Enzymatische Br�unung in Lebensmitteln

Substrate specificity of catechol oxidase from Lycopus europaeus and characterization of the bioproducts of enzymic caffeic acid oxidation1

“…The oxidation of VII leads to the quinones and the methides (VIII and IX). Both can eliminate CO P in position 2, producing X which was identi¢ed as 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-3-carboxynaphthaline (5). At basic pH it should be possible to obtain 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-2,3-dicarboxynaphthaline (XI).…”

“…Two types of phenolic browning reactions are known: (1) enzymic oxidation when a polyphenol oxidase is present [4,5];…”

Oxidation of caffeic acid in the presence of l-cysteine: isolation of 2-S-cysteinylcaffeic acid and evaluation of its antioxidant properties

“…The oxidation of caffeic acid but also other structurally similar components has been shown to proceed via the formation of o-quinones, which may spontaneously react and yield a spectrum of products (Cilliers & Singleton, 1991;Fulcrand, Cheminat, Brouillard, & Cheynier, 1994). These reactions are considered to be of high significance, since they are implicated in enzymic browning (Matheis, 1983;Mathew & Parpia, 1971;Saltveit, 2000), but also in processes that alter both the aesthetic and nutritional status of foods, by reacting with pigments (Cheynier, Souquet, Kontek, & Moutounet, 1994;Kader, Irmouli, Zitouni, Nicolas, & Metche, 1999;, amino acids (Friedman, 1996;Pierpoint, 1969), and proteins (Hurrel, Finot, & Cuq, 1982;Kroll & Rawel, 2001;Rawel, Kroll, & Riese, 2000).…”

Some kinetic properties of polyphenol oxidase obtained from dill (Anethum graveolens)

“…The main step in enzymatic browning is the oxidation of phenolic compounds to corresponding quinones by PPO in the presence of oxygen. The quinones then condense to form darkened pigments [9,10]. These reactions known as enzymatic browning are not generally desirable for the food industry, but can be used for preparation of dark tea.…”