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Browning reactions

To a solution of 0.30 mol of ethyllithium (note 1) in about 270 ml of diethyl ether (see Chapter II, Exp. 1) v/as added 0.30 mol of methoxyallene at -20°C (see Chapter IV, Exp. 4) at a rate such that the temperature could be kept between -15 and -2Q°C. Fifteen minutes later a mixture of 0.27 mol of >z-butyl bromide and 100 ml of pure, dry HMPT ivas added in 5 min with efficient cooling, so that the temperature of the reaction mixture remained below 0°C. The cooling bath was then removed and the temperature was allowed to rise. After 4 h the brown reaction mixture was poured into 200 ml of ice-water. The aqueous layer was extracted twice with diethyl ether. The combined solutions were washed with concentrated ammonium chloride solution (which had been made slightly alkaline by addition of a few millilitres of aqueous ammonia, note 2) and dried over potassium carbonate. After addition of a small amount (2-5 ml) of... [Pg.37]

Note 1. If commercial BuLi in hexane is used with diethyl ether or THF as cosolvent, a dark brown reaction mixture is formed, from which the desired product can be isolated in lower yields. [Pg.46]

The addition took 30-40 min. The temperature of the reaction mixture was then allowed to rise gradually to -20°C over 30 min and the brown reaction mixture was poured into 200 ml of water. After shaking, the upper layer was separated off and the aqueous layer was extracted four times with small portions of diethyl ether. [Pg.131]

Browning Reactions. The fluorescent components formed in the browning reaction (8) of peroxidized phosphatidylethanolamine are produced mainly by interaction of the amine group of PE and saturated aldehydes produced through the decomposition of fatty acid hydroperoxides. [Pg.99]

MaillardReaction (Nonenzymatic Glycation), Browned reaction products ate formed by heating amino acid and simple sugar. This reaction is important in food science relating to coloring, taste, and flavor enhancement (79), and is iUustrated as follows ... [Pg.280]

Amino acids play a role in food processing in the development of a cooked flavor as the result of a chemical reaction called the nonenzymatic browning reaction (228). [Pg.296]

Fmctose is a highly reactive molecule. When stored in solution at high temperatures, fmctose not only browns rapidly but also polymeri2es to dianhydrides [38837-99-9] [50692-21-2] [50692-22-3] [50692-23-4] [50692-24-5]. Fmctose also reacts rapidly with amines and proteins in the nonen2ymatic or MaiUard browning reaction (5). This is a valued attribute in baked food products where cmst color is important. An appreciation of these properties allows the judicious choice of conditions under which fmctose can be used successfully in food appHcations. [Pg.44]

Addition of BuLi to a 0.3 M solution of chloromethyl phenyl sulfoxide in THF at — 78 "C yields an immediate bright-yellow solution containing the lithio derivative which is stable for at least 2 h at —78 rC. Decomposition occurs rapidly above —20 C with the solution becoming turbid and the color changing to dark brown. Reaction of the lithiated solution of chloromethyl phenyl sulfoxide with cyclohexanone, acetone, or ben/ophenone for 10 min at —78 °C followed by 30 min at —20 rC yields one diastereomeT in 79, 75 and 68 % yields, respectively, after hydrolysis of the corresponding adducts. [Pg.649]

For many situations, a simple total anthocyanin determination is inappropriate because of interference from polymeric anthocyanins, anthocyanin degradation products, or melanoidins from browning reactions. In those cases, the approach has been to measure the absorbance at two different pH values. The differential method measures the absorbance at two pH valnes and rehes on structural transformations of the anthocyanin chromophore as a function of pH. Anthocyanins switch from a saturated bright red-bluish color at pH 1 to colorless at pH 4.5. Conversely, polymeric anthocyanins and others retain their color at pH 4.5. Thus, measurement of anthocyanin samples at pH 1 and 4.5 can remove the interference of other materials that may show absorbance at the A is-max-... [Pg.484]

Selected clay stabilizers are shown in Table 1-10. Thermal-treated carbohydrates are suitable as shale stabilizers [1609-1611]. They may be formed by heating an alkaline solution of the carbohydrate, and the browning reaction product may be reacted with a cationic base. The inversion of nonreducing sugars may be first effected on selected carbohydrates, with the inversion catalyzing the browning reaction. [Pg.20]

J. J. Sheu andR. G. Bland. Drilling fluid with browning reaction anionic carbohydrate. Patent US 5106517, 1992. [Pg.460]

Microbial growth, enzymatic reactions, non-enzymatic browning (reaction between carbonyl and amino compounds), and lipid oxidation are the major deterioration mechanisms that limit the stability of low moisture (o intermediate moisture foods (o.6o < <0.85) and biological materials. [Pg.39]

Monosaccharides are probably involved in the browning reactions that occur during the roasting of coffee. Caramelization involving the sugars alone, and Maillard reactions, between sugars and free amino acids, produce polymeric yellow to dark brown substances, known as melanoidins. These melanoidins can be extracted into hot water, separated and characterized.105... [Pg.141]

Abiotic spoilage is produced by different physical and chemical changes such as hydrolytic action of enzymes, oxidation of fats, breakdown of proteins, and a browning reaction between proteins and sugars. However, in this chapter we focus on microbial deterioration and their effects on bioactive compounds. [Pg.343]

The reaction of a primary amine with lactose is accompanied by a browning of the solids, and the path of such reactions is easily following by means of diffuse reflectance spectroscopy. For instance, the reaction of isonicotinic acid hydrazide (Isoniazid) with lactose could be followed through changes in the reflectance spectrum [31]. As may be seen in Fig. 4, a steady decrease in reflectance was noted as the sample was heated for increasing amounts of time. The spectral data were used to deduce the rate constants for the browning reaction at various heating temperatures, and these rates could be correlated with those... [Pg.46]

The dark red-brown reaction mixture is cautiously poured onto a mixture of 2 kg. of ice and 200 ml. of concentrated hydrochloric acid. [Pg.4]

Sherwin, C.P. and Labuza, T.P. 2003. Role of moisture in maillard browning reaction rate in intermediate moisture foods Comparing solvent phase and matrix properties. J. Food Sci. 68, 588-594. [Pg.98]


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Alkynes, Brown hydroboration reaction

Amine-lipid browning reaction

Amino browning reactions

Antioxidant browning reaction products

Ascorbic browning reaction

Assay browning reaction

BROWN Acetylene Zipper Reaction

Bread browning reaction

Brown hydroboration reaction

Brown hydroboration reaction mechanism

Brown-Walker reaction

Browning reaction Maillard

Browning reaction amino acids

Browning reaction and color

Browning reaction catalyst, transition

Browning reaction degradation products

Browning reaction inhibition

Browning reaction nutritional aspects

Browning reaction nutritive value

Browning reaction prevention

Browning reaction products, flavor

Browning reaction systems

Browning reactions hydrophilization

Browning reactions in food

Browning reactions, polyphenol oxidase

Crum Brown-Walker reaction

Effect of browning reaction

Enzymatic browning reactions

Flavor browning reactions

Lysine browning reaction

Lysine browning, reactions during

Non-enzymatic browning reactions

Non-enzymic browning reaction

Nonenzymatic browning Maillard reaction

Nonenzymatic browning reactions

Of browning reaction

Oxidation reactions Brown hydroboration reaction

Polyphenol browning reactions

Products of Browning Reactions

Regioselectivity Brown hydroboration reaction

Ribose/phosphate reaction browning

Stability browning reactions

Sugar-amine browning reaction

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