Tannins sources

The condensed tannins are polyphenolic with a pK of -8.6, so that a 10% w/v solution in water would be expected to have a pH — 4.5. Proanthocyanidins may be solubilized by the addition of base through formation of phenoxide ions. Extraction of tannin sources with either sodium carbonate or sodium hydroxide... 

Fig. 1. An amplified outline scheme of the making of various wiaes, alternative products, by-products, and associated wastes (23). Ovals = raw materials, sources rectangles = wines hexagon = alternative products (decreasing wine yield) diamond = wastes. To avoid some complexities, eg, all the wine vinegar and all carbonic maceration are indicated as red. This is usual, but not necessarily tme. Similarly, malolactic fermentation is desired in some white wines. FW = finished wine and always involves clarification and stabilization, as in 8, 11, 12, 13, 14, 15, 33, 34, followed by 39, 41, 42. It may or may not include maturation (38) or botde age (40), as indicated for usual styles. Stillage and lees may be treated to recover potassium bitartrate as a by-product. Pomace may also yield red pigment, seed oil, seed tannin, and wine spidts as by-products. Sweet wines are the result of either arresting fermentation at an incomplete stage (by fortification, refrigeration, or other means of yeast inactivation) or addition of juice or concentrate.

A considerable quantity of oil can be extracted from waste material from shelling and processing plants, eg, the inedible kernels rejected during shelling and fragments of kernels recovered from shells. About 300 t of pecan oil and 300—600 t of English walnut oil are produced aimuaHy from such sources. The oil is refined and used for edible purposes or for the production of soap the cake is used in animal feeds (see Feeds and feed additives). Fmit-pit oils, which closely resemble and are often substituted for almond oil, are produced on a large scale for cosmetic and pharmaceutical purposes (143). For instance, leaves, bark, and pericarp of walnut may be used to manufacture vitamin C, medicines, dyes and tannin materials (144). 

Tannin-containing woods can also suffer from dark-brown stains produced by alkali, usually from a concrete or a detergent source. Conversely, fair-faced concrete can be similarly stained by the run-off water from unprotected hardwood surfaces. Some woods, e.g. afzelia, ayan and idigbo, give yellow contaminating dyes with alkaline detergents and should not be used in washrooms and kitchens. 

Tannin-containing woods also darken with ammonia, a process which is usefully employed in darkening oak furniture by fuming . Ammonia stains can originate from animal glue, amino-type adhesives and concrete additive sources, particularly where damp conditions exist. 

The tannins are synthesized by plants and are abundantly distributed in many different forms of plant life. Common sources of tannins include for example, the bark, leaves, fruit and roots of many plants most tannins, however, have been and are still derived from the bark of a few trees and shrubs, such as oak, chestnut, hemlock, mangrove, quebracho, and wattle, from which they are generally extracted with water. 

All the tannins readily react with proteins, forming insoluble, stable compounds when they react with collagen, the main constituent of animal skin, they form leather, a material that is resistant to hydrolysis, oxidation, and biological attack and therefore stable to weathering and resistant to decomposition. Since tannins from different plant sources have different chemical compositions, each tannin used for tanning skin produces a leather having slightly different properties and color. Tannins that have... 

Proanthocyanidins (PAs), also known as condensed tannins, are oligomeric and polymeric flavan-3-ols. Procyanidins are the main PAs in foods however, prodelphinidins and propelargonidins have also been identified (Gu and others 2004). The main food sources of total PAs are cinnamon, 8084 mg/100 g FW, and sorghum, 3937 mg/100 g FW. Other important sources of PAs are beans, red wine, nuts, and chocolate, their content ranging between 180 and 300 mg/100 g FW. In fruits, berries and plums are the major sources, with 213.6 and 199.9 mg/100 g FW, respectively. Apples and grapes are intermediate sources of PAs (60 to 90 mg/100 g FW), and the content of PAs in other fruits is less than 40 mg/100 g FW. In the majority of vegetables PAs are not detected, but they can be found in small concentrations in Indian squash (14.8 mg/ 100 g FW) (Gu and others, 2004 US Department of Agriculture, 2004). 

The cacao plant, Theobroma cacao, is the source of chocolate which is well known and highly prized in international commerce. The cacao pods contain beans which are fermented and pressed to provide a brown liquid which is the raw material for chocolate. The press cake is ground and sold as cocoa and it also provides a brown colorant. The pods, beans, shells, husks and stems have also been suggested as colorants. They contain a very complex mixture of acyl acids, leucoanthocyanins, flavonoid polymers, tannins, and catechin-type polymers.33... 

The plant Stevia rebaudiana bertoni has been studied in depth because it was discovered that this plant is the source of six sweet-tasting diterpene glycosides. They are stevioside, rebaudiosides A, C, D, E and dulcoside A. (Table 1). These sweet diterpene glycosides, as well as a complex mixture of organic compounds of which more than a hundred compounds have been identified, are found mainly in the leaves of the plant. The leaves contain a complex mixture of labdane diterpenes, triterpenes, stigmasterol, tannins and volatile oils. There is an abundance of reviews and patents relating to these sweet diterpene glycosides. 

Key headings indicate the herbivore(s) and source(s) of tannin in the diet (which is either artificial [AD] or vdiole-plant [P]). The findings of each study are then listed in categories A-E as described in the main text. Abbreviations used below are explained in Table II. 

A Tannins and oils in sane grasses may reduce CR but only when the animal is restricted in alternative food sources. 

Condensed tannins were considered to be highly recalcitrant to biodegradation until Basaraba (3) reported that some bacterial isolates could utilize wattle tannin as both a carbon and energy source. Later, Lewis and Starkey... 

Yeasts. An interesting paper published in 1984 (59) claimed that rat-caecal microflora degraded catechin. To our knowledge no paper has dealt with yeasts, other than that some yeasts degrading wattle of quebracho tannins were able to grow weakly with catechin as a sole carbon source (32). 

The APCI source (Table 2.8) has been used for the analysis of various flavonoids, especially flavonols, flavones, flavanones, and chalcones (Table 2.11). APCI is based on gaseous-phase ionization, and is most suitable for compounds that are partially volatile and have a medium polarity. Thus, the application of APCI with respect to analysis of condensed tannins and anthocyanins is more limited. Compared with ESI, APCI produces more fragment ions in the spectrum due to the harsher vaporization and ionization processes. More information about ESI and APCI can be found in Section 1.4.5. 

These herbs contain high ieveis of tannins (piant products that have an astringent taste). Source Yaie New Haven Heaith. Avaiiabie oniine. URL http //yaienewhavenheaith.org/iibrary/heaithguide/en-us/Cam/topic.asp hwid=hn-l 197005. Accessed May 20, 2006. 

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