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Phenolic compounds heating

Preliminary indication of the presence of a phenol ester may be obtained by heating the compound with soda-lime esters of phenols and also aromatic hydroxy-acids usually give the phenol. (Likewise amides, Imides, nitriles, substituted hydrazines, uretheines, etc. eifiord ammonia.)... [Pg.1064]

Various extraction methods for phenolic compounds in plant material have been published (Ayres and Loike, 1990 Arts and Hollman, 1998 Andreasen et ah, 2000 Fernandez et al., 2000). In this case phenolic compounds were an important part of the plant material and all the published methods were optimised to remove those analytes from the matrix. Our interest was to find the solvents to modily the taste, but not to extract the phenolic compounds of interest. In each test the technical treatment of the sample was similar. Extraction was carried out at room temperature (approximately 23 °C) for 30 minutes in a horizontal shaker with 200 rpm. Samples were weighed into extraction vials and solvent was added. The vials were closed with caps to minimise the evaporation of the extraction solvent. After 30 minutes the samples were filtered to separate the solvent from the solid. Filter papers were placed on aluminium foil and, after the solvent evaporahon, were removed. Extracted samples were dried at 100°C for 30 minutes to evaporate all the solvent traces. The solvents tested were chloroform, ethanol, diethylether, butanol, ethylacetate, heptane, n-hexane and cyclohexane and they were tested with different solvent/solid ratios. Methanol (MeOH) and acetonitrile (ACN) were not considered because of the high solubility of catechins and lignans to MeOH and ACN. The extracted phloem samples were tasted in the same way as the heated ones. Detailed results from each extraction experiment are presented in Table 14.2. [Pg.283]

When heated with a strong acid, pentoses and hexoses are dehydrated to form furfural and hydroxymethylfurfural derivatives respectively (Figure 9.20), the aldehyde groups of which will then condense with a phenolic compound to form a coloured product. This reaction forms the basis of some of the oldest qualitative tests for the detection of carbohydrates, e.g. the Molisch test using concentrated sulphuric acid and a-naphthol. [Pg.326]

Being a phenolic compound, isoxsuprine has been determined by a diversity of colorimetric methods. A colorimetric method was described for its determination in dosage forms, based on treatment with the nitrating mixture composed of 1 1 sulfuric and nitric acids [13], This mixture is heated at 100°C for 20 minutes, followed by the addition of acetone and NaOH. The yellow color produced is quantitated on the basis of its absorbance at 384 nm. [Pg.386]

Powdered plant material can also be extracted in a Soxhlet apparatus, first with hexane, for example, to remove lipids and then with ethyl acetate or ethanol to obtain phenolics. This approach is not suitable for heat-sensitive compounds. [Pg.2]

Current Methods. The general outline of the Kolbe-Schmitt reaction, as it is employed in the 1990s, is as follows. In the first step, phenol and hot aqueous caustic are mixed to produce the sodium phenate which is taken to dryness. Next, the phenate and dry carbon dioxide are introduced into the carbonator. Air is excluded to minimize oxidation and the formation of colored compounds. The gas—solid mixture is agitated and heated, first at low temperature, followed by several hours at higher temperatures, to complete the formation of sodium salicylate. Variations of this reaction have been noted in the literature and are still being investigated (10,11). One reported scheme produces salicylic acid or substituted salicylic acids by reaction of a granulated alkali metal salt of the respective phenolic compound with C02 in a fluidized bed at 20—130°C until at least 50—80% of the metal salt has been converted to... [Pg.286]

Lin et al. ( 6) measured the emulsion capacity of defatted sunflower seed products. Data in Table VII show that sunflower flour was superior in emulsifying capacity to all other products tested. The emulsions were in the form of fine foams and were stable during subsequent heat treatments. The diffusion-extraction processes employed to remove phenolic compounds dramatically reduced emulsion capacity, although isolating the protein improved emulsion capacity to some extent. [Pg.229]

Experiments were also carried out at 80 and lOO C. According to our observations at these high temperatures, solid- phase chemical transformations may take place between certain flavor constituents and cyclodextrin hydroxyls/monoterpene alcohols and phenolic compounds appear as a result of a solid-phase transacetylation of terpeneaoetates and phenyl-acetates with the simultaneous formation of cyclodextrin-acetates/. Long term heat treatments of cyclpdextrin-flavor complexes should not be run above 6o°C in order to avoid such phenomena. [Pg.152]

Uses. Furfuryl alcohol is widely used as a monomer in manufacturing furfuryl alcohol resins, and as a reactive solvent in a variety of synthetic resins and applications. Resins derived from furfuryl alcohol are the most important application for furfuryl alcohol in both utility and volume. The final cross-linked products display outstanding chemical, thermal, and mechanical properties. They are also heat-stable and remarkably resistant to acids, alkalies, and solvents. Many commercial resins of various compositions and properties have been prepared by polymerization of furfuryl alcohol and other co-reactants such as furfural, formaldehyde, glyoxal, resorcinol, phenolic compounds and urea. In 1992, domestic furfuryl alcohol consumption was estimated at 47 million pounds (38). [Pg.80]

Scalbert et al. (1989) used a slight modification of this method, whereby a 2.5 mL aliquot of the Folin-Ciocalteu reagent (diluted 10 times in water) and 2 mL of a 75g/L solution of sodium carbonate are added to 0.5 mL of the extract (diluted in methanol), followed by a 5 min. incubation in a 50°C waterbath. A potential complication of this method is the deglycosylation of phenolic compounds due to the heating. [Pg.153]

Polyphenylenoxide (PPO) Substituted phenols are used as monomers for the production of polyphenylenoxides, (PPOs) so they as well as phenolic degradation products can be found as emitted odor active compounds. In one case the odor of a PPO was predominantly caused by 2,6-dimethylphenol and trimethylanisol as well as by a tentatively identified substituted methoxypyrazine (Mayer and Breuer, 2004a). Another potent odorant derived from higher molecular phenolic compounds, antioxidants for example, by the influence of heat (>200 °C) and pressure is guaiacol (2-methoxyphenol) (Mayer and Breuer, 2006). [Pg.180]


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See also in sourсe #XX -- [ Pg.283 ]




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