Search

Carotenoids are used in wide-ranging food applications, but they are susceptible to degradation by many factors including light. We examined the photodegradation of five kinds of carotenoids and three kinds of anthocyanins to clarify which structures of pigments were favorable to accelerated degradation by sulfides under UVA irradiation. Under UVA irradiation, crocetin and crocin were decomposed more rapidly in the presence of dimethyl tetrasulfide than in the absence of the sulfide, but not as rapidly as beta-carotene, zeaxanthin and beta-cryptoxanthin were. However, cyanidin was decomposed more slowly in the presence of sulfide than in the absence of sulfide. Moreover, the photodegradation of kuromanin and keracyanin was not affected by the addition of a sulfide. We also examined the mechanism for this accelerated degradation. Normal hexane was more favorable to the photodegradation of beta-carotene than methanol and ethanol. The accelerated degradation was inhibited by free radical scavengers, but enhanced by the addition of deuterium oxide. These results suggest that conjugated double bonds were favorable to the accelerated photodegradation by sulfide and that this reaction was mediated by free radicals.

The photodegradation of carotenoids by UVA irradiation in the presence of sulfides was investigated. The sulfides accelerated the photodegradation of carotenoids. A larger number of sulfur atoms of coexistent sulfides was more favorable to the acceleration effect of sulfides on the photodegradation of beta-carotene, but the alk(en)yl group of sulfides was less favorable to the acceleration effect of sulfur compounds. The acceleration effect depended on light intensity, temperature, and the initial concentrations of beta-carotene and sulfide.

Liposomes, in which beta-carotene, beta-cryptoxanthin, zeaxanthin, beta-cryptoxanthin palmitate or beta-cryptoxanthin acetate had been embedded, were irradiated by UVA, and the rate of degradation of each carotenoid was measured. There was no significant difference in the degradation rate between beta-carotene, beta-cryptoxanthin and zeaxanthin. The degradation rates of beta-cryptoxanthin palmitate and beta-cryptoxanthin acetate were faster than that of beta-cryptoxanthin, and the degradation rate of beta-cryptoxanthin palmitate was faster than that of beta-cryptoxanthin acetate.

Investigates the reduction in photostability by the esterification of beta-Cryptoxanthin. Degradation rates of beta-cryptoxanthin palmitate and acetate faster than that of beta-cryptoxanthin.