Vanillin procedure

The vanillin procedure involves reaction of an aromatic aldehyde, vanillin, with the meta-substituted ring of flavonols to yield a red adduct. Although the vanillin assay is used for the estimation of condensed tannins (proanthocyanidins), the... 

A large number of patents describe various procedures for the mainly continuous hydrolysis and oxidation processes, as weU as for the purification steps requited to obtain high grade vanillin. Lignin is degraded either with sodium hydroxide or with calcium hydroxide solution and simultaneously... 

Pyrogallol monomethyl ether has been prepared by the methylation of pyrogallol with dimethyl sulfate or methyl iodide by the decarboxylation of 2,3-dihj droxy-4-methoxy-benzoic acid and by the methylation of pyrogallol carbonate with diazomethane and subsequent hydrolysis. The method described is taken from the improved procedure of Baker and Savage for the preparation of pyrogallol monomethyl ether from o-vanillin by oxidation with hydrogen peroxide. 

Aroma chemicals which are found in natural sources or food preparations but are synthesised by normal chemical procedures are defined by the status nature-identical . Most of them were discovered and developed during the nineteenth and twentieth centuries. The most important single aroma chemicals produced in very large amounts are vanillin, menthol, citral and anethol. They are used not only by flavour producers but also in large amounts in fragrance... 

Another product that is produced commercially from the alkaline hydrolysis of lignin is vanillin. It was found that the yield could be improved by the presence of oxygen during the alkaline hydrolysis reaction. A number of commercial ventures have been based on this procedure (8,9). 

Methods of analysis are needed to determine total phenolic content and the relative content of phenolic fractions by means of their different characteristics. Many analytical methods used for phenols have been empirical and not easily reproduced or rationalized (I). Procedures that are based on sound chemical principles and that are sufficiently verified deserve wider application. We are concerned here with recent work on such analyses for phenols in wines. Application cf these results may help solve a major problem in phenol research—the many different, too empirical, unrelatable values (ml KMn04, vanillin-to-leucoantho-cyanin ratio, etc.) obtained in different ways by different researchers. Uniform use of verified methods and uniform standards and methods of expressing results will aid in developing an understanding in this field. 

There are a large number of other published procedures for the separation of a number of sweeteners and preservatives at one time these are all based on reverse-phase HPLC. Perhaps one of the most startling is the method published by Williams (1986). This uses a small particle size (3 xm) C8 column and allows the separation of a range of colours, sweeteners and preservatives in less than 5 min. The materials separated were amaranth, quinoline yellow, quinine sulphate, sunset yellow, caffeine, aspartame, saccharin, vanillin, sorbic acid, benzoic acid and green S. 

Affinity of MIP towards the target analyte should be examined prior to fabrication of the chemosensor. Batch binding assays are used to test selectivity of suitable MIPs. Especially, affinity of MIP to compounds, which are structurally related to the target analyte, should be tested. If MIP binds similarly with these compounds as the template, then cross-reactivity is manifested [156], This effect was exploited for determination of adenine and its derivatives with the use of MIP templated with 9-ethyladenine. Nevertheless, the cross-reactivity, if undesired, can be avoided by suitable sample pretreatment, e.g. by interferant extraction with a supported liquid membrane (SLM) coupled to the MIP-PZ chemosensor. The Fluoropore membrane filter of submicrometre porosity can serve that purpose. That way, this membrane holds interferants, thus eliminating the matrix effect. The SLM-involving determination procedure is cheaper than traditional laborious sample pretreatment used to remove the interfering substances. For instance, caffeine [143] and vanillin [157] in food samples have been determined using this procedure. 

Methyl 4-0-(4-methoxybenzyl)2,3-di-0-methyl-oc-D-glucopyranoside has been prepared [371] by Liptak s procedure (see Sect. 2.6). This lithium aluminium hydride — aluminium trichloride method was also used in the synthesis of 4-hydroxy-3-methoxy-benzyl [372], 4-hydroxy-3,5-dimethoxybenzyl [372], and 1-phenylethyl [373] ethers from the 4,6-acetals derived from vanillin, syringealdehyde, and acetophenone. Various vinylbenzyl ethers were prepared by the reaction of carbohydrates with vinylbenzyl chloride, and copolymerized with styrene [374]. 

