Tannins continued

The classic seed burial studies of W. J. Beal and his successors have shown seeds of at least one weed species, Moth Mullein (Verbascum blattaria L.) can remain viable in soil for a peiod of 100 years, whereas three species continued to germinate after 80 years of burial (30). Weed seeds not only resist decay by soil microbes, but they vary in dormancy characteristics. There is considerable evidence that chemical inhibitors are responsible for both phenomena. Unsaturated lactones and phenolic compounds in particular, are potent antimicrobial compounds present in many seeds (4J. Fruits and seeds are also known to contain diverse germination inhibitors including phenolic compounds, flavonoids and/or their glycosides and tannins. Unique methods to destroy inhibitors could provide an excellent weed management strategy. 

Laouenan, P. et al., NMR structural investigations and conformational analysis of condensed tannins. A continuing challenge due to restricted rotation about the interflavanyl linkage, Analusis, 25, M29, 1997. 

Some of the early descriptions of the effect of MOX on red wine included an interesting cycling effect where certain organoleptic aspects of wine quality appear to get worse before the continued application of MOX leads to the desired improvements (Dykes and Kilmartin, 2007 Parish et al., 2000 Vinovation, 2009). In the first "structuring" phase (for several days to weeks), the wine tannins are said to become more aggressive and the varietal aromas decrease, after which the tannins soften and... 

On, ok Chamois Leather—TIiIb article, takes its name from the skins of the chamois but, although the term is still retained, those of sheep, deer, lambs, and the tliin portion of split hides and skins, are now converted into it. It is different from any of the varieties hitherto described, bcoause neither tannin nor mineral matters enter Into its formation the conservation being entirely effected by means of oils and fats. Further, the finest, aB well as tire coarsest quality known as wash-leather, receive precisely the same treatment, and consequently the difference they present is owing to the circumstance, that the finest skins are chosen for tho former, whilst the inferior ones are mado into the latter. In the last, sixteenth, and earlier centuries, the trade in chamois leather was much more considerable than at prosent because, in those periods, it was extensively used for clothing, particularly in the armies. It is now, however, abandoned for this purpose, in consequence of its permeability, owing to which it readily absorbed moisture, and parted with it bnt slowly qualities which kept the wearer in continual. danger of cold and rheumatic complaints. 

The complete results are in Table XIV which shows the development of phenolic compound content during maceration. The anthocyanins increase until about the sixth day and then decrease. The tannins, on the other hand, increase continually, probably because they are more abundant, especially after the seeds are added. However, in some cases peculiar to vintages low in tannins, the production of these compounds is the same as that of anthocyanin. 

During aging the anthocyanins continue to disappear by condensing with tannins which themselves undergo an oxidative condensation resulting in a color shift from yellow to orange-brown. Finally it is these tannins which play the most important role in the characteristic color of old wines. 

Phenolic compounds and flavonoids are a unique category of plant phytochemicals especially in terms of their vast po ential health-benefiting properties. They represent the most abundant and the most widely represented class of plant natural products. A substantial amount of research has been carried out over the past two decades yet large information gaps still exist. For example, the inventory of these compounds is still incomplete, although there is continuous effort to provide new structures. In addition the dissection of the metabolic pathways for certain phenolic compounds remains to be resolved. Recent reports underline that important questions that still need to be answered in the field of proanthocyanidin and tannin biosynthesis [Xie and Dixon, 2005], and even the exact nature of the biosynthetic pathway(s) leading to lignin monomers is not fully elucidated. 

Basic dyes of the azo class were among the earliest known synthetic dyes. They were used originally for dyeing cotton mordanted with tannin and potassium antimonyl tartrate and wool from neutral solution. They continue to have minor importance for dyeing leather, paper, plastics, and waxes, and as constituents of graphic arts colors. 

European special-purpose rotating tanks have been used successfully by at least one North Coast winery, but the cost of the equipment and space required has discouraged expansion of this facility. Continuous fermentation systems have been introduced in foreign countries but are only in very limited use in northern California. Dangers of contamination, cooling difficulties, and the need for a continuous flow of must make them unsuited for premium wine production. Heating is another way to liberate color and tannins from the skins but until recently all experiments have produced wines of inferior quality and, therefore, have not been used in the coastal counties of California. 

Fig. 1-2. Transverse section of xylem and phloem of red spruce (P/cea rubens). CZ, cambial zone DP, differentiating phloem MP, mature phloem with sieve cells (sc) and tannin cells (tc) DX, differentiating xylem with ray cells and tracheids (tr) MX, mature xylem, earlywood (EW) with resin canals (rc), lined with epithelial cells (ec) LW, latewood. Note that each ray continuous from the xylem, through the cambial zone, and into the phloem. Light micrograph by L. W. Rees. Courtesy of Dr. T. E. Timell.

The rapid growth of the pulp and paper industry following World War II coupled with a renewed scientific interest in utilization of bark and wood residues led to investigative programs on bark and wood tannins. The leather industry was continuing to decline in importance, so other alternatives were needed. One of these was replacement of phenol in whole or in part in phenol-formaldehyde adhesive formulations. This work progressed to the point where commercial quantities of polyphenolic extractives were made and sold for adhesive application. Excessive capacity and low petrochemically derived phenol prices in the 1960 s led to the demise of this effort in the United States (2,5). 

Progress in the use of condensed tannins in adhesive formulations might be expected to be more rapid than is the case for lignins because of the impetus provided by the commercialization of wattle tannin-based adhesives and because of the extraordinarily high reactivity of tannins in reactions with formaldehyde. This reactivity offers an opportunity to substitute tannin for resorcinol (currently priced at about 1.80/lb) instead of phenol (about 0.40/lb). Now that wattle tannins have been successfully introduced, their application can be expected to continue to expand. The situation remains difficult, on the other hand, for use of conifer bark tannins in adhesives. Herb Hergert is certainly... 

Anthocyanin content reaches a maximum early in fermentation (Nagel and Wulf 1979) whereas tannin extraction continues throughout pomace contact (Singleton and Draper 1964). Monitoring of red must flavonoid composition during maceration showed that the extraction of flavonols and of proanthocyanidins from skins roughly parallels that of anthocyanins while that of seed flavanols is slower (Cheynier et al. 1997b Morel-Salmi et al. 2006). The initial rate of flavonoid... 

Continuous operation possible high output few breakdowns high tannin and suspended solids content severe oxidation... 

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