to their bioactivity measured as the condensed tannin level.
Analysis of hydrolysable tannins
Animal Feed Science and Technology, 2001
This review deals with the main issues relating to the analysis of hydrolysable tannins (HTs). It covers brie¯y their distribution in the plant kingdom and describes their main structural features. HTs have often been ignored because they are apparently more dif®cult to analyse than condensed tannins. Meaningful analytical data are critically dependent on appropriate sample preparation, storage and extraction techniques. This requires some understanding of the reactivities of hydrolysable tannins. Mixtures of HTs have been measured by general tannin assays, such as precipitation with metals or proteins, and by colorimetric assays for total phenols. Some HTs can also be measured by more speci®c colorimetric tests. Although colorimetric assays are widely used for tannin analyses, they generally do not provide accurate quantitative data. At best, they provide data for comparative purposes. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) are useful tools to screen samples for the different types of tannins, hydrolysable or condensed tannins. In addition, there are physicochemical techniques, such as nuclear magnetic resonance (NMR) and mass spectrometry (MS), which are used to identify pure tannin compounds. More recently, other MS techniques have been developed that are capable of yielding molecular weights of crude tannin mixtures.
International Journal of Pharmaceutical and Biological Science Archive, 2015
This review was investigated and identification structure, role of the tannins in plants structure. Tannins are a complex group of polyphenolic compounds found in a wide range of plant species commonly consumed by ruminants. They are conventionally classified into two major groups:-the hydrolysable and the condensed tannins. During growth and maturation period in plants some substances can be found in structure of them which they have essential role in plant fortune. These substances are called plants secondary metabolites. One of the most important of secondary metabolites is Tannins. A great deal of research with tannins has followed an approach that looks at biological relationships: taxonomy, phylogeny, biosynthesis, nutritional and physiological effects on herbivorous animals e.g. ruminants. Their antimicrobial properties seemed to be associated with the hydrolysis of ester linkage between gallic acid and polyols hydrolyzed after ripening of many edible fruits. Tannins in these fruits serve as a natural defense mechanism against microbial infections. The antimicrobial property of tannic acid can also be used in food processing to increase the shelflife of certain foods, such as catfish fillets. Tannins have also been reported to exert other physiological effects, such as to accelerate blood clotting, reduce blood pressure, decrease the serum lipid level, produce liver necrosis, and modulate immunoresponses. The dosage and kind of tannins are critical to these effects. The aim of this review is to summarize and analyze the vast and sometimes conflicting literature on tannins and to provide as accurately as possible the needed information for assessment of the overall effects of tannins.