Photochemial Degradation of Betanine and Selected Anthocyanins

Abstract

The effect of fluorescent light on the degradation rates of betanine and the major cranberry anthocyanins was determined in model systems. Degradation rates were measured in the presence of oxygen in a temperature range 25-55°C. Retained pigment was separated and quantified by high performance liquid chromatography. Light had a minimal effect at 55°C because of considerable thermal destruction. However, at 40°C for anthocyanins and 25°C for betanine, light was responsible for most of the degradation occurring. Light increased rates of anthocyanin degradation more than those of betanine. Molecular oxygen was necessary for light to have a significant effect.

Effects of heat, pH, antioxidant, agitation and light on betacyanin stability using red-fleshed dragon fruit (Hylocereus polyrhizus) juice and concentrate as models

“…3). Stability of betalain is influenced by light (UV or visible) because it excites the π electron of betalain chromophores to a higher energy state (π*), resulting in lower activation energy and thus higher reactivity of the molecule (Attoe and von Elbe 1981;Jackman and Smith 1996). Unlike juice samples, betacyanin content of concentrate sample was not significant different (p>0.05) between storage under light or dark (Fig.…”

“…3). Attoe and von Elbe (1981) reported that as pigment concentration increased, the influence of light on the degradation of betanin was negligible. This could possibly explain the negligible effect of light on the degradation of betacyanin in the concentrated sample.…”

Efeitos de interações intermoleculares sobre as propriedades fotofísicas de betalaínas naturais

“…Betalaínas são compostos sensíveis a fatores como irradiação luminosa intensa, 40 alta atividade de água, [41][42] extrema acidez ou basicidade [43][44][45] e altas temperaturas 44,[46][47] .…”

“…Apesar da presença de luz induzir a formação de betalaínas in vivo, [49][50][51][52] a irradiação de betalaínas em solução favorece a sua decomposição. 40,53 Luz na região UV-vis favorece a decomposição de betalaínas através de processos oxidativos, i.e., E a = 104,5 kJ mol -1 no escuro e 80,3 kJ mol -1 sob iluminação. 40,44,[54][55][56] Esquema 5: Possíveis vias de degradação de betacianinas.…”

“…40,53 Luz na região UV-vis favorece a decomposição de betalaínas através de processos oxidativos, i.e., E a = 104,5 kJ mol -1 no escuro e 80,3 kJ mol -1 sob iluminação. 40,44,[54][55][56] Esquema 5: Possíveis vias de degradação de betacianinas. 48,57 Na betanina, ligações duplas em vermelho são sujeitas à isomerização, ligações em azul podem sofrer isomerização e ligações em verde são passíveis de oxidação para formação de dupla ligação.…”