Vanillin from wood

In such cases, determination of the ratio between the stable isotopes carbon-12 and carbon-13 may be a way to differentiate between different sources of botanical origin, reflecting differences in the CO2 assimilation pathways. This procedure has only been used with some degree of accuracy in a limited number of cases such as the distinction between vanillin from vanilla beans and vanillin from wood lignin. (14)... 

The Norwegian company Borregaard makes vanillin by chemo-oxidation of cheap natural lignin. In view of the complexity of the lignin structure this is a remarkable achievement. This semi-synthetic vanillin is, however, not allowed to carry the qualification of natural . Borregaard is the only global producer of lignin-vanillin or wood-sourced vanillin , with a volume of about 2000 t a-1. They obtain 4 kg vanillin from one ton of wood. This vanillin is more expensive than synthetic vanillin, but the flavorist needs lower doses of the extra round flavor . 

Nowadays, synthetic vanUlm is obtained predominantly from petrochemical sources. For vanillin, the key compound is guaiacol (o-methoxyphenol). This is obtained initially from wood tar, coal tar, wood distillate or lignite distillate. Targeted syntheses start from benzene via dichlorobenzene, catechol may be obtained, which is further monomethylated. The second route begins with the oxidation of cumene (the so called Hock synthesis ) to give phenol, and continues with nitration, methylation, reduction, diazotisation and heating of the diazonium salt solution. [142]... 

CaH803. Fine white needles, m.p. 82°C, b.p. 285°C, strong vanilla odour, characteristic taste. It occurs extensively in nature, and is the odoriferous principle of the vanilla pod it can be obtained from the glucoside coniferin. Vanillin is made commercially from the ligno-sulphonic acid obtained as a by-product in the manufacture of wood pulp. It is one of the most important flavouring and perfuming... 

Vanilla flavoring in bakery goods, confectionery, and many fro2en desserts need not be natural vanilla. The artificial and synthetic vanilla flavors that are used include vanillin [121-33-5] from lignin (wood pulp), ethyl vanillin [121 -32-4] and vanitrope [94-86-0], the latter two are synthetics. Over 90% of the U.S. market for vanilla flavor contains vanillin. These synthetics continue to dominate the market because of availabiUty, quahty, and relatively low and stable prices. 

It has been shown that aromatic aldehydes including vanillin, syfingaldehyde, coniferaldehyde, siaapaldehyde, and ethyl lignin come from charred wood, the length of matufing directly affects the amount of aldehydes formed, the lower proof spirits have more aldehydes than higher proof spirits do, and the used and new uncharred barrels produce about one-third of the aromatic aldehydes found ia new charred barrels (Table 3) (8). 

Catechol is also obtained from coal coking and from certain wood residues. Vanillin (synthetic vanilla flavoring) is a catechol derivative. Resorcinol and hydroquinone are currently made by the same type of chemistry used... 

The use of the lignin fraction is much more cumbersome currently the best-known chemical of a real commercial importance is vanillin, which is obtained by oxidation of the black liquor. Another example is a product called spray-dried lignosulfonate (as sodium salt) obtained from the older, acidic sulfite pulping process. It is sold as a commercial product primarily as a concrete additive for enhanced strength. Since the cement industry is one of the big contributors of carbon dioxide emissions (due to the production of calcium oxide from calcium carbonate), the use of this renewable, wood-derived product not only is fossil-carbon neutral in itself but also reduces carbon dioxide emission due to the diminished need for cement in large infrastructures made of concrete. 

The second pathway using VAO reported by van den Heuvel et al. [83] is the VAO-catalysed oxidation of vanillyl alcohol to vanillin. Vanillyl alcohol is not very abundant in nature but can be generated by VAO-catalysed conversion of creosol (2-methoxy-p-cresol). As creosol can be found in creosote obtained from heating wood or coal tar, the feedstock for this pathway is very abundant. 

Many aldehydes are particularly fragrant. A number of flowers, for example, owe their pleasant odor to the presence of simple aldehydes. The smells of lemons, cinnamon, and almonds are due to the aldehydes citral, cinnamalde-hyde, and benzaldehyde, respectively. The structures of these three aldehydes are shown in Figure 12.21. The aldehyde vanillin, introduced at the beginning of this chapter, is the key flavoring molecule derived from the vanilla orchid. You may have noticed that vanilla seed pods and vanilla extract are fairly expensive. Imitation vanilla flavoring is less expensive because it is merely a solution of the compound vanillin, which is economically synthesized from the waste chemicals of the wood pulp industry. Imitation vanilla does not taste the same as natural vanilla extract, however, because in addition to vanillin many other flavorful molecules contribute to the complex taste of natural vanilla. Many books made in the days before acid-free paper smell of vanilla because of the vanillin formed and released as the paper ages, a process that is accelerated by the acids the paper contains. 

Vanillin, syringaldehyde, and related phenolic products derived from lignin appear to be important in the desirable odor contributed to beverages by oak barrels (25, 26, 27). These substances are present in the wood, but more appears in the beverage than simple extraction seems to allow. Also the odor of vanillin seems to increase with time and mellowing of the beverage compared with a fresh extract of new wood (25). 

Vanillin structures can be considered to be minor lignin end groups and compounds containing vanillin moieties were isolated from all wood and pulp samples. The yields were, however, much lower than those of either coniferyl alcohol... 

Vanillin is obtained from sulfite waste liquor by further alkaline hydrolysis of lignin. It is the same substance that can be obtained from vanilla bean extract and is the common flavoring in foods and drinks. Natural and synthetic vanillin can be distinguished from each other by a slight difference in the amount of 13C in their structure, since one is biosynthetic in the bean and the other is isolated from a second natural product, wood, by hydrolysis of the lignin. 

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