A laboratory synthesis for vanillin is based on this procedure. 2-Hydroxytetrahydro-furan, an intermediate for cytostatics, was produced from the corresponding carboxylic acid by electrochemical oxidation 253 ... 

A very different source, vanillin, has also given accurate results. A saturated solution of vanillin is prepared by dissolving vanillin in ethanol and by adding a small portion of this solution to the basic analyte solution, NaOH. This type of olfactory titration is more appealing to students due to the pleasant aroma of the vanillin. Instructors might find this titration more attractive as well since the concentration of the NaOH is only 1M versus the 2 M required to quench the aromas of onions and garlic. A detailed account of the chemistry involved, procedures, and student handouts is available (Neppel et al. 2005). 

Bettazzi et al. (2006) developed a disposable electrochemical sensor for the detection of vanillin in vanilla extracts and in commercial products. An analytical procedure based on square-wave voltammetry (SWV) was optimized and a detection limit of 0.4 pM for vanillin was found. The method was applied to the determination of vanillin in natural concentrated vanilla extracts and in final products such as yoghurt and compote. The results obtained with electrochemical quantification of vanillin in the extract samples correlated well with the HPLC results. 

Kahane et al. [169] first oxidized vanillylmandelic acid, after its extraction from urine by the action of sodium periodate, to vanillin. The vanillin was then converted into the methyloxime by reaction with methoxylammonium chloride and finally silylated. The recovery of the total procedure, including extraction from urine, is said to be minimally 95%, with the resulting derivative being highly specific for the compound under analysis. The GC analysis was performed on QF-1 as stationary phase. 

Secondary metabolites produced by plant cell culture are commonly accumulated in the cells. With few exceptions such as Capsicum frutescens, Thalictrum minus (9) and Vanilla planifolia (Knorr, D. and Romagnoli, L., Univ. of Delaware, unpublished data) cultures, which release valuable compounds such as capsaicin, berberine and vanillin, respectively, into the medium, procedures to induce product release are required to develop continuous production processes. Reported permeabilization methods include treatment with dimethylsulfoxide (DMSO), isopropanol, toluene, phenethyl alcohol or chloroform (9, 28). But as Fontanel and Tabata (9) pointed out, such treatments with organic solvents are severe and other methods of permeabilization need to be developed. 

Alkaline oxidation of lignin is the commercial source of vanillin. This procedure converts a significant portion of the lignin to aromatic fragments that are, for the most part, aromatic aldehydes. The mechanism probably involves two steps, hydrolysis of the aryl ether linkages followed by side chain oxidation. 

Alkylation of the hydroxy aromatic compound to the corresponding alkoxy aromatic compound may be performed in accordance with known alkylation procedures in which the hydroxy aromatic compound is reacted with an alkyl sulfate, alkyl halide or alkyl sulfonate in a suitable solvent, usually water, containing a base such as sodium hydroxide. Such reactions are shown at various places in the literature, as for ex. in Organic Synthesis, Col. Vol. II, page 619, 1943, in which veratraldehyde is prepared from vanillin. The iodide salt may, if desired, be recaptured subsequent to the alkylation reaction. 

A solution of 1 mole of salicylaldehyde in 1 1. of 1 iV sodium hydroxide is treated at room temperature with 1.2 moles of 3% hydrogen peroxide. The solution darkens and the temperature rises to 45-50°. After 15-20 hrs. the mixture is neutralized with acetic acid and evaporated to dryness at room temperature, and the residue is extracted with toluene. A procedure later applied to o-vanillin specifies that the reaction be run in a stream of nitrogen. ... 

For oxidation of vanillin to vanillic acid, PearF used an economical procedure which is unique to p-hydroxybenzaldehydes. Whereas aldehydes of other types, like 3-thenaldehyde, require two moles of silver nitrate for alkaline oxidation, a p-hydroxyaldehyde requires only one mole of reagent. Pearl mixed aqueous CHO CO2H... 

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)... 

When the whole set of vanillin samples from different origins is considered, we are faced with the necessity of choosing a classification procedure and defining belonging rules. 

It is obvious that the same limits as those described for the classification step apply to this procedure and a Monte-Carlo simulation should refine the determination of the mixture composition. The only drawback of the Monte-Carlo approach is the computation time since in the case of four isotope ratios measured for three groups of vanillins, a 1 % precision requires 10E11 tests, i.e. one week of computation for a 60 MHz-Pentium based micro-computer (ref. 5) ... 

